dt-bindings: Document STM32MP1 Reset Clock Controller (RCC) bindings

The RCC block is responsible of the management of the clock and reset
generation for the complete circuit.

Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
This commit is contained in:
Gabriel Fernandez 2018-03-08 17:53:54 +01:00 committed by Michael Turquette
parent 7928b2cbe5
commit 605add0c7b

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STMicroelectronics STM32 Peripheral Reset Clock Controller
==========================================================
The RCC IP is both a reset and a clock controller.
RCC makes also power management (resume/supend and wakeup interrupt).
Please also refer to reset.txt for common reset controller binding usage.
Please also refer to clock-bindings.txt for common clock controller
binding usage.
Required properties:
- compatible: "st,stm32mp1-rcc", "syscon"
- reg: should be register base and length as documented in the datasheet
- #clock-cells: 1, device nodes should specify the clock in their
"clocks" property, containing a phandle to the clock device node,
an index specifying the clock to use.
- #reset-cells: Shall be 1
- interrupts: Should contain a general interrupt line and a interrupt line
to the wake-up of processor (CSTOP).
Example:
rcc: rcc@50000000 {
compatible = "st,stm32mp1-rcc", "syscon";
reg = <0x50000000 0x1000>;
#clock-cells = <1>;
#reset-cells = <1>;
interrupts = <GIC_SPI 5 IRQ_TYPE_NONE>,
<GIC_SPI 145 IRQ_TYPE_NONE>;
};
Specifying clocks
=================
All available clocks are defined as preprocessor macros in
dt-bindings/clock/stm32mp1-clks.h header and can be used in device
tree sources.
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 on STM32MP1, for LTDC reset:
ltdc = APB4_RSTSETR_offset / 4 * 32 + LTDC_bit_offset
= 0x180 / 4 * 32 + 0 = 3072
The list of valid indices for STM32MP1 is available in:
include/dt-bindings/reset-controller/stm32mp1-resets.h
This file implements defines like:
#define LTDC_R 3072