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Clocks are an important feature of platforms and have become increasing complex with time. Most modern SoCs have multiple PLLs and dozens of clock dividers which distribute clocks to on-chip peripherals. Some SoC implementations have a clock API which is private to that SoC family, e.g. Tegra and Exynos. This is useful but it would be better to have a common API that can be understood and used throughout U-Boot. Add a simple clock API as a starting point. It supports querying and setting the rate of a clock. Each clock is a device. To reduce memory and processing overhead the concept of peripheral clocks is provided. These do not need to be explicit devices - it is possible to write a driver that can adjust the I2C clock (for example) without an explicit I2C clock device. This can dramatically reduce the number of devices (and associated overhead) in a complex SoC. Clocks are referenced by a number, and it is expected that SoCs will define that numbering themselves via an enum. Signed-off-by: Simon Glass <sjg@chromium.org>
86 lines
2 KiB
C
86 lines
2 KiB
C
/*
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* Copyright (c) 2015 Google, Inc
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* Written by Simon Glass <sjg@chromium.org>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#ifndef _CLK_H_
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#define _CLK_H_
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int soc_clk_dump(void);
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struct clk_ops {
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/**
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* get_rate() - Get current clock rate
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*
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* @dev: Device to check (UCLASS_CLK)
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* @return clock rate in Hz, or -ve error code
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*/
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ulong (*get_rate)(struct udevice *dev);
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/**
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* set_rate() - Set current clock rate
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*
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* @dev: Device to adjust
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* @rate: New clock rate in Hz
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* @return new rate, or -ve error code
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*/
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ulong (*set_rate)(struct udevice *dev, ulong rate);
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/**
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* clk_set_periph_rate() - Set clock rate for a peripheral
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*
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* @dev: Device to adjust (UCLASS_CLK)
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* @rate: New clock rate in Hz
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* @return new clock rate in Hz, or -ve error code
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*/
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ulong (*get_periph_rate)(struct udevice *dev, int periph);
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/**
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* clk_set_periph_rate() - Set current clock rate for a peripheral
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*
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* @dev: Device to update (UCLASS_CLK)
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* @periph: Peripheral ID to cupdate
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* @return new clock rate in Hz, or -ve error code
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*/
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ulong (*set_periph_rate)(struct udevice *dev, int periph, ulong rate);
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};
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#define clk_get_ops(dev) ((struct clk_ops *)(dev)->driver->ops)
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/**
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* clk_get_rate() - Get current clock rate
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*
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* @dev: Device to check (UCLASS_CLK)
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* @return clock rate in Hz, or -ve error code
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*/
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ulong clk_get_rate(struct udevice *dev);
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/**
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* set_rate() - Set current clock rate
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*
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* @dev: Device to adjust
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* @rate: New clock rate in Hz
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* @return new rate, or -ve error code
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*/
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ulong clk_set_rate(struct udevice *dev, ulong rate);
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/**
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* clk_get_periph_rate() - Get current clock rate for a peripheral
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*
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* @dev: Device to check (UCLASS_CLK)
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* @return clock rate in Hz, -ve error code
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*/
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ulong clk_get_periph_rate(struct udevice *dev, int periph);
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/**
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* clk_set_periph_rate() - Set current clock rate for a peripheral
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*
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* @dev: Device to update (UCLASS_CLK)
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* @periph: Peripheral ID to cupdate
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* @return new clock rate in Hz, or -ve error code
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*/
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ulong clk_set_periph_rate(struct udevice *dev, int periph, ulong rate);
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#endif /* _CLK_H_ */
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