Difference between revisions of "RTC device tree configuration"

[unchecked revision] [quality revision]
(DT bindings documentation)
(DT configuration)

1 Article purpose[edit]

The purpose of this article is to explain how to configure the RTC internal peripheral when it is assigned to the Linux® OS. In that case, it is controlled by the RTC framework.

The configuration is performed using the device tree mechanism that provides a hardware description of the RTC peripheral, used by the STM32 RTC Linux driver.

2 DT bindings documentation[edit]

The RTC is represented by the STM32 RTC device tree bindings[1]

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 explanations on an explanation of the device tree file split.

The 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 RTC node is declared in stm32mp157c.dtsi[2]. It describes the hardware register address, clocks and interrupts.

rtc: rtc@5c004000 {
	compatible = "st,stm32mp1-rtc";
	reg = <0x5c004000 0x400>;                               --> Register location and length
	clocks = <&rcc RTCAPB>, <&rcc RTC>;
	clock-names = "pclk", "rtc_ck";
	interrupts-extended = <GIC<&intc GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>,
			      <&exti 19 1>;
	status = "disabled";
};
Warning white.png Warning
This device tree part is related to STM32 microprocessors. It should be kept as is, without being modified by the end-user.

3.2 DT configuration (board level)[edit]

The objective of this chapter is to explain how to configure the DT nodes related to the STM32 board.
Thanks to this chapter, the end-user must be able to configure any parameters via the DT to adapt to a new board.
The below warning can be addedThis part is used to enable the RTC used on a board which is done by setting the status property to okay.

A st,lsco property is available to select and enable the RTC ouput on which RTC Low-Speed Clock is Output. The valid ouput values are defined here [3]. A pinctrl state named "default" may be defined to reserve pin for RTC output.

3.3 DT configuration examples[edit]

This chapter must provide an example of how to configure the DT to adapt it to a new board.
#include <dt-bindings/rtc/rtc-stm32.h>
...
&rtc {
	st,lsco = <RTC_OUT2_RMP>;
	pinctrl-0 = <&rtc_out2_rmp_pins_a>;
	pinctrl-names = "default";
};

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:


== Article purpose ==
The purpose of this article is to explain how to configure the [[RTC internal peripheral|'''RTC''' internal peripheral]] when it is assigned to the Linux<sup>&reg;</sup> OS. In that case, it is controlled by the [[RTC overview|RTC framework]]. 

The configuration is performed using the [[Device tree|device tree]] mechanism that provides a hardware description of the RTC peripheral, used by the STM32 RTC Linux driver.

== DT bindings documentation ==

The [[RTC internal peripheral|'''RTC''']] is represented by the ''STM32 RTC device tree bindings''<ref>{{CodeSource | Linux kernel | Documentation/devicetree/bindings/rtc/st,stm32-rtc.txt | Device tree bindings}}</ref>


== DT configuration ==
This hardware description is a combination of the '''STM32 microprocessor and board device tree files. See [[Device tree]] for explanations on ''' 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.
The '''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 '''RTC''' node is declared in stm32mp157c.dtsi<ref>{{CodeSource|Linux kernel|arch/arm/boot/dts/stm32mp157c.dtsi|STM32MP157C device tree}}</ref>. It describes the hardware register address, clocks and interrupts.

 rtc: rtc@5c004000 {
 	compatible = "st,stm32mp1-rtc";
 	reg = <0x5c004000 0x400>;                               {{highlight|--> Register location and length}}
 	clocks = <&rcc RTCAPB>, <&rcc RTC>;
 	clock-names = "pclk", "rtc_ck";
 	interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>-extended = <&intc GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>,<&exti 19 1>;
 	status = "disabled";
 };
{{Warning|This device tree part is related to STM32 microprocessors. It should be kept as is, without being modified by the end-user.}}

=== DT configuration (board level) ==={{Green|The objective of this chapter is to explain how to configure the DT nodes related to the STM32 board. <br> Thanks to this chapter, the end-user must be able to configure any parameters via the DT to adapt to a new board.<br> The below warning can be added. ''}}

=== DT configuration examples ===
{{Green|''This chapter must provide an example of how to configure the DT to adapt it to a new board. '' }}This part is used to enable the '''RTC''' used on a board which is done by setting the '''status''' property to '''okay'''.

A st,lsco property is available to select and enable the RTC ouput on which RTC Low-Speed Clock is Output. The valid ouput values are defined here <ref>{{CodeSource|Linux kernel|include/dt-bindings/rtc/rtc-stm32.h|STM32 RTC bindings constants}}</ref>. A pinctrl state named "default" may be defined to reserve pin for RTC output.

=== DT configuration examples ===
 #include <dt-bindings/rtc/rtc-stm32.h>

 ...
 &rtc {
 	st,lsco = <RTC_OUT2_RMP>;
 	pinctrl-0 = <&rtc_out2_rmp_pins_a>;
 	pinctrl-names = "default";
 };


==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.<br />

The STM32CubeMX may not support all the properties described in the above [[#DT bindings documentation|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.

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

<noinclude>

[[Category:Device tree configuration]]
[[Category:RTC|1]]
{{ArticleBasedOnModel|Peripheral or framework device tree configuration model}}</noinclude>
Line 9: Line 9:
   
 
== DT configuration ==
 
== 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.
   
This hardware description is a combination of STM32 microprocessor and board device tree files. See [[Device tree]] for explanations on 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.
 
 
The '''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) ===
 
===DT configuration (STM32 level) ===
Line 22: Line 21:
 
  clocks = <&rcc RTCAPB>, <&rcc RTC>;
 
  clocks = <&rcc RTCAPB>, <&rcc RTC>;
 
  clock-names = "pclk", "rtc_ck";
 
  clock-names = "pclk", "rtc_ck";
  interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
+
  interrupts-extended = <&intc GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>,
  +
      <&exti 19 1>;
 
  status = "disabled";
 
  status = "disabled";
 
  };
 
  };
Line 28: Line 28:
   
 
=== DT configuration (board level) ===
 
=== DT configuration (board level) ===
{{Green|The objective of this chapter is to explain how to configure the DT nodes related to the STM32 board. <br> Thanks to this chapter, the end-user must be able to configure any parameters via the DT to adapt to a new board.<br> The below warning can be added. ''}}
+
This part is used to enable the '''RTC''' used on a board which is done by setting the '''status''' property to '''okay'''.
  +
 
  +
A st,lsco property is available to select and enable the RTC ouput on which RTC Low-Speed Clock is Output. The valid ouput values are defined here <ref>{{CodeSource|Linux kernel|include/dt-bindings/rtc/rtc-stm32.h|STM32 RTC bindings constants}}</ref>. A pinctrl state named "default" may be defined to reserve pin for RTC output.
   
 
=== DT configuration examples ===
 
=== DT configuration examples ===
{{Green|''This chapter must provide an example of how to configure the DT to adapt it to a new board. '' }}
+
#include <dt-bindings/rtc/rtc-stm32.h>
  +
...
  +
&rtc {
  +
st,lsco = <RTC_OUT2_RMP>;
  +
pinctrl-0 = <&rtc_out2_rmp_pins_a>;
  +
pinctrl-names = "default";
  +
};
   
 
==How to configure the DT using STM32CubeMX==
 
==How to configure the DT using STM32CubeMX==