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This driver implements basic clock setup, only clock gating is implemented. This driver doesn't implement .of_match as it's binded by MFD RCC driver. Files include/dt-bindings/clock/stm32h7-clks.h and doc/device-tree-bindings/clock/st,stm32h7-rcc.txt will be available soon in a kernel tag, as all the bindings have been acked by Rob Herring [1]. [1] http://lkml.iu.edu/hypermail/linux/kernel/1704.0/00935.html Signed-off-by: Patrice Chotard <patrice.chotard@st.com> Reviewed-by: Simon Glass <sjg@chromium.org>
152 lines
4 KiB
Text
152 lines
4 KiB
Text
STMicroelectronics STM32H7 Reset and Clock Controller
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=====================================================
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The RCC IP is both a reset and a clock controller.
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Please refer to clock-bindings.txt for common clock controller binding usage.
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Please also refer to reset.txt for common reset controller binding usage.
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Required properties:
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- compatible: Should be:
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"st,stm32h743-rcc"
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- reg: should be register base and length as documented in the
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datasheet
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- #reset-cells: 1, see below
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- #clock-cells : from common clock binding; shall be set to 1
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- clocks: External oscillator clock phandle
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- high speed external clock signal (HSE)
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- low speed external clock signal (LSE)
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- external I2S clock (I2S_CKIN)
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- st,syscfg: phandle for pwrcfg, mandatory to disable/enable backup domain
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write protection (RTC clock).
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- pll x node: Allow to register a pll with specific parameters.
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Please see PLL section below.
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Example:
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rcc: rcc@58024400 {
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#reset-cells = <1>;
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#clock-cells = <2>
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compatible = "st,stm32h743-rcc", "st,stm32-rcc";
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reg = <0x58024400 0x400>;
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clocks = <&clk_hse>, <&clk_lse>, <&clk_i2s_ckin>;
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st,syscfg = <&pwrcfg>;
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#address-cells = <1>;
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#size-cells = <0>;
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vco1@58024430 {
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#clock-cells = <0>;
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compatible = "stm32,pll";
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reg = <0>;
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};
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vco2@58024438 {
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#clock-cells = <0>;
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compatible = "stm32,pll";
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reg = <1>;
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st,clock-div = <2>;
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st,clock-mult = <40>;
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st,frac-status = <0>;
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st,frac = <0>;
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st,vcosel = <1>;
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st,pllrge = <2>;
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};
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};
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STM32H7 PLL
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-----------
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The VCO of STM32 PLL could be reprensented like this:
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Vref --------- --------
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---->| / DIVM |---->| x DIVN | ------> VCO
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--------- --------
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^
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-------
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| FRACN |
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-------
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When the PLL is configured in integer mode:
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- VCO = ( Vref / DIVM ) * DIVN
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When the PLL is configured in fractional mode:
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- VCO = ( Vref / DIVM ) * ( DIVN + FRACN / 2^13)
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Required properties for pll node:
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- compatible: Should be:
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"stm32,pll"
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- #clock-cells: from common clock binding; shall be set to 0
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- reg: Should be the pll number.
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Optional properties:
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- st,clock-div: DIVM division factor : <1..63>
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- st,clock-mult: DIVN multiplication factor : <4..512>
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- st,frac-status:
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- 0 Pll is configured in integer mode
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- 1 Pll is configure in fractional mode
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- st,frac: Fractional part of the multiplication factor : <0..8191>
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- st,vcosel: VCO selection
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- 0: Wide VCO range:192 to 836 MHz
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- 1: Medium VCO range:150 to 420 MHz
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- st,pllrge: PLL input frequency range
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- 0: The PLL input (Vref / DIVM) clock range frequency is between 1 and 2 MHz
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- 1: The PLL input (Vref / DIVM) clock range frequency is between 2 and 4 MHz
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- 2: The PLL input (Vref / DIVM) clock range frequency is between 4 and 8 MHz
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- 3: The PLL input (Vref / DIVM) clock range frequency is between 8 and 16 MHz
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The peripheral clock consumer should specify the desired clock by
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having the clock ID in its "clocks" phandle cell.
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All available clocks are defined as preprocessor macros in
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dt-bindings/clock/stm32h7-clks.h header and can be used in device
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tree sources.
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Example:
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timer5: timer@40000c00 {
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compatible = "st,stm32-timer";
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reg = <0x40000c00 0x400>;
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interrupts = <50>;
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clocks = <&rcc TIM5_CK>;
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};
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Specifying softreset control of devices
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=======================================
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Device nodes should specify the reset channel required in their "resets"
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property, containing a phandle to the reset device node and an index specifying
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which channel to use.
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The index is the bit number within the RCC registers bank, starting from RCC
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base address.
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It is calculated as: index = register_offset / 4 * 32 + bit_offset.
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Where bit_offset is the bit offset within the register.
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For example, for CRC reset:
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crc = AHB4RSTR_offset / 4 * 32 + CRCRST_bit_offset = 0x88 / 4 * 32 + 19 = 1107
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All available preprocessor macros for reset are defined dt-bindings//mfd/stm32h7-rcc.h
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header and can be used in device tree sources.
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example:
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timer2 {
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resets = <&rcc STM32H7_APB1L_RESET(TIM2)>;
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};
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