1. Article purpose[edit | edit source]
The purpose of this article is to explain how to configure the RCC internal peripheral clocks using the device tree mechanism, relying on the bindings documentation, that is the description of the required and optional device-tree properties.
The peripheral can be assigned to different contexts/software components, depending on the final product needs. Refer to How to assign an internal peripheral to an execution context article for guidelines on this configuration .
2. DT bindings documentation[edit | edit source]
The device tree binding documents are stored either in the given applicable components listed below, or in the Linux kernel repository:
- TF-A BL2:
- for STM32MP13x lines
docs/devicetree/bindings/clock/st,stm32mp13-rcc.txt - for STM32MP15x lines docs/devicetree/bindings/clock/st,stm32mp1-rcc.txt
- for STM32MP13x lines
- OP-TEE:
- for STM32MP13x lines documentation/devicetree/bindings/clock/st,stm32mp13-rcc.yaml
- for STM32MP15x lines documentation/devicetree/bindings/clock/st,stm32mp1-rcc.yaml
- for STM32MP13x lines
- U-Boot, Linux® OS:
- for STM32MP1 Series Documentation/devicetree/bindings/clock/st,stm32mp1-rcc.yaml
3. DT configuration[edit | edit source]
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 organization.
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/SoC level)[edit | edit source]
The RCC node is located in the device tree file for the software components, supporting the peripheral and listed in the above DT bindings documentation paragraph.
3.2. DT configuration (board level)[edit | edit source]
The objective of this chapter is to explain how to configure a clock tree related to the board.
Using this chapter, the end-user can configure any
parameters via the DT to adapt to a new board.
3.2.1. STM32MP15x lines [edit | edit source]
Clock tree configuration it's done in TF-A and in OP-TEE.
Usually a minimal configuration is applied in TF-A BL2 and the full configuration in OP-TEE.
This an example a clock configuration tree:
&rcc {
st,clksrc = <
CLK_MPU_PLL1P
CLK_AXI_PLL2P
CLK_MCU_PLL3P
CLK_RTC_LSE
CLK_MCO1_DISABLED
CLK_MCO2_DISABLED
CLK_CKPER_HSE
CLK_FMC_ACLK
CLK_QSPI_ACLK
CLK_ETH_PLL4P
CLK_SDMMC12_PLL4P
CLK_DSI_DSIPLL
CLK_STGEN_HSE
CLK_USBPHY_HSE
CLK_SPI2S1_PLL3Q
CLK_SPI2S23_PLL3Q
CLK_SPI45_HSI
CLK_SPI6_HSI
CLK_I2C46_HSI
CLK_SDMMC3_PLL4P
CLK_USBO_USBPHY
CLK_ADC_CKPER
CLK_CEC_LSE
CLK_I2C12_HSI
CLK_I2C35_HSI
CLK_UART1_HSI
CLK_UART24_HSI
CLK_UART35_HSI
CLK_UART6_HSI
CLK_UART78_HSI
CLK_SPDIF_PLL4P
CLK_FDCAN_PLL4R
CLK_SAI1_PLL3Q
CLK_SAI2_PLL3Q
CLK_SAI3_PLL3Q
CLK_SAI4_PLL3Q
CLK_RNG1_CSI
CLK_RNG2_LSI
CLK_LPTIM1_PCLK1
CLK_LPTIM23_PCLK3
CLK_LPTIM45_LSE
>;
st,clkdiv = <
DIV(DIV_MPU, 1)
DIV(DIV_AXI, 0)
DIV(DIV_MCU, 0)
DIV(DIV_APB1, 1)
DIV(DIV_APB2, 1)
DIV(DIV_APB3, 1)
DIV(DIV_APB4, 1)
DIV(DIV_APB5, 2)
DIV(DIV_RTC, 23)
DIV(DIV_MCO1, 0)
DIV(DIV_MCO2, 0)
>;
st,pll_vco {
pll2_vco_1066Mhz: pll2-vco-1066Mhz {
src = <CLK_PLL12_HSE>;
divmn = <2 65>;
frac = <0x1400>;
};
pll3_vco_417Mhz: pll3-vco-417Mhz {
src = <CLK_PLL3_HSE>;
divmn = <1 33>;
frac = <0x1a04>;
};
pll4_vco_594Mhz: pll4-vco-594Mhz {
src = <CLK_PLL4_HSE>;
divmn = <3 98>;
};
};
/* VCO = 1066.0 MHz => P = 266 (AXI), Q = 533 (GPU), R = 533 (DDR) */
pll2: st,pll@1 {
compatible = "st,stm32mp1-pll";
reg = <1>;
st,pll = <&pll2_cfg1>;
pll2_cfg1: pll2_cfg1 {
st,pll_vco = <&pll2_vco_1066Mhz>;
st,pll_div_pqr = <1 0 0>;
};
};
/* VCO = 417.8 MHz => P = 209, Q = 24, R = 11 */
pll3: st,pll@2 {
compatible = "st,stm32mp1-pll";
reg = <2>;
st,pll = <&pll3_cfg1>;
pll3_cfg1: pll3_cfg1 {
st,pll_vco = <&pll3_vco_417Mhz>;
st,pll_div_pqr = <1 16 36>;
};
};
/* VCO = 594.0 MHz => P = 99, Q = 74, R = 74 */
pll4: st,pll@3 {
compatible = "st,stm32mp1-pll";
reg = <3>;
st,pll = <&pll4_cfg1>;
pll4_cfg1: pll4_cfg1 {
st,pll_vco = <&pll4_vco_594Mhz>;
st,pll_div_pqr = <5 7 7>;
};
};
You can find a full example of the board configuration here :
- in T-FA : fdts/stm32mp157c-ed1.dts
- in OP-TEE : core/arch/arm/dts/stm32mp157c-ed1.dts
3.2.2. STM32MP13x lines [edit | edit source]
Clock tree configuration it's done in TF-A and in OP-TEE.
Usually a minimal configuration is applied in TF-A BL2 and the full configuration in OP-TEE.
This an example a clock configuration tree:
&rcc {
st,clksrc = <
CLK_MPU_PLL1P
CLK_AXI_PLL2P
CLK_MLAHBS_PLL3
CLK_RTC_LSE
CLK_MCO1_HSE
CLK_MCO2_DISABLED
CLK_CKPER_HSE
CLK_ETH1_PLL4P
CLK_ETH2_PLL4P
CLK_SDMMC1_PLL4P
CLK_SDMMC2_PLL4P
CLK_STGEN_HSE
CLK_USBPHY_HSE
CLK_I2C4_HSI
CLK_I2C5_HSI
CLK_USBO_USBPHY
CLK_ADC2_CKPER
CLK_I2C12_HSI
CLK_UART1_HSI
CLK_UART2_HSI
CLK_UART35_HSI
CLK_UART4_HSI
CLK_UART6_HSI
CLK_UART78_HSI
CLK_SAES_AXI
CLK_DCMIPP_PLL2Q
CLK_LPTIM3_PCLK3
CLK_RNG1_PLL4R
>;
st,clkdiv = <
DIV(DIV_MPU, 1)
DIV(DIV_AXI, 0)
DIV(DIV_MLAHB, 0)
DIV(DIV_APB1, 1)
DIV(DIV_APB2, 1)
DIV(DIV_APB3, 1)
DIV(DIV_APB4, 1)
DIV(DIV_APB5, 2)
DIV(DIV_APB6, 1)
DIV(DIV_RTC, 0)
DIV(DIV_MCO1, 0)
DIV(DIV_MCO2, 0)
>;
st,pll_vco {
pll1_vco_2000Mhz: pll1-vco-2000Mhz {
src = <CLK_PLL12_HSE>;
divmn = <1 82>;
frac = <0xAAA>;
};
pll1_vco_1300Mhz: pll1-vco-1300Mhz {
src = <CLK_PLL12_HSE>;
divmn = <2 80>;
frac = <0x800>;
};
pll2_vco_1066Mhz: pll2-vco-1066Mhz {
src = <CLK_PLL12_HSE>;
divmn = <2 65>;
frac = <0x1400>;
};
pll3_vco_417Mhz: pll3-vco-417Mhz {
src = <CLK_PLL3_HSE>;
divmn = <1 33>;
frac = <0x1a04>;
};
pll4_vco_600Mhz: pll4-vco-600Mhz {
src = <CLK_PLL4_HSE>;
divmn = <1 49>;
};
};
/* VCO = 1300.0 MHz => P = 650 (CPU) */
pll1: st,pll@0 {
compatible = "st,stm32mp1-pll";
reg = <0>;
st,pll = <&pll1_cfg1>;
pll1_cfg1: pll1_cfg1 {
st,pll_vco = <&pll1_vco_1300Mhz>;
st,pll_div_pqr = <0 1 1>;
};
pll1_cfg2: pll1_cfg2 {
st,pll_vco = <&pll1_vco_2000Mhz>;
st,pll_div_pqr = <0 1 1>;
};
};
/* VCO = 1066.0 MHz => P = 266 (AXI), Q = 266, R = 533 (DDR) */
pll2: st,pll@1 {
compatible = "st,stm32mp1-pll";
reg = <1>;
st,pll = <&pll2_cfg1>;
pll2_cfg1: pll2_cfg1 {
st,pll_vco = <&pll2_vco_1066Mhz>;
st,pll_div_pqr = <1 1 0>;
};
};
/* VCO = 417.8 MHz => P = 209, Q = 24, R = 11 */
pll3: st,pll@2 {
compatible = "st,stm32mp1-pll";
reg = <2>;
st,pll = <&pll3_cfg1>;
pll3_cfg1: pll3_cfg1 {
st,pll_vco = <&pll3_vco_417Mhz>;
st,pll_div_pqr = <1 16 36>;
};
};
/* VCO = 600.0 MHz => P = 50, Q = 10, R = 50 */
pll4: st,pll@3 {
compatible = "st,stm32mp1-pll";
reg = <3>;
st,pll = <&pll4_cfg1>;
pll4_cfg1: pll4_cfg1 {
st,pll_vco = <&pll4_vco_600Mhz>;
st,pll_div_pqr = <11 59 11>;
};
};
};
You can find a full example of the board configuration here :
- in TF-A fdts/stm32mp135f-dk.dts
- in OP-TEE core/arch/arm/dts/stm32mp135f-dk.dts
4. How to configure the DT using STM32CubeMX[edit | edit source]
The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
STM32CubeMX may not support all the properties described in DT binding files listed 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 | edit source]
Please refer to the following links for additional information:
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