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# Copyright (c) 2021, Linaro ltd
# SPDX-License-Identifier: Apache-2.0
description: |
STM32 Reset and Clock controller node for STM32H7 devices
This node is in charge of system clock ('SYSCLK') source selection and
System Clock Generation.
Configuring STM32 Reset and Clock controller node:
System clock source should be selected amongst the clock nodes available in "clocks"
node (typically 'clk_hse, clk_csi', 'pll', ...).
As part of this node configuration, SYSCLK frequency should also be defined, using
"clock-frequency" property.
Last, bus clocks (typically HCLK, PCLK1, PCLK2) should be configured using matching
prescaler properties.
Here is an example of correctly configured rcc node:
&rcc {
clocks = <&pll>; /* Set pll as SYSCLK source */
clock-frequency = <DT_FREQ_M(480)>; /* SYSCLK runs at 480MHz */
d1cpre = <1>;
hpre = <1>;
d1ppre = <1>;
d2ppre1 = <1>;
d2ppre2 = <1>;
d3ppre = <1>;
}
Specifying a gated clock:
To specify a gated clock, a peripheral should define a "clocks" property encoded
in the following way:
... {
...
clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00000020>;
...
}
After the phandle referring to rcc node, the first index specifies the registers of
the bus controlling the peripheral and the second index specifies the bit used to
control the peripheral clock in that bus register.
compatible: "st,stm32h7-rcc"
include: [clock-controller.yaml, base.yaml]
properties:
reg:
required: true
"#clock-cells":
const: 2
clock-frequency:
required: false
type: int
description: |
default frequency in Hz for clock output
d1cpre:
type: int
required: false
enum:
- 1
description: |
D1 Domain, CPU1 clock prescaler. Sets a HCLK frequency (feeding Cortex-M Systick)
lower than SYSCLK frequency (actual core frequency).
Zephyr doesn't make a difference today between these two clocks.
Changing this prescaler is not allowed until it is made possible to
use them independently in Zephyr clock subsystem.
hpre:
type: int
required: false
description: |
D2 domain, CPU2 core clock and AHB(1/2/3/4) peripheral prescaler
enum:
- 1
- 2
- 4
- 8
- 16
- 64
- 128
- 256
- 512
d1ppre:
type: int
required: false
description: |
D1 domain, APB3 peripheral prescaler
enum:
- 1
- 2
- 4
- 8
- 16
d2ppre1:
type: int
required: false
description: |
D2 domain, APB1 peripheral prescaler
enum:
- 1
- 2
- 4
- 8
- 16
d2ppre2:
type: int
required: false
description: |
D2 domain, APB2 peripheral prescaler
enum:
- 1
- 2
- 4
- 8
- 16
d3ppre:
type: int
required: false
description: |
D3 domain, APB4 peripheral prescaler
enum:
- 1
- 2
- 4
- 8
- 16
clock-cells:
- bus
- bits