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Diffstat (limited to 'Documentation/devicetree/bindings/clock/st,stm32-rcc.txt')
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1 files changed, 138 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt new file mode 100644 index 0000000000..cfa04b614d --- /dev/null +++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt @@ -0,0 +1,138 @@ +STMicroelectronics STM32 Reset and Clock Controller +=================================================== + +The RCC IP is both a reset and a clock controller. + +Please refer to clock-bindings.txt for common clock controller binding usage. +Please also refer to reset.txt for common reset controller binding usage. + +Required properties: +- compatible: Should be: + "st,stm32f42xx-rcc" + "st,stm32f469-rcc" + "st,stm32f746-rcc" + "st,stm32f769-rcc" + +- reg: should be register base and length as documented in the + datasheet +- #reset-cells: 1, see below +- #clock-cells: 2, device nodes should specify the clock in their "clocks" + property, containing a phandle to the clock device node, an index selecting + between gated clocks and other clocks and an index specifying the clock to + use. +- clocks: External oscillator clock phandle + - high speed external clock signal (HSE) + - external I2S clock (I2S_CKIN) + +Example: + + rcc: rcc@40023800 { + #reset-cells = <1>; + #clock-cells = <2> + compatible = "st,stm32f42xx-rcc", "st,stm32-rcc"; + reg = <0x40023800 0x400>; + clocks = <&clk_hse>, <&clk_i2s_ckin>; + }; + +Specifying gated clocks +======================= + +The primary index must be set to 0. + +The secondary index is the bit number within the RCC register bank, starting +from the first RCC clock enable register (RCC_AHB1ENR, address offset 0x30). + +It is calculated as: index = register_offset / 4 * 32 + bit_offset. +Where bit_offset is the bit offset within the register (LSB is 0, MSB is 31). + +To simplify the usage and to share bit definition with the reset and clock +drivers of the RCC IP, macros are available to generate the index in +human-readble format. + +For STM32F4 series, the macro are available here: + - include/dt-bindings/mfd/stm32f4-rcc.h + +Example: + + /* Gated clock, AHB1 bit 0 (GPIOA) */ + ... { + clocks = <&rcc 0 STM32F4_AHB1_CLOCK(GPIOA)> + }; + + /* Gated clock, AHB2 bit 4 (CRYP) */ + ... { + clocks = <&rcc 0 STM32F4_AHB2_CLOCK(CRYP)> + }; + +Specifying other clocks +======================= + +The primary index must be set to 1. + +The secondary index is bound with the following magic numbers: + + 0 SYSTICK + 1 FCLK + 2 CLK_LSI (low-power clock source) + 3 CLK_LSE (generated from a 32.768 kHz low-speed external + crystal or ceramic resonator) + 4 CLK_HSE_RTC (HSE division factor for RTC clock) + 5 CLK_RTC (real-time clock) + 6 PLL_VCO_I2S (vco frequency of I2S pll) + 7 PLL_VCO_SAI (vco frequency of SAI pll) + 8 CLK_LCD (LCD-TFT) + 9 CLK_I2S (I2S clocks) + 10 CLK_SAI1 (audio clocks) + 11 CLK_SAI2 + 12 CLK_I2SQ_PDIV (post divisor of pll i2s q divisor) + 13 CLK_SAIQ_PDIV (post divisor of pll sai q divisor) + + 14 CLK_HSI (Internal ocscillator clock) + 15 CLK_SYSCLK (System Clock) + 16 CLK_HDMI_CEC (HDMI-CEC clock) + 17 CLK_SPDIF (SPDIF-Rx clock) + 18 CLK_USART1 (U(s)arts clocks) + 19 CLK_USART2 + 20 CLK_USART3 + 21 CLK_UART4 + 22 CLK_UART5 + 23 CLK_USART6 + 24 CLK_UART7 + 25 CLK_UART8 + 26 CLK_I2C1 (I2S clocks) + 27 CLK_I2C2 + 28 CLK_I2C3 + 29 CLK_I2C4 + 30 CLK_LPTIMER (LPTimer1 clock) + 31 CLK_PLL_SRC + 32 CLK_DFSDM1 + 33 CLK_ADFSDM1 + 34 CLK_F769_DSI +) + +Example: + + /* Misc clock, FCLK */ + ... { + clocks = <&rcc 1 STM32F4_APB1_CLOCK(TIM2)> + }; + + +Specifying softreset control of devices +======================================= + +Device nodes should specify the reset channel required in their "resets" +property, containing a phandle to the reset device node and an index specifying +which channel to use. +The index is the bit number within the RCC registers bank, starting from RCC +base address. +It is calculated as: index = register_offset / 4 * 32 + bit_offset. +Where bit_offset is the bit offset within the register. +For example, for CRC reset: + crc = AHB1RSTR_offset / 4 * 32 + CRCRST_bit_offset = 0x10 / 4 * 32 + 12 = 140 + +example: + + timer2 { + resets = <&rcc STM32F4_APB1_RESET(TIM2)>; + }; |