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![Simon Glass](/assets/img/avatar_default.png)
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>
59 lines
1.0 KiB
C
59 lines
1.0 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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#include <common.h>
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#include <clk.h>
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#include <dm.h>
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#include <errno.h>
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#include <dm/lists.h>
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#include <dm/root.h>
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ulong clk_get_rate(struct udevice *dev)
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{
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struct clk_ops *ops = clk_get_ops(dev);
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if (!ops->get_rate)
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return -ENOSYS;
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return ops->get_rate(dev);
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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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struct clk_ops *ops = clk_get_ops(dev);
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if (!ops->set_rate)
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return -ENOSYS;
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return ops->set_rate(dev, rate);
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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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struct clk_ops *ops = clk_get_ops(dev);
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if (!ops->get_periph_rate)
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return -ENOSYS;
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return ops->get_periph_rate(dev, periph);
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}
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ulong clk_set_periph_rate(struct udevice *dev, int periph, ulong rate)
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{
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struct clk_ops *ops = clk_get_ops(dev);
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if (!ops->set_periph_rate)
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return -ENOSYS;
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return ops->set_periph_rate(dev, periph, rate);
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}
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UCLASS_DRIVER(clk) = {
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.id = UCLASS_CLK,
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.name = "clk",
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};
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