Difference between revisions of "Clock device tree configuration - Bootloader specific"

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m (Reverted edits by Patrick Delaunay (talk) to last revision by NICOLAS LE BAYON)
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m (HSI and CSI clocks calibration)
 

1 Article purpose[edit]

This article describes the specific RCC internal peripheral configuration done by the first stage bootloader. :

Warning.png This article explains how to configure the clock tree in the RCC at boot time.
You can then refer to the clock device tree configuration article to understand how to derive each internal peripheral clock tree in Linux® OS from the RCC clock tree.

The configuration is performed using the device tree mechanism that provides a hardware description of the RCC peripheral.

This clock tree is only used in the device tree of the boot chain FSBL; so in the TF-A device tree for OpenSTLinux official delivery (or in SPL only for the DDR tuning tool).

Even if the clock tree information is also present in the U-Boot device tree, it is not used during boot by this SSBL.

2 DT bindings documentation[edit]

The bootloader clock device tree bindings are composed of correspond to the vendor clock DT bindings used by the clk-stm32mp1 driver of the FSBL (TF-A and by the or U-Boot SPL driver. ), it is based on:

This binding document explains how to write device tree files for clocks on bootloader side:

  • TF-A: <TFtf-A directory>a/docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt"[1]
  • U-Boot SPL: doc/device-tree-bindings/clock/st,stm32mp1.txt[12]
Info.png Please note that the upstreaming of this TF-A file is in progress

3 DT configuration[edit]

This hardware description is a combination of the STM32 microprocessor device tree files (.dtsi extension) and board device tree files (.dts extension). See the Device tree for an explanation of the device tree file split.

STM32CubeMX can be used to generate the board device tree. Refer to How to configure the DT using STM32CubeMX for more details.

3.1 DT configuration (STM32 level)[edit]

The STM32MP1 clock nodes are located in stm32mp157c.dtsi[23] (see Device tree for more explanations):

Please refer to clock device tree configuration for the bindings common with Linux® kernel.

 / {
 ...
 	clocks {
 		clk_hse: clk-hse {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <24000000>;
 		};
 
 ...
   	};
 ...
 	soc {
 ...
 		rcc: rcc@50000000 {
 			compatible = "st,stm32mp1-rcc", "syscon";
 			reg = <0x50000000 0x1000>;
 			#clock-cells = <1>;
 			#reset-cells = <1>;
 			interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;
 		};
...
 
 	};
 
 };

Please refer to clock device tree configuration for the bindings common with Linux® kernel.

3.2 DT configuration (board level)[edit]

3.2.1 Clock node[edit]

The clock tree is also based on five fixed clocks in the clock node. They are used to define the state of associated ST32MP1 oscillators:

  • clk-lsi
  • clk-lse
  • clk-hsi
  • clk-hse
  • clk-csi.

Please refer to clock device tree configuration for detailed information.

At boot time, the clock tree initialization performs the following tasks:

  • enabling of the oscillators present in the device tree and not disabled (node with status="disabled"),
  • disabling of the HSI oscillator if the node is absent or disabled (HSI is always activated by bootROMthe ROM code).

This information is located in the following files:

  • STM32MP157C-ED1 and STM32MP157C-EV1:
    • TF-A: fdts/stm32mp157c-ed1.dts[34]
    • U-Boot SPL: arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi[45]
  • STM32MP157XSTM32MP157A-DK1 and STM32MP157XSTM32MP157C-DK2:
    • TF-A: <TF-A directory>/fdts/stm32mp157a-dk1.dts[6].
    • U-Boot SPL: < U-Boot directory>/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi.
Info.png Please note that the upstreaming of these two TF-A / U-Boot SPL files is in progress

Optional properties are described below.

3.2.1.1 Optional properties for "clk-lse" and "clk-hse" external oscillators[edit]

For external oscillator HSE and LSE, the default clock configuration is an external crystal/ceramic resonator.

Four optional fields are supported:

  • "st,bypass" configures the oscillator bypass mode (external analog clock source (set HSEBYP, LSEBYP),
  • "st,digbypass" configures the bypass mode as full-swing digital signal (DIGBYPexternal digital clock source (set DIGBYP and HSEBYP, LSEBYP),
  • "st,css" activates the clock security system (HSECSSON, LSECSSON),
  • "st,drive" (LSE only) contains the value of the drive for the oscillator (see LSEDRV_ defined in the file stm32mp1-clksrc.h[58]).

Below an example of board file:

3.2.1.2 DT configuration for HSE[edit]

The HSE can accept an external crystal/ceramic or external clock source on OSC_IN, digital or analog : the user needs to select the correct frequency and the correct configuration in the device tree, corresponding to the hardware setup.

All the ST boards are using a digital external clock configuration (so device tree with = st,digbypass).

For example with the same 24MHz frequency, we have 3 configurations:

Hse config.jpg
  • Digital external clock = st,digbypass
 	/ {
 		clocks {
 			clk_hse: clk-hse {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <24000000><24000000>;
 				st,digbypass;
 			};
 	};

  • Analog external clock = st,bypass
 	/ {
 		clocks {
 			clk_hse: clk-hse {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <24000000>;
 				st,bypass;
			};
 	};

  • Crystal/ ceramic resonators configuration
 	/ {
 		clocks {
 			clk_hse: clk-hse {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <24000000>;
 			};
 	};

3.2.1.3 DT configuration for LSE[edit]

Below an example of LSE on board file with 32,768kHz crystal resonators, the drive set to medium high and with activated clock security system.

 	/ {
 		clocks {
 			clk_lse: clk-lse {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <32768><32768>;
 				st,css;
 				st,drive = <LSEDRV_LOWEST><LSEDRV_MEDIUM_HIGH>;
 			};
 	};
3.2.1.24 Optional property for "clk-hsi" internal oscillator[edit]

The HSI clock frequency is internally fixed to 64 MHz for STM32MP15 devices.

In the device tree, clk-hsi is the clock after HSIDIV divider (more information on clk_hsi can be found in the RCC chapter in the reference manual).
As a result the frequency of this fixed clock is used to compute the expected HSIDIV for the clock tree initialization.

Below an example with HSIDIV = 1/1:

 	/ {
 		clocks {
 			clk_hsi: clk-hsi {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <64000000>;
 			};
 	};

Below an example with HSIDIV = 1/2:

 	/ {
 		clocks {
 			clk_hsi: clk-hsi {
 				#clock-cells = <0>;
 				compatible = "fixed-clock";
 				clock-frequency = <32000000>;
 			};
 	};
3.2.1.5 Clock node example[edit]

An example of clocks node with:

  • all oscillators switched on (HSE, HSI, LSE, LSI, CSI)
  • HSI at 64MHZ (HSIDIV = 1/1)
  • HSE using a digital external clock at 24MHz
  • LSE using an external crystal a 32.768kHz (the typical frequency)

We highlight the customized parts:

 / {
 	clocks {
 		clk_hse: clk-hse {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <24000000>;
 			st,digbypass;
 		};
 
 		clk_hsi: clk-hsi {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <64000000>;
 		};
 
 		clk_lse: clk-lse {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <32768>;
 		};
 
 		clk_lsi: clk-lsi {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <32000>;
 		};
 
 		clk_csi: clk-csi {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <4000000>;
 		};
 	};
 };

So the resulting board device tree, based on SoC device tree "stm32mp157c.dtsi", is :

 #include "stm32mp157c.dtsi"
 &clk_hse {
 	clock-frequency = <24000000>;
 	st,digbypass;
 };
 
 &clk_hsi {
 	clock-frequency = <64000000>;
 };
 
 &clk_lse {
 	clock-frequency = <32768>;
 };

It is the configuration used by TF-A for STM32MP157C-EV1 [4]

3.2.2 STM32MP1 clock node[edit]

Please refer to clock device tree configuration for information on how to specify the number of cells in a clock specifier.

The bootloader performs a global clock initialization, as described below. The information related to a given board can be found in the board specific device tree files listed in clock node.

The bootloader uses other properties for RCC node ("st,stm32mp1-rcc" compatible):

  • secure-status: related to TZEN bit configuration in RCC_TZCR register that allows to restrict RCC register and PWR registers write access
  • st,clksrc: clock source configuration array
  • st,clkdiv: clock divider configuration array
  • st,pll: specific PLL configuration
  • st,pkcs: peripheral kernel clock distribution configuration array.

All the available clocks are defined as preprocessor macros in stm32mp1-clks.h[69] and can be used in device tree sources.

3.2.2.1 Defining clock source distribution with st,clksrc property[edit]

This property can be used to configure the clock distribution tree. When used, it must describe the whole distribution tree.

There are nine clock source selectors for the STM32MP15 devices. They must be configured in the following order: MPU, AXI, MCU, PLL12, PLL3, PLL4, RTC, MCO1, and MCO2.

The clock source configuration values are defined by the CLK_<NAME>_<SOURCE> macros located in stm32mp1-clksrc.h[58].

Example:

        st,clksrc = <
                CLK_MPU_PLL1P
                CLK_AXI_PLL2P
                CLK_MCU_PLL3P
                CLK_PLL12_HSE
                CLK_PLL3_HSE
                CLK_PLL4_HSE
                CLK_RTC_LSE
                CLK_MCO1_DISABLED
                CLK_MCO2_DISABLED
        >;
3.2.2.2 Defining clock dividers with st,clkdiv property[edit]

This property can be used to configure the value of the clock main dividers. When used, it must describe the whole clock divider tree.

There are 11 dividers values for the STM32MP15 devices. They must be configured in the following order: MPU, AXI, MCU, APB1, APB2, APB3, APB4, APB5, RTC, MCO1 and MCO2.

Each divider value uses the DIV coding defined in the RCC associated register, RCC_xxxDIVR. In most cases, this value is the following:

  • 0x0: not divided
  • 0x1: division by 2
  • 0x2: division by 4
  • 0x3: division by 8
  • ...

Note that the coding differs for RTC MCO1 and MCO2:

  • 0x0: not divided
  • 0x1: division by 2
  • 0x2: division by 3
  • 0x3: division by 4
  • ...

Example:

        st,clkdiv = <
                1 /*MPU*/
                0 /*AXI*/
                0 /*MCU*/
                1 /*APB1*/
                1 /*APB2*/
                1 /*APB3*/
                1 /*APB4*/
                2 /*APB5*/
                23 /*RTC*/
                0 /*MCO1*/
                0 /*MCO2*/
        >;
3.2.2.3 Defining peripheral PLL frequencies with st,pll property[edit]

This property can be used to configure PLL frequencies.

PLL children nodes for PLL1 to PLL4 (see reference manual for details) are associated with an index from 0 to 3 (st,pll@0 to st,pll@3). PLLx is off when the associated node is absent.

Below the available properties for each PLL node:

  • cfg contains the PLL configuration parameters in the following order: DIVM, DIVN, DIVP, DIVQ, DIVR, output.
DIVx values are defined as in RCC:
  • 0x0: bypass (division by 1)
  • 0x1: division by 2
  • 0x2: division by 3
  • 0x3: division by 4
  • ...
Output contains a bitfield for each output value (1:ON / 0:OFF)
  • BIT(0) → output P : DIVPEN
  • BIT(1) → output Q : DIVQEN
  • BIT(2) → output R : DIVREN
Note: PQR(p,q,r) macro can be used to build this value with p, q, r = 0 or 1.
  • frac: fractional part of the multiplication factor (optional, when absent PLL is in integer mode).
  • csg contains the clock spreading generator parameters (optional) in the following order: MOD_PER, INC_STEP and SSCG_MODE.
MOD_PER: modulation period adjustment
INC_STEP: modulation depth adjustment
SSCG_MODE: Spread spectrum clock generator mode, defined in stm32mp1-clksrc.h[58]:
  • SSCG_MODE_CENTER_SPREAD = 0
  • SSCG_MODE_DOWN_SPREAD = 1

Example:

	st,pll@0 {
		cfg = < 1 53 0 0 0 1 >;
		frac = < 0x810 >;
	};
	st,pll@1 {
		cfg = < 1 43 1 0 0 PQR(0,1,1) >;
		csg = < 10 20 1 >;
	};
	st,pll@2 {
		cfg = < 2 85 3 13 3 0 >;
		csg = < 10 20 SSCG_MODE_CENTER_SPREAD >;
	};
	st,pll@3 {
		cfg = < 2 78 4 7 9 3 >;
	};
3.2.2.4 Defining peripheral kernel clock tree distribution with st,pkcs property[edit]

This property can be used to configure the peripheral kernel clock selection.

It is a list of peripheral kernel clock source identifiers defined by the CLK_<KERNEL-CLOCK>_<PARENT-CLOCK> macros in the stm32mp1-clksrc.h[58] header file.

st,pkcs may not list all the kernel clocks. No specific order is required.

Example:

	st,pkcs = <
		CLK_STGEN_HSE
		CLK_CKPER_HSI
		CLK_USBPHY_PLL2P
		CLK_DSI_PLL2Q
                CLK_I2C46_HSI
                CLK_UART1_HSI
                CLK_UART24_HSI
	>;
3.2.2.5 HSI and CSI clock clocks calibration[edit]

Calibration The calibration is an optional feature that can be enabled from the device tree. It allows requesting the HSI or CSI clock calibration by several means:

  • SiP SMC service
  • Periodic calibration every X seconds
  • Interrupt raised by the MCU

This feature requires that a hardware timer is assigned to the calibration sequence.

A dedicated interrupt must be defined using "mcu_sev" name to start a calibration on detection of an interrupt raised by the MCU.

  • st,hsi-cal: used to enable HSI clock calibration feature.
  • st,csi-cal; used to enable CSI clock calibration feature.
  • st,cal-sec: used to enable periodic calibration at specified time intervals from the secure monitor. The time interval must be given in seconds. If not specified, a calibration is only processed for each incoming request.

Example:

	&rcc {
		st,hsi-cal;
		st,csi-cal;
		st,cal-sec = <15>;
		secure-interrupts = <GIC_SPI 144 IRQ_TYPE_LEVEL_HIGH>,
				<GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>;
		interrupt-names = "mcu_sev", "wakeup";
	};

4 How to configure the DT using STM32CubeMX[edit]

The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.

The STM32CubeMX may not support all the properties described in the above DT bindings documentation paragraph.
If so, the tool inserts user sections in the generated device tree.
These sections can then be edited to add some properties and they are preserved from one generation to another.

Refer to STM32CubeMX user manual for further information.

5 References[edit]

Please refer to the following links for additional information:

  1. docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt TF-A clock binding information file
  2. doc/device-tree-bindings/clock/st,stm32mp1.txt U-Boot SPL clock binding information file
  3. fdts/stm32mp157c.dtsi (for TF-A), arch/arm/dts/stm32mp157c.dtsi (for U-Boot SPL): STM32MP157C device tree files
  4. 4.0 4.1 fdts/stm32mp157c-ed1.dts STM32MP157C-ED1 device tree file for TF-A
  5. arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi STM32MP157C-ED1 device tree file for U-Boot SPL
  6. 5.0 5.1 5.2 5
  7. fdts/stm32mp157a-dk1.dts STM32MP157A-DK1 device tree file for TF-A
  8. arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi STM32MP157C-DK1 device tree file for U-Boot SPL
  9. 8.0 8.1 8.2 8.3 include/dt-bindings/clock/stm32mp1-clksrc.h (for TF-A), include/dt-bindings/clock/stm32mp1-clksrc.h (for U-Boot SPL): STM32MP1 DT bindings clock source files
  10. include/dt-bindings/clock/stm32mp1-clks.h (for TF-A), include/dt-bindings/clock/stm32mp1-clks.h (for U-Boot SPL): STM32MP1 DT bindings clock identifier files



<noinclude>

{{ArticleBasedOnModel | [[Contributors:Peripheral or framework device tree configuration model]]}}
{{ArticleMainWriter | NicolasLB}}
{{ArticleApprovedVersion | NicolasLB | LionelD, YannG, PatrickD, GeraldB | No previous approved version | AnneJ - 04Feb'19 - 10612 | 24 January'19}}
[[Category:Device tree configuration]]
[[Category:Trusted Firmware-A (TF-A)]]
[[Category:U-Boot]]</noinclude>

== Article purpose ==

This article describes the specific [[RCC internal peripheral|'''RCC''' internal peripheral]] configuration done by the [[Boot chains overview|first stage bootloader]].
: 
* [[TF-A overview|TF-A]] for the Trusted boot chain
* [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] for the Basic boot chain
{{Warning|This article explains how to configure the clock tree in the [[RCC_internal_peripheral|RCC]] at boot time.<br/>You can then refer to the [[Clock device tree configuration|clock device tree configuration]] article to understand how to derive each internal peripheral clock tree in Linux<sup>&reg;</sup> OS from the [[RCC_internal_peripheral|RCC]] clock tree.}}

The configuration is performed using the [[Device tree|device tree]] mechanism that provides a hardware description of the [[RCC_internal_peripheral|RCC]] peripheral.
This clock tree is only used in the device tree of the boot chain FSBL; so in the TF-A device tree for OpenSTLinux official delivery (or in SPL only for the DDR tuning tool).

Even if the clock tree information is also present in the [[U-Boot_overview|U-Boot]] device tree, it is not used during boot by this SSBL.
== DT bindings documentation ==

The bootloader clock device tree bindings are composed of correspond to the vendor clock DT bindings used by the clk-stm32mp1 driver of the FSBL ([[TF-A overview|TF-A]] and by the or [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] driver. 
), it is based on:
*  binding described in [[Clock_device_tree_configuration]]
*  bootloader specific properties described in [[#DT configuration]]
This binding document explains how to write device tree files for clocks on bootloader side:
* [[TF-A overview|TF-A]]: ''<TF-A directory>tf-a/docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt''"<ref name="st,stm32mp1-rcc.txt"> {{CodeSource | TF-A | docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt}} [[TF-A overview|TF-A]] clock binding information file</ref>
* [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''doc/device-tree-bindings/clock/st,stm32mp1.txt''<ref name="st,stm32mp1.txt">{{CodeSource | U-Boot | doc/device-tree-bindings/clock/st,stm32mp1.txt}} [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] clock binding information file</ref>

{{Info|Please note that the upstreaming of this [[TF-A overview|TF-A]] file is in progress}}
== DT configuration ==
This hardware description is a combination of the '''STM32 microprocessor''' device tree files (''.dtsi'' extension) and '''board''' device tree files (''.dts'' extension). See the [[Device tree]] for an explanation of the device tree file split.

'''STM32CubeMX''' can be used to generate the board device tree. Refer to [[#How_to_configure_the_DT_using_STM32CubeMX|How to configure the DT using STM32CubeMX]] for more details.

=== DT configuration (STM32 level) ===
The STM32MP1 clock nodes are located in ''stm32mp157c.dtsi''<ref name="stm32mp157_pin_dtsi">{{CodeSource | TF-A | fdts/stm32mp157c.dtsi}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot| arch/arm/dts/stm32mp157c.dtsi }} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP157C device tree files</ref> (see [[Device tree]] for more explanations):
* fixed-clock definedefined in [[#clock node|clock node]]
* [[RCC_internal_peripheral|RCC]] node for [[#STM32MP1 Clockclock node]]: clock generation and distribution.
Please refer to [[Clock device tree configuration|clock device tree configuration]] for the bindings common with Linux<sup>&reg;</sup> kernel.
  / {
  ...
  	clocks {
  		clk_hse: clk-hse {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <24000000>;
  		};

  ...
    	};
  ...
  	soc {
  ...
  		rcc: rcc@50000000 {
  			compatible = "st,stm32mp1-rcc", "syscon";
  			reg = <0x50000000 0x1000>;
  			#clock-cells = <1>;
  			#reset-cells = <1>;
  			interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;
  		};
 ...

  	};

  };
Please refer to [[Clock device tree configuration|clock device tree configuration]] for the bindings common with Linux<sup>&reg;</sup> kernel.
=== DT configuration (board level) ===
==== Clock node ====
The clock tree is also based on five fixed clocks in the clock node. They are used to define the state of associated ST32MP1 oscillators:
* clk-lsi
* clk-lse
* clk-hsi
* clk-hse
* clk-csi.

Please refer to [[Clock device tree configuration|clock device tree configuration]] for detailed information.

At boot time, the clock tree initialization performs the following tasks:
* enabling of the oscillators present in the device tree and not disabled (node with status="disabled"),
* disabling of the HSI oscillator if the node is absent (or disabled (HSI is always activated by bootROMthe ROM code).

This information is located in the following files:
* STM32MP157C-ED1 and STM32MP157C-EV1:
** [[TF-A overview|TF-A]]: ''fdts/stm32mp157c-ed1.dts''<ref name="stm32mp157c-ed1">{{CodeSource | TF-A | fdts/stm32mp157c-ed1.dts}} STM32MP157C-ED1 device tree file for [[TF-A overview|TF-A]]</ref>

** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi''<ref name="stm32mp157c-ed1-u-boot">{{CodeSource | U-Boot | arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi}} STM32MP157C-ED1 device tree file for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]</ref>

* STM32MP157XSTM32MP157A-DK1 and STM32MP157XSTM32MP157C-DK2: 
** [[TF-A overview|TF-A]]: ''<TF-A directory>/fdts/stm32mp157a-dk1.dts''.<ref name="stm32mp157c-dk1">{{CodeSource | TF-A | fdts/stm32mp157a-dk1.dts}} STM32MP157A-DK1 device tree file for [[TF-A overview|TF-A]]</ref>.** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''< U-Boot directory>/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi''.
{{Info|Please note that the upstreaming of these two [[TF-A overview|TF-A]] / <ref name="stm32mp157a-dk1-u-boot">{{CodeSource | U-Boot | arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi}} STM32MP157C-DK1 device tree file for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] files is in progress}}
</ref>.
Optional properties are described below.

===== Optional properties for "clk-lse" and "clk-hse" external oscillators =====

For external oscillator HSE and LSE, the default clock configuration is an external crystal/ceramic resonator.
Four optional fields are supported:
* "st,bypass" configures the oscillator bypass mode (external analog clock source (set HSEBYP, LSEBYP),
* "st,digbypass" configures the bypass mode as full-swing digital signal (DIGBYPexternal digital clock source (set DIGBYP and HSEBYP, LSEBYP),
* "st,css" activates the clock security system (HSECSSON, LSECSSON),
* "st,drive" (LSE only) contains the value of the drive for the oscillator (see LSEDRV_ defined in the file ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc">{{CodeSource | TF-A | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP1 DT bindings clock source files</ref>).
Below an example of board file:<pre>

	/ {
		clocks {===== DT configuration for HSE =====

The HSE can accept an external crystal/ceramic or external clock source on OSC_IN, digital or analog : the user needs to select the correct frequency and the correct configuration in the device tree, corresponding to the hardware setup.

All the ST boards are using a digital external clock configuration (so device tree with = st,digbypass).

For example with the same 24MHz frequency, we have 3 configurations:

[[File:Hse config.jpg|800px|none|]]

* Digital external clock = st,digbypass
  	/ {
  		clocks {			clk_hse: clk-hse {  				#clock-cells = <0>;  				compatible = "fixed-clock";  				clock-frequency = <24000000>;
				st,bypass;
			};

			clk_lse: clk-lse {
				#clock-cells = <0>;
				compatible = "fixed-clock";
				clock-frequency = <32768>;
				st,css;
				st,drive = <LSEDRV_LOWEST>;
			};
	};</pre>

<{{Highlight|24000000}}>;
  				{{Highlight|st,digbypass;}}
  			};
  	};

* Analog external clock = st,bypass
  	/ {
  		clocks {
  			clk_hse: clk-hse {
  				#clock-cells = <0>;
  				compatible = "fixed-clock";
  				clock-frequency = <{{Highlight|24000000}}>;
  				{{Highlight|st,bypass;}}
 			};
  	};

* Crystal/ ceramic resonators configuration
  	/ {
  		clocks {
  			clk_hse: clk-hse {
  				#clock-cells = <0>;
  				compatible = "fixed-clock";
  				clock-frequency = <{{Highlight|24000000}}>;
  			};
  	};

===== DT configuration for LSE =====

Below an example of LSE on board file with 32,768kHz crystal resonators, the drive set to medium high and with activated clock security system.

  	/ {
  		clocks {
  			clk_lse: clk-lse {
  				#clock-cells = <0>;
  				compatible = "fixed-clock";
  				clock-frequency = <{{Highlight|32768}}>;
  				{{Highlight|st,css;}}
  				st,drive = <{{Highlight|LSEDRV_MEDIUM_HIGH}}>;
  			};
  	};
===== Optional property for "clk-hsi" internal oscillator =====
The HSI clock frequency is internally fixed to 64 MHz for STM32MP15 devices.

In the device tree, clk-hsi is the clock after HSIDIV divider (more information on clk_hsi can be found in the RCC chapter in the [[STM32MP15 resources|reference manual]]).<br/>

As a result the frequency of this fixed clock is used to compute the expected HSIDIV for the clock tree initialization.

Below an example with HSIDIV = 1/1:

  	/ {
  		clocks {
  			clk_hsi: clk-hsi {
  				#clock-cells = <0>;
  				compatible = "fixed-clock";
  				clock-frequency = <{{Highlight|64000000}}>;
  			};
  	};

Below an example with HSIDIV = 1/2:
  	/ {
  		clocks {
  			clk_hsi: clk-hsi {
  				#clock-cells = <0>;
  				compatible = "fixed-clock";
  				clock-frequency = <{{Highlight|32000000}}>;
  			};
  	};

==== = Clock node example =====

An example of clocks node with:
* all oscillators switched on (HSE, HSI, LSE, LSI, CSI)
* HSI at 64MHZ (HSIDIV = 1/1)
* HSE using a digital external clock at 24MHz
* LSE using an external crystal a 32.768kHz (the typical frequency)

We highlight the customized parts:
  / {
  	clocks {
  		clk_hse: clk-hse {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <{{Highlight|24000000}}>;
  			{{Highlight|st,digbypass;}}
  		};

  		clk_hsi: clk-hsi {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <{{Highlight|64000000}}>;
  		};

  		clk_lse: clk-lse {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <{{Highlight|32768}}>;
  		};

  		clk_lsi: clk-lsi {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <32000>;
  		};

  		clk_csi: clk-csi {
  			#clock-cells = <0>;
  			compatible = "fixed-clock";
  			clock-frequency = <4000000>;
  		};
  	};
  };

So the resulting board device tree, based on SoC device tree "stm32mp157c.dtsi", is :

  #include "stm32mp157c.dtsi"
  &clk_hse {
  	clock-frequency = <{{Highlight|24000000}}>;
  	{{Highlight|st,digbypass;}}
  };

  &clk_hsi {
  	clock-frequency = <{{Highlight|64000000}}>;
  };

  &clk_lse {
  	clock-frequency = <{{Highlight|32768}}>;
  };

It is the configuration used by TF-A for STM32MP157C-EV1 <ref name="stm32mp157c-ed1"/>


==== STM32MP1 clock node ====
Please refer to [[Clock device tree configuration|clock device tree configuration]] for information on how to specify the number of cells in a clock specifier.

The bootloader performs a global clock initialization, as described below. The information related to a given board can be found in the board specific device tree files listed in [[#clock_node|clock node]].

The bootloader uses other properties for [[RCC_internal_peripheral|RCC]] node ("st,stm32mp1-rcc" compatible):
* secure-status: related to TZEN bit configuration in RCC_TZCR register that allows to restrict RCC register and PWR registers write access
* st,clksrc: clock source configuration array
* st,clkdiv: clock divider configuration array
* st,pll: specific PLL configuration
* st,pkcs: peripheral kernel clock distribution configuration array.

All the available clocks are defined as preprocessor macros in ''stm32mp1-clks.h''<ref name="stm32mp1-clks">{{CodeSource | TF-A | include/dt-bindings/clock/stm32mp1-clks.h}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot | include/dt-bindings/clock/stm32mp1-clks.h}} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP1 DT bindings clock identifier files</ref> and can be used in device tree sources.

===== Defining clock source distribution with st,clksrc property =====
This property can be used to configure the clock distribution tree. When used, it must describe the whole distribution tree.

There are nine clock source selectors for the STM32MP15 devices. They must be configured in the following order: MPU, AXI, MCU, PLL12, PLL3, PLL4, RTC, MCO1, and MCO2.

The clock source configuration values are defined by the CLK_<NAME>_<SOURCE> macros located in ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc"></ref>.

Example:<pre>

        st,clksrc = <
                CLK_MPU_PLL1P
                CLK_AXI_PLL2P
                CLK_MCU_PLL3P
                CLK_PLL12_HSE
                CLK_PLL3_HSE
                CLK_PLL4_HSE
                CLK_RTC_LSE
                CLK_MCO1_DISABLED
                CLK_MCO2_DISABLED
        >;</pre>


===== Defining clock dividers with st,clkdiv property =====
This property can be used to configure the value of the clock main dividers. When used, it must describe the whole clock divider tree.

There are 11 dividers values for the STM32MP15 devices. They must be configured in the following order: MPU, AXI, MCU, APB1, APB2, APB3, APB4, APB5, RTC, MCO1 and MCO2.

Each divider value uses the DIV coding defined in the [[RCC_internal_peripheral|RCC]] associated register, RCC_xxxDIVR. In most cases, this value is the following:
* 0x0: not divided
* 0x1: division by 2
* 0x2: division by 4
* 0x3: division by 8
* ...

Note that the coding differs for RTC MCO1 and MCO2:
* 0x0: not divided
* 0x1: division by 2
* 0x2: division by 3
* 0x3: division by 4
* ...

Example:<pre>

        st,clkdiv = <
                1 /*MPU*/
                0 /*AXI*/
                0 /*MCU*/
                1 /*APB1*/
                1 /*APB2*/
                1 /*APB3*/
                1 /*APB4*/
                2 /*APB5*/
                23 /*RTC*/
                0 /*MCO1*/
                0 /*MCO2*/
        >;</pre>


===== Defining peripheral PLL frequencies with st,pll property =====
This property can be used to configure PLL frequencies.

PLL children nodes for PLL1 to PLL4 (see [[STM32MP15 resources|reference manual]] for details) are associated with an index from 0 to 3 (st,pll@0 to st,pll@3). PLLx is off when the associated node is absent.

Below the available properties for each PLL node:
* cfg contains the PLL configuration parameters in the following order: DIVM, DIVN, DIVP, DIVQ, DIVR, output.
:: DIVx values are defined as in [[RCC_internal_peripheral|RCC]]:
:::* 0x0: bypass (division by 1)
:::* 0x1: division by 2
:::* 0x2: division by 3
:::* 0x3: division by 4
:::* ...

:: Output contains a bitfield for each output value (1:ON / 0:OFF)
:::* BIT(0) → output P : DIVPEN
:::* BIT(1) → output Q : DIVQEN
:::* BIT(2) → output R : DIVREN
:::Note: PQR(p,q,r) macro can be used to build this value with p, q, r = 0 or 1.

* frac: fractional part of the multiplication factor (optional, when absent PLL is in integer mode).

* csg contains the clock spreading generator parameters (optional) in the following order: MOD_PER, INC_STEP and SSCG_MODE.
:: MOD_PER: modulation period adjustment
:: INC_STEP: modulation depth adjustment
:: SSCG_MODE: Spread spectrum clock generator mode, defined in ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc"></ref>:
:::* SSCG_MODE_CENTER_SPREAD = 0
:::* SSCG_MODE_DOWN_SPREAD = 1

Example:<pre>

	st,pll@0 {
		cfg = < 1 53 0 0 0 1 >;
		frac = < 0x810 >;
	};
	st,pll@1 {
		cfg = < 1 43 1 0 0 PQR(0,1,1) >;
		csg = < 10 20 1 >;
	};
	st,pll@2 {
		cfg = < 2 85 3 13 3 0 >;
		csg = < 10 20 SSCG_MODE_CENTER_SPREAD >;
	};
	st,pll@3 {
		cfg = < 2 78 4 7 9 3 >;
	};</pre>


===== Defining peripheral kernel clock tree distribution with st,pkcs property =====
This property can be used to configure the peripheral kernel clock selection.

It is a list of peripheral kernel clock source identifiers defined by the CLK_<KERNEL-CLOCK>_<PARENT-CLOCK> macros in the ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc"></ref> header file.

st,pkcs may not list all the kernel clocks. No specific order is required.

Example:<pre>

	st,pkcs = <
		CLK_STGEN_HSE
		CLK_CKPER_HSI
		CLK_USBPHY_PLL2P
		CLK_DSI_PLL2Q
                CLK_I2C46_HSI
                CLK_UART1_HSI
                CLK_UART24_HSI
	>;</pre>


===== HSI and CSI clockclocks calibration =====The [[How_to_activate_HSI_and_CSI_oscillators_calibration|Calibrationcalibration]] is an optional feature that can be enabled from the device tree. It
allows requesting the HSI or CSI clock calibration by several means:
* SiP SMC service
* Periodic calibration every X seconds
* Interrupt raised by the MCU

This feature requires that a hardware timer is assigned to the calibration sequence.

A dedicated interrupt must be defined using "mcu_sev" name to start a calibration on detection of an interrupt raised by the MCU.

* st,hsi-cal: used to enable HSI clock calibration feature.
* st,csi-cal; used to enable CSI clock calibration feature.
* st,cal-sec: used to enable periodic calibration at specified time intervals from the secure monitor. The time interval must be given in seconds. If not specified, a calibration is only processed for each incoming request.

Example:<pre>

	&rcc {
		st,hsi-cal;
		st,csi-cal;
		st,cal-sec = <15>;
		secure-interrupts = <GIC_SPI 144 IRQ_TYPE_LEVEL_HIGH>,<GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>;
		interrupt-names = "mcu_sev", "wakeup";
	};</pre>


==How to configure the DT using STM32CubeMX==
The [[STM32CubeMX]] tool can be used to configure the STM32MPU device and get the corresponding [[Device_tree#STM32|platform configuration device tree]] files.

The STM32CubeMX may not support all the properties described in the above [[#DT bindings documentation|DT bindings documentation]] paragraph. <br />If so, the tool inserts '''user sections''' in the generated device tree.<br /> These sections can then be edited to add some properties and they are preserved from one generation to another.

Refer to [[STM32CubeMX]] user manual for further information.

==References==
Please refer to the following links for additional information:
<references />

<noinclude>

{{ArticleBasedOnModel | Contributors:Peripheral or framework device tree configuration model}}
[[Category:Device tree configuration]]
[[Category:Trusted Firmware-A (TF-A)]]
[[Category:U-Boot]]</noinclude>
(40 intermediate revisions by 3 users not shown)
Line 1: Line 1:
<noinclude>
 
{{ArticleBasedOnModel | [[Contributors:Peripheral or framework device tree configuration model]]}}
 
{{ArticleMainWriter | NicolasLB}}
 
{{ArticleApprovedVersion | NicolasLB | LionelD, YannG, PatrickD, GeraldB | No previous approved version | AnneJ - 04Feb'19 - 10612 | 24 January'19}}
 
[[Category:Device tree configuration]]
 
[[Category:Trusted Firmware-A (TF-A)]]
 
[[Category:U-Boot]]
 
</noinclude>
 
 
 
 
== Article purpose ==
 
== Article purpose ==
   
This article describes the specific [[RCC internal peripheral|'''RCC''' internal peripheral]] configuration done by the [[Boot chains overview|first stage bootloader]].
+
This article describes the specific [[RCC internal peripheral|'''RCC''' internal peripheral]] configuration done by the [[Boot chains overview|first stage bootloader]]:
  +
* [[TF-A overview|TF-A]] for the Trusted boot chain
  +
* [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] for the Basic boot chain
   
 
{{Warning|This article explains how to configure the clock tree in the [[RCC_internal_peripheral|RCC]] at boot time.<br/>You can then refer to the [[Clock device tree configuration|clock device tree configuration]] article to understand how to derive each internal peripheral clock tree in Linux<sup>&reg;</sup> OS from the [[RCC_internal_peripheral|RCC]] clock tree.}}
 
{{Warning|This article explains how to configure the clock tree in the [[RCC_internal_peripheral|RCC]] at boot time.<br/>You can then refer to the [[Clock device tree configuration|clock device tree configuration]] article to understand how to derive each internal peripheral clock tree in Linux<sup>&reg;</sup> OS from the [[RCC_internal_peripheral|RCC]] clock tree.}}
   
 
The configuration is performed using the [[Device tree|device tree]] mechanism that provides a hardware description of the [[RCC_internal_peripheral|RCC]] peripheral.
 
The configuration is performed using the [[Device tree|device tree]] mechanism that provides a hardware description of the [[RCC_internal_peripheral|RCC]] peripheral.
  +
  +
This clock tree is only used in the device tree of the boot chain FSBL; so in the TF-A device tree for OpenSTLinux official delivery (or in SPL only for the DDR tuning tool).
  +
  +
Even if the clock tree information is also present in the [[U-Boot_overview|U-Boot]] device tree, it is not used during boot by this SSBL.
   
 
== DT bindings documentation ==
 
== DT bindings documentation ==
   
The bootloader clock device tree bindings are composed of the vendor clock DT bindings used by the clk-stm32mp1 [[TF-A overview|TF-A]] and by the [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] driver.
+
The bootloader clock device tree bindings correspond to the vendor clock DT bindings used by the clk-stm32mp1 driver of the FSBL ([[TF-A overview|TF-A]] or [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]), it is based on:
  +
*  binding described in [[Clock_device_tree_configuration]]
  +
*  bootloader specific properties described in [[#DT configuration]]
   
 
This binding document explains how to write device tree files for clocks on bootloader side:
 
This binding document explains how to write device tree files for clocks on bootloader side:
* [[TF-A overview|TF-A]]: ''<TF-A directory>/docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt''
+
* [[TF-A overview|TF-A]]: ''tf-a/docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt"<ref name="st,stm32mp1-rcc.txt"> {{CodeSource | TF-A | docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt}} [[TF-A overview|TF-A]] clock binding information file</ref>
 
* [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''doc/device-tree-bindings/clock/st,stm32mp1.txt''<ref name="st,stm32mp1.txt">{{CodeSource | U-Boot | doc/device-tree-bindings/clock/st,stm32mp1.txt}} [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] clock binding information file</ref>
 
* [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''doc/device-tree-bindings/clock/st,stm32mp1.txt''<ref name="st,stm32mp1.txt">{{CodeSource | U-Boot | doc/device-tree-bindings/clock/st,stm32mp1.txt}} [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] clock binding information file</ref>
 
{{Info|Please note that the upstreaming of this [[TF-A overview|TF-A]] file is in progress}}
 
   
 
== DT configuration ==
 
== DT configuration ==
Line 34: Line 30:
 
=== DT configuration (STM32 level) ===
 
=== DT configuration (STM32 level) ===
 
The STM32MP1 clock nodes are located in ''stm32mp157c.dtsi''<ref name="stm32mp157_pin_dtsi">{{CodeSource | TF-A | fdts/stm32mp157c.dtsi}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot| arch/arm/dts/stm32mp157c.dtsi }} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP157C device tree files</ref> (see [[Device tree]] for more explanations):
 
The STM32MP1 clock nodes are located in ''stm32mp157c.dtsi''<ref name="stm32mp157_pin_dtsi">{{CodeSource | TF-A | fdts/stm32mp157c.dtsi}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot| arch/arm/dts/stm32mp157c.dtsi }} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP157C device tree files</ref> (see [[Device tree]] for more explanations):
* fixed-clock define in [[#clock node|clock node]]
+
* fixed-clock defined in [[#clock node|clock node]]
* [[RCC_internal_peripheral|RCC]] node for [[#STM32MP1 Clock node]]: clock generation and distribution.
+
* [[RCC_internal_peripheral|RCC]] node for [[#STM32MP1 clock node]]: clock generation and distribution.
 
 
Please refer to [[Clock device tree configuration|clock device tree configuration]] for the bindings common with Linux<sup>&reg;</sup> kernel.
 
   
 
   / {
 
   / {
Line 65: Line 59:
 
    
 
    
 
   };
 
   };
  +
  +
Please refer to [[Clock device tree configuration|clock device tree configuration]] for the bindings common with Linux<sup>&reg;</sup> kernel.
   
 
=== DT configuration (board level) ===
 
=== DT configuration (board level) ===
Line 73: Line 69:
 
* clk-hsi
 
* clk-hsi
 
* clk-hse
 
* clk-hse
* clk-csi.
+
* clk-csi
 
Please refer to [[Clock device tree configuration|clock device tree configuration]] for detailed information.
 
Please refer to [[Clock device tree configuration|clock device tree configuration]] for detailed information.
   
 
At boot time, the clock tree initialization performs the following tasks:
 
At boot time, the clock tree initialization performs the following tasks:
* enabling of the oscillators present in the device tree,
+
* enabling of the oscillators present in the device tree and not disabled (node with status="disabled"),
* disabling of the HSI oscillator if the node is absent (always activated by bootROM).
+
* disabling of the HSI oscillator if the node is absent or disabled (HSI is always activated by the ROM code).
   
 
This information is located in the following files:
 
This information is located in the following files:
Line 84: Line 80:
 
** [[TF-A overview|TF-A]]: ''fdts/stm32mp157c-ed1.dts''<ref name="stm32mp157c-ed1">{{CodeSource | TF-A | fdts/stm32mp157c-ed1.dts}} STM32MP157C-ED1 device tree file for [[TF-A overview|TF-A]]</ref>
 
** [[TF-A overview|TF-A]]: ''fdts/stm32mp157c-ed1.dts''<ref name="stm32mp157c-ed1">{{CodeSource | TF-A | fdts/stm32mp157c-ed1.dts}} STM32MP157C-ED1 device tree file for [[TF-A overview|TF-A]]</ref>
 
** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi''<ref name="stm32mp157c-ed1-u-boot">{{CodeSource | U-Boot | arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi}} STM32MP157C-ED1 device tree file for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]</ref>
 
** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi''<ref name="stm32mp157c-ed1-u-boot">{{CodeSource | U-Boot | arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi}} STM32MP157C-ED1 device tree file for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]</ref>
* STM32MP157X-DK1 and STM32MP157X-DK2:  
+
* STM32MP157A-DK1 and STM32MP157C-DK2:  
** [[TF-A overview|TF-A]]: ''<TF-A directory>/fdts/stm32mp157a-dk1.dts''.
+
** [[TF-A overview|TF-A]]: ''fdts/stm32mp157a-dk1.dts''<ref name="stm32mp157c-dk1">{{CodeSource | TF-A | fdts/stm32mp157a-dk1.dts}} STM32MP157A-DK1 device tree file for [[TF-A overview|TF-A]]</ref>.
** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''< U-Boot directory>/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi''.
+
** [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]: ''arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi''<ref name="stm32mp157a-dk1-u-boot">{{CodeSource | U-Boot | arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi}} STM32MP157C-DK1 device tree file for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]</ref>.
{{Info|Please note that the upstreaming of these two [[TF-A overview|TF-A]] / [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]] files is in progress}}
 
   
 
Optional properties are described below.
 
Optional properties are described below.
   
 
===== Optional properties for "clk-lse" and "clk-hse" external oscillators =====
 
===== Optional properties for "clk-lse" and "clk-hse" external oscillators =====
  +
  +
For external oscillator HSE and LSE, the default clock configuration is an external crystal/ceramic resonator.
  +
 
Four optional fields are supported:
 
Four optional fields are supported:
* "st,bypass" configures the oscillator bypass mode (HSEBYP, LSEBYP),
+
* "st,bypass" configures the external analog clock source (set HSEBYP, LSEBYP),
* "st,digbypass" configures the bypass mode as full-swing digital signal (DIGBYP),
+
* "st,digbypass" configures the external digital clock source (set DIGBYP and HSEBYP, LSEBYP),
 
* "st,css" activates the clock security system (HSECSSON, LSECSSON),
 
* "st,css" activates the clock security system (HSECSSON, LSECSSON),
 
* "st,drive" (LSE only) contains the value of the drive for the oscillator (see LSEDRV_ defined in the file ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc">{{CodeSource | TF-A | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP1 DT bindings clock source files</ref>).
 
* "st,drive" (LSE only) contains the value of the drive for the oscillator (see LSEDRV_ defined in the file ''stm32mp1-clksrc.h''<ref name="stm32mp1-clksrc">{{CodeSource | TF-A | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[TF-A overview|TF-A]]), {{CodeSource | U-Boot | include/dt-bindings/clock/stm32mp1-clksrc.h}} (for [[U-Boot_overview#SPL:_FSBL_for_basic_boot|U-Boot SPL]]): STM32MP1 DT bindings clock source files</ref>).
   
Below an example of board file:
+
===== DT configuration for HSE =====
<pre>
+
 
/ {
+
The HSE can accept an external crystal/ceramic or external clock source on OSC_IN, digital or analog : the user needs to select the correct frequency and the correct configuration in the device tree, corresponding to the hardware setup.
clocks {
+
 
clk_hse: clk-hse {
+
All the ST boards are using a digital external clock configuration (so device tree with = st,digbypass).
#clock-cells = <0>;
+
 
compatible = "fixed-clock";
+
For example with the same 24MHz frequency, we have 3 configurations:
clock-frequency = <24000000>;
+
 
st,bypass;
+
[[File:Hse config.jpg|800px|none|]]
};
+
 
  +
* Digital external clock = st,digbypass
  +
  / {
  +
  clocks {
  +
  clk_hse: clk-hse {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|24000000}}>;
  +
  {{Highlight|st,digbypass;}}
  +
  };
  +
  };
  +
 
  +
* Analog external clock = st,bypass
  +
  / {
  +
  clocks {
  +
  clk_hse: clk-hse {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|24000000}}>;
  +
  {{Highlight|st,bypass;}}
  +
};
  +
  };
  +
 
  +
* Crystal/ ceramic resonators configuration
  +
  / {
  +
  clocks {
  +
  clk_hse: clk-hse {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|24000000}}>;
  +
  };
  +
  };
  +
 
  +
===== DT configuration for LSE =====
  +
 
  +
Below an example of LSE on board file with 32,768kHz crystal resonators, the drive set to medium high and with activated clock security system.
   
clk_lse: clk-lse {
+
  / {
#clock-cells = <0>;
+
  clocks {
compatible = "fixed-clock";
+
  clk_lse: clk-lse {
clock-frequency = <32768>;
+
  #clock-cells = <0>;
st,css;
+
  compatible = "fixed-clock";
st,drive = <LSEDRV_LOWEST>;
+
  clock-frequency = <{{Highlight|32768}}>;
};
+
  {{Highlight|st,css;}}
};
+
  st,drive = <{{Highlight|LSEDRV_MEDIUM_HIGH}}>;
</pre>
+
  };
  +
  };
   
 
===== Optional property for "clk-hsi" internal oscillator =====
 
===== Optional property for "clk-hsi" internal oscillator =====
Line 145: Line 179:
 
   };
 
   };
 
   };
 
   };
  +
  +
===== Clock node example =====
  +
  +
An example of clocks node with:
  +
* all oscillators switched on (HSE, HSI, LSE, LSI, CSI)
  +
* HSI at 64MHZ (HSIDIV = 1/1)
  +
* HSE using a digital external clock at 24MHz
  +
* LSE using an external crystal a 32.768kHz (the typical frequency)
  +
  +
We highlight the customized parts:
  +
  / {
  +
  clocks {
  +
  clk_hse: clk-hse {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|24000000}}>;
  +
  {{Highlight|st,digbypass;}}
  +
  };
  +
 
  +
  clk_hsi: clk-hsi {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|64000000}}>;
  +
  };
  +
 
  +
  clk_lse: clk-lse {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <{{Highlight|32768}}>;
  +
  };
  +
 
  +
  clk_lsi: clk-lsi {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <32000>;
  +
  };
  +
 
  +
  clk_csi: clk-csi {
  +
  #clock-cells = <0>;
  +
  compatible = "fixed-clock";
  +
  clock-frequency = <4000000>;
  +
  };
  +
  };
  +
  };
  +
  +
So the resulting board device tree, based on SoC device tree "stm32mp157c.dtsi", is :
  +
  +
  #include "stm32mp157c.dtsi"
  +
  &clk_hse {
  +
  clock-frequency = <{{Highlight|24000000}}>;
  +
  {{Highlight|st,digbypass;}}
  +
  };
  +
 
  +
  &clk_hsi {
  +
  clock-frequency = <{{Highlight|64000000}}>;
  +
  };
  +
 
  +
  &clk_lse {
  +
  clock-frequency = <{{Highlight|32768}}>;
  +
  };
  +
  +
It is the configuration used by TF-A for STM32MP157C-EV1 <ref name="stm32mp157c-ed1"/>
   
 
==== STM32MP1 clock node ====
 
==== STM32MP1 clock node ====
Line 151: Line 247:
 
The bootloader performs a global clock initialization, as described below. The information related to a given board can be found in the board specific device tree files listed in [[#clock_node|clock node]].
 
The bootloader performs a global clock initialization, as described below. The information related to a given board can be found in the board specific device tree files listed in [[#clock_node|clock node]].
   
The bootloader uses other properties:
+
The bootloader uses other properties for [[RCC_internal_peripheral|RCC]] node ("st,stm32mp1-rcc" compatible):
* secure-status: related to TZEN bit configuration in RCC_TZCR register that allows to restrict RCC register write access
+
* secure-status: related to TZEN bit configuration in RCC_TZCR register that allows to restrict RCC and PWR registers write access
 
* st,clksrc: clock source configuration array
 
* st,clksrc: clock source configuration array
 
* st,clkdiv: clock divider configuration array
 
* st,clkdiv: clock divider configuration array
Line 286: Line 382:
 
</pre>
 
</pre>
   
===== HSI and CSI clock calibration =====
+
===== HSI and CSI clocks calibration =====
[[How_to_activate_HSI_and_CSI_oscillators_calibration|Calibration]] is an optional feature that can be enabled from the device tree. It
+
The [[How_to_activate_HSI_and_CSI_oscillators_calibration|calibration]] is an optional feature that can be enabled from the device tree. It
 
allows requesting the HSI or CSI clock calibration by several means:
 
allows requesting the HSI or CSI clock calibration by several means:
 
* SiP SMC service
 
* SiP SMC service
Line 299: Line 395:
 
* st,hsi-cal: used to enable HSI clock calibration feature.
 
* st,hsi-cal: used to enable HSI clock calibration feature.
 
* st,csi-cal; used to enable CSI clock calibration feature.
 
* st,csi-cal; used to enable CSI clock calibration feature.
* st,cal-sec: used to enable periodic calibration at specified time intervals from the secure monitor. The time interval must be given in seconds. If not specified, a calibration is processed for each incoming request.
+
* st,cal-sec: used to enable periodic calibration at specified time intervals from the secure monitor. The time interval must be given in seconds. If not specified, a calibration is only processed for each incoming request.
   
 
Example:
 
Example:
Line 324: Line 420:
   
 
<references />
 
<references />
  +
  +
<noinclude>
  +
{{ArticleBasedOnModel | Contributors:Peripheral or framework device tree configuration model}}
  +
[[Category:Device tree configuration]]
  +
[[Category:Trusted Firmware-A (TF-A)]]
  +
[[Category:U-Boot]]
  +
</noinclude>

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