linux/drivers/clk/clk-mux.c

/*
 * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
 * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Simple multiplexer clock implementation
 */

#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/err.h>

/*
 * DOC: basic adjustable multiplexer clock that cannot gate
 *
 * Traits of this clock:
 * prepare - clk_prepare only ensures that parents are prepared
 * enable - clk_enable only ensures that parents are enabled
 * rate - rate is only affected by parent switching.  No clk_set_rate support
 * parent - parent is adjustable through clk_set_parent
 */

#define to_clk_mux(_hw) container_of(_hw, struct clk_mux, hw)

static u8 clk_mux_get_parent(struct clk_hw *hw)
{
	struct clk_mux *mux = to_clk_mux(hw);
	u32 val;

	/*
	 * FIXME need a mux-specific flag to determine if val is bitwise or numeric
	 * e.g. sys_clkin_ck's clksel field is 3 bits wide, but ranges from 0x1
	 * to 0x7 (index starts at one)
	 * OTOH, pmd_trace_clk_mux_ck uses a separate bit for each clock, so
	 * val = 0x4 really means "bit 2, index starts at bit 0"
	 */
	val = readl(mux->reg) >> mux->shift;
	val &= (1 << mux->width) - 1;

	if (val && (mux->flags & CLK_MUX_INDEX_BIT))
		val = ffs(val) - 1;

	if (val && (mux->flags & CLK_MUX_INDEX_ONE))
		val--;

	if (val >= __clk_get_num_parents(hw->clk))
		return -EINVAL;

	return val;
}

static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
{
	struct clk_mux *mux = to_clk_mux(hw);
	u32 val;
	unsigned long flags = 0;

	if (mux->flags & CLK_MUX_INDEX_BIT)
		index = (1 << ffs(index));

	if (mux->flags & CLK_MUX_INDEX_ONE)
		index++;

	if (mux->lock)
		spin_lock_irqsave(mux->lock, flags);

	val = readl(mux->reg);
	val &= ~(((1 << mux->width) - 1) << mux->shift);
	val |= index << mux->shift;
	writel(val, mux->reg);

	if (mux->lock)
		spin_unlock_irqrestore(mux->lock, flags);

	return 0;
}

struct clk_ops clk_mux_ops = {
	.get_parent = clk_mux_get_parent,
	.set_parent = clk_mux_set_parent,
};
EXPORT_SYMBOL_GPL(clk_mux_ops);

struct clk *clk_register_mux(struct device *dev, const char *name,
		char **parent_names, u8 num_parents, unsigned long flags,
		void __iomem *reg, u8 shift, u8 width,
		u8 clk_mux_flags, spinlock_t *lock)
{
	struct clk_mux *mux;

	mux = kzalloc(sizeof(struct clk_mux), GFP_KERNEL);

	if (!mux) {
		pr_err("%s: could not allocate mux clk\n", __func__);
		return ERR_PTR(-ENOMEM);
	}

	/* struct clk_mux assignments */
	mux->reg = reg;
	mux->shift = shift;
	mux->width = width;
	mux->flags = clk_mux_flags;
	mux->lock = lock;

	return clk_register(dev, name, &clk_mux_ops, &mux->hw,
			parent_names, num_parents, flags);
}