From mboxrd@z Thu Jan 1 00:00:00 1970 From: gabriel.fernandez@st.com (gabriel.fernandez at st.com) Date: Thu, 21 Jul 2016 11:19:26 +0200 Subject: [PATCH v2 2/4] dt-bindings: Document the STM32 reset bindings In-Reply-To: <1469092768-17489-1-git-send-email-gabriel.fernandez@st.com> References: <1469092768-17489-1-git-send-email-gabriel.fernandez@st.com> Message-ID: <1469092768-17489-3-git-send-email-gabriel.fernandez@st.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Maxime Coquelin This adds documentation of device tree bindings for the STM32 reset controller. Signed-off-by: Maxime Coquelin Signed-off-by: Gabriel Fernandez --- .../devicetree/bindings/clock/st,stm32-rcc.txt | 42 ++++++++++++++++++---- .../devicetree/bindings/reset/st,stm32-rcc.txt | 6 ++++ 2 files changed, 41 insertions(+), 7 deletions(-) create mode 100644 Documentation/devicetree/bindings/reset/st,stm32-rcc.txt diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt index fee3205..c209de6 100644 --- a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt +++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt @@ -1,16 +1,16 @@ STMicroelectronics STM32 Reset and Clock Controller =================================================== -The RCC IP is both a reset and a clock controller. This documentation only -describes the clock part. +The RCC IP is both a reset and a clock controller. -Please also refer to clock-bindings.txt in this directory for common clock -controller binding usage. +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" - 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 @@ -19,6 +19,7 @@ Required properties: Example: rcc: rcc at 40023800 { + #reset-cells = <1>; #clock-cells = <2> compatible = "st,stm32f42xx-rcc", "st,stm32-rcc"; reg = <0x40023800 0x400>; @@ -35,16 +36,23 @@ 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 0> + clocks = <&rcc 0 STM32F4_AHB1_CLOCK(GPIOA)> }; /* Gated clock, AHB2 bit 4 (CRYP) */ ... { - clocks = <&rcc 0 36> + clocks = <&rcc 0 STM32F4_AHB2_CLOCK(CRYP)> }; Specifying other clocks @@ -61,5 +69,25 @@ Example: /* Misc clock, FCLK */ ... { - clocks = <&rcc 1 1> + 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)>; }; diff --git a/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt new file mode 100644 index 0000000..01db343 --- /dev/null +++ b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt @@ -0,0 +1,6 @@ +STMicroelectronics STM32 Peripheral Reset Controller +==================================================== + +The RCC IP is both a reset and a clock controller. + +Please see Documentation/devicetree/bindings/clock/st,stm32-rcc.txt -- 1.9.1