--- /dev/null
+STMicroelectronics STM32MP1 clock tree initialization
+=====================================================
+
+The STM32MP clock tree initialization is based on device tree information
+for RCC IP and on fixed clocks.
+
+-------------------------------
+RCC CLOCK = st,stm32mp1-rcc-clk
+-------------------------------
+
+The RCC IP is both a reset and a clock controller but this documentation only
+describes the fields added for clock tree initialization which are not present
+in Linux binding.
+
+Please refer to ../mfd/st,stm32-rcc.txt for all the other properties common
+with Linux.
+
+Required properties:
+
+- compatible: Should be "st,stm32mp1-rcc-clk"
+
+- st,clksrc : The clock source in this order
+
+ for STM32MP15x: 9 clock sources are requested
+ MPU AXI MCU PLL12 PLL3 PLL4 RTC MCO1 MCO2
+
+ with value equals to RCC clock specifier as defined in
+ dt-bindings/clock/stm32mp1-clksrc.h: CLK_<NAME>_<SOURCE>
+
+- st,clkdiv : The div parameters in this order
+ for STM32MP15x: 11 dividers value are requested
+ MPU AXI MCU APB1 APB2 APB3 APB4 APB5 RTC MCO1 MCO2
+
+ with DIV coding defined in RCC associated register RCC_xxxDIVR
+
+ most the case, it is:
+ 0x0: not divided
+ 0x1: division by 2
+ 0x2: division by 4
+ 0x3: division by 8
+ ...
+
+ but for RTC MCO1 MCO2, the coding is different:
+ 0x0: not divided
+ 0x1: division by 2
+ 0x2: division by 3
+ 0x3: division by 4
+ ...
+
+Optional Properties:
+- st,pll
+ PLL children node for PLL1 to PLL4 : (see ref manual for details)
+ with associated index 0 to 3 (st,pll@0 to st,pll@4)
+ PLLx is off when the associated node is absent
+
+ - Sub-nodes:
+
+ - cfg: The parameters for PLL configuration in this order:
+ DIVM DIVN DIVP DIVQ DIVR Output
+
+ with DIV value as defined in RCC spec:
+ 0x0: bypass (division by 1)
+ 0x1: division by 2
+ 0x2: division by 3
+ 0x3: division by 4
+ ...
+
+ and Output = bitfield for each output value = 1:ON/0:OFF
+ BIT(0) => output P : DIVPEN
+ BIT(1) => output Q : DIVQEN
+ BIT(2) => output R : DIVREN
+ NB : macro PQR(p,q,r) can be used to build this value
+ with p,p,r = 0 or 1
+
+ - frac : Fractional part of the multiplication factor
+ (optional, PLL is in integer mode when absent)
+
+ - csg : Clock Spreading Generator (optional)
+ with parameters in this order:
+ MOD_PER INC_STEP SSCG_MODE
+
+ * MOD_PER: Modulation Period Adjustment
+ * INC_STEP: Modulation Depth Adjustment
+ * SSCG_MODE: Spread spectrum clock generator mode
+ you can use associated defines from stm32mp1-clksrc.h
+ * SSCG_MODE_CENTER_SPREAD = 0
+ * SSCG_MODE_DOWN_SPREAD = 1
+
+
+- st,pkcs : used to configure the peripherals kernel clock selection
+ containing a list of peripheral kernel clock source identifier as defined
+ in the file dt-bindings/clock/stm32mp1-clksrc.h
+
+ Example:
+
+ rcc: rcc@50000000 {
+ compatible = "syscon", "simple-mfd";
+
+ reg = <0x50000000 0x1000>;
+
+ rcc_clk: rcc-clk@50000000 {
+ #clock-cells = <1>;
+ compatible = "st,stm32mp1-rcc-clk";
+
+ st,clksrc = < CLK_MPU_PLL1P
+ CLK_AXI_PLL2P
+ CLK_MCU_HSI
+ CLK_PLL12_HSE
+ CLK_PLL3_HSE
+ CLK_PLL4_HSE
+ CLK_RTC_HSE
+ CLK_MCO1_DISABLED
+ CLK_MCO2_DISABLED
+ >;
+
+ st,clkdiv = <
+ 1 /*MPU*/
+ 0 /*AXI*/
+ 0 /*MCU*/
+ 1 /*APB1*/
+ 1 /*APB2*/
+ 1 /*APB3*/
+ 1 /*APB4*/
+ 5 /*APB5*/
+ 23 /*RTC*/
+ 0 /*MCO1*/
+ 0 /*MCO2*/
+ >;
+
+ st,pll@0 {
+ cfg = < 1 53 0 0 0 1 >;
+ frac = < 0x810 >;
+ };
+ st,pll@1 {
+ cfg = < 1 43 1 0 0 PQR(0,1,1)>;
+ csg = <10 20 1>;
+ };
+ st,pll@2 {
+ cfg = < 2 85 3 13 3 0>;
+ csg = <10 20 SSCG_MODE_CENTER_SPREAD>;
+ };
+ st,pll@3 {
+ cfg = < 2 78 4 7 9 3>;
+ };
+ st,pkcs = <
+ CLK_STGEN_HSE
+ CLK_CKPER_HSI
+ CLK_USBPHY_PLL2P
+ CLK_DSI_PLL2Q
+ >;
+ };
+ };
+
+--------------------------
+other clocks = fixed-clock
+--------------------------
+The clock tree is also based on 5 fixed-clock in clocks node
+used to define the state of associated ST32MP1 oscillators:
+- clk-lsi
+- clk-lse
+- clk-hsi
+- clk-hse
+- clk-csi
+
+At boot the clock tree initialization will
+- enable the oscillator present in device tree
+- disable HSI oscillator if the node is absent (always activated by bootrom)
+
+Optional properties :
+
+a) for external oscillator: "clk-lse", "clk-hse"
+
+ 3 optional fields are managed
+ - "st,bypass" Configure the oscillator bypass mode (HSEBYP, LSEBYP)
+ - "st,css" Activate the clock security system (HSECSSON, LSECSSON)
+ - "st,drive" (only for LSE) value of the drive for the oscillator
+ (see LSEDRV_ define in the file dt-bindings/clock/stm32mp1-clksrc.h)
+
+ Example board file:
+
+ / {
+ clocks {
+ clk_hse: clk-hse {
+ #clock-cells = <0>;
+ compatible = "fixed-clock";
+ clock-frequency = <64000000>;
+ st,bypass;
+ };
+
+ clk_lse: clk-lse {
+ #clock-cells = <0>;
+ compatible = "fixed-clock";
+ clock-frequency = <32768>;
+ st,css;
+ st,drive = <LSEDRV_LOWEST>;
+ };
+ };
+
+b) for internal oscillator: "clk-hsi"
+
+ internally HSI clock is fixed to 64MHz for STM32MP157 soc
+ in device tree clk-hsi is the clock after HSIDIV (ck_hsi in RCC doc)
+ So this clock frequency is used to compute the expected HSI_DIV
+ for the clock tree initialisation
+
+ ex: for HSIDIV = /1
+
+ / {
+ clocks {
+ clk_hsi: clk-hsi {
+ #clock-cells = <0>;
+ compatible = "fixed-clock";
+ clock-frequency = <64000000>;
+ };
+ };
+
+ ex: for HSIDIV = /2
+
+ / {
+ clocks {
+ clk_hsi: clk-hsi {
+ #clock-cells = <0>;
+ compatible = "fixed-clock";
+ clock-frequency = <32000000>;
+ };
+ };
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