deleted>Frq07381 No edit summary |
imported>Bruno ballarin |
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{{ArticleBasedOnModel | [[Peripheral or framework device tree configuration model]]}} | {{ArticleBasedOnModel | [[Peripheral or framework device tree configuration model]]}} | ||
{{ArticleMainWriter | OlivierB}} | {{ArticleMainWriter | OlivierB}} | ||
{{ArticleApprovedVersion| GabrielF | OlivierB | No previous approved version | BrunoB - 21Jan-19 - 10339 | | {{ArticleApprovedVersion| GabrielF | OlivierB | No previous approved version | BrunoB - 21Jan-19 - 10339 | 06Feb'19}} | ||
[[Category:Device tree configuration]] | [[Category:Device tree configuration]] | ||
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== DT bindings documentation == | == DT bindings documentation == | ||
The | The RCC is a multifunction device. | ||
Each function is represented by a separate binding document: | |||
*generic DT bindings<ref>{{CodeSource | Linux kernel | Documentation/devicetree/bindings/clock/clock-bindings.txt | Documentation/devicetree/bindings/clock/clock-bindings.txt}}, Clock device tree bindings</ref> used by the Common Clock framework. | *generic DT bindings<ref>{{CodeSource | Linux kernel | Documentation/devicetree/bindings/clock/clock-bindings.txt | Documentation/devicetree/bindings/clock/clock-bindings.txt}}, Clock device tree bindings</ref> used by the Common Clock framework. | ||
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==== clocks node ==== | ==== clocks node ==== | ||
These clocks have a fixed frequency (generally | These clocks have a fixed frequency (generally they are oscillators) | ||
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==== STM32MP1 Clock node ==== | ==== STM32MP1 Clock node ==== | ||
We need to specify the number of | We need to specify the number of cells in a clock specifier. <br/> | ||
For the STM32MP1 this number shoud be 1 and is configured via 'clock-cells' property in rcc node. | For the STM32MP1 this number shoud be 1 and is configured via 'clock-cells' property in rcc node. | ||
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=== DT configuration (board level) === | === DT configuration (board level) === | ||
If a Linux driver | If a Linux driver needs a clock, it has to be added in its DT node:<br/> | ||
clocks = <phandle> : List of phandle and clock specifier pairs, one pair | clocks = <phandle> : List of phandle and clock specifier pairs, one pair | ||
:::::for each clock input to the device. Note: if the | :::::for each clock input to the device. Note: if the | ||
Revision as of 14:06, 6 February 2019
Template:ArticleBasedOnModel Template:ArticleMainWriter Template:ArticleApprovedVersion
1. Article purpose[edit source]
This article explains how to configure the RCC internal peripheral when it is assigned to the Linux® OS. In that case, it is controlled by the Common Clock framework.
The configuration is performed using the device tree mechanism that provides a hardware description of the RCC peripheral, used by the clk-stm32mp1 Linux driver and by the Common Clock framework.
2. DT bindings documentation[edit source]
The RCC is a multifunction device.
Each function is represented by a separate binding document:
- generic DT bindings[1] used by the Common Clock framework.
- vendor clock DT bindings[2] used by the clk-stm32mp1 driver: this binding document explains how to write device tree files for clocks.
3. DT configuration[edit source]
3.1. DT configuration (STM32 level)[edit source]
The STM32MP1 Clock node is located in the stm32mp157c.dtsi[3]. See Device tree for more explanations.
3.1.1. clocks node[edit source]
These clocks have a fixed frequency (generally they are oscillators)
clocks {
clk_hse: clk-hse {
#clock-cells = <0>;
compatible = "fixed-clock";
clock-frequency = <24000000>;
};
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>;
};
...
};
3.1.2. STM32MP1 Clock node[edit source]
We need to specify the number of cells in a clock specifier.
For the STM32MP1 this number shoud be 1 and is configured via 'clock-cells' property in rcc node.
rcc: rcc@50000000 {
compatible = "st,stm32mp1-rcc", "syscon";
#clock-cells = <1>;
#reset-cells = <1>;
reg = <0x50000000 0x1000>;
...
};
3.2. DT configuration (board level)[edit source]
If a Linux driver needs a clock, it has to be added in its DT node:
clocks = <phandle> : List of phandle and clock specifier pairs, one pair
- for each clock input to the device. Note: if the
- clock provider specifies '0' for #clock-cells, then
- only the phandle portion of the pair will appear.
- Example:
usart3: serial@4000f000 { compatible = "st,stm32h7-usart"; reg = <0x4000f000 0x400>; interrupt-names = "event", "wakeup"; interrupts-extended = <&intc GIC_SPI 39 IRQ_TYPE_LEVEL_HIGH>, <&exti 28 1>; clocks = <&rcc USART3_K>; wakeup-source; power-domains = <&pd_core>; status = "disabled"; };
4. How to configure the DT using STM32CubeMX[edit source]
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 source]
Please refer to the following links for additional information:
- ↑ Template:CodeSource, Clock device tree bindings
- ↑ Template:CodeSource, STM32MP1 clock device tree bindings
- ↑ Template:CodeSource STM32MP157C device tree file