clk-frac-synth.c
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/*
* Copyright (C) 2012 ST Microelectronics
* Viresh Kumar <vireshk@kernel.org>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*
* Fractional Synthesizer clock implementation
*/
#define pr_fmt(fmt) "clk-frac-synth: " fmt
#include <linux/clk-provider.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/err.h>
#include "clk.h"
#define DIV_FACTOR_MASK 0x1FFFF
/*
* DOC: Fractional Synthesizer clock
*
* Fout from synthesizer can be given from below equation:
*
* Fout= Fin/2*div (division factor)
* div is 17 bits:-
* 0-13 (fractional part)
* 14-16 (integer part)
* div is (16-14 bits).(13-0 bits) (in binary)
*
* Fout = Fin/(2 * div)
* Fout = ((Fin / 10000)/(2 * div)) * 10000
* Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000
* Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000
*
* div << 14 simply 17 bit value written at register.
* Max error due to scaling down by 10000 is 10 KHz
*/
#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)
static unsigned long frac_calc_rate(struct clk_hw *hw, unsigned long prate,
int index)
{
struct clk_frac *frac = to_clk_frac(hw);
struct frac_rate_tbl *rtbl = frac->rtbl;
prate /= 10000;
prate <<= 14;
prate /= (2 * rtbl[index].div);
prate *= 10000;
return prate;
}
static long clk_frac_round_rate(struct clk_hw *hw, unsigned long drate,
unsigned long *prate)
{
struct clk_frac *frac = to_clk_frac(hw);
int unused;
return clk_round_rate_index(hw, drate, *prate, frac_calc_rate,
frac->rtbl_cnt, &unused);
}
static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_frac *frac = to_clk_frac(hw);
unsigned long flags = 0;
unsigned int div = 1, val;
if (frac->lock)
spin_lock_irqsave(frac->lock, flags);
val = readl_relaxed(frac->reg);
if (frac->lock)
spin_unlock_irqrestore(frac->lock, flags);
div = val & DIV_FACTOR_MASK;
if (!div)
return 0;
parent_rate = parent_rate / 10000;
parent_rate = (parent_rate << 14) / (2 * div);
return parent_rate * 10000;
}
/* Configures new clock rate of frac */
static int clk_frac_set_rate(struct clk_hw *hw, unsigned long drate,
unsigned long prate)
{
struct clk_frac *frac = to_clk_frac(hw);
struct frac_rate_tbl *rtbl = frac->rtbl;
unsigned long flags = 0, val;
int i;
clk_round_rate_index(hw, drate, prate, frac_calc_rate, frac->rtbl_cnt,
&i);
if (frac->lock)
spin_lock_irqsave(frac->lock, flags);
val = readl_relaxed(frac->reg) & ~DIV_FACTOR_MASK;
val |= rtbl[i].div & DIV_FACTOR_MASK;
writel_relaxed(val, frac->reg);
if (frac->lock)
spin_unlock_irqrestore(frac->lock, flags);
return 0;
}
static struct clk_ops clk_frac_ops = {
.recalc_rate = clk_frac_recalc_rate,
.round_rate = clk_frac_round_rate,
.set_rate = clk_frac_set_rate,
};
struct clk *clk_register_frac(const char *name, const char *parent_name,
unsigned long flags, void __iomem *reg,
struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock)
{
struct clk_init_data init;
struct clk_frac *frac;
struct clk *clk;
if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
pr_err("Invalid arguments passed");
return ERR_PTR(-EINVAL);
}
frac = kzalloc(sizeof(*frac), GFP_KERNEL);
if (!frac) {
pr_err("could not allocate frac clk\n");
return ERR_PTR(-ENOMEM);
}
/* struct clk_frac assignments */
frac->reg = reg;
frac->rtbl = rtbl;
frac->rtbl_cnt = rtbl_cnt;
frac->lock = lock;
frac->hw.init = &init;
init.name = name;
init.ops = &clk_frac_ops;
init.flags = flags;
init.parent_names = &parent_name;
init.num_parents = 1;
clk = clk_register(NULL, &frac->hw);
if (!IS_ERR_OR_NULL(clk))
return clk;
pr_err("clk register failed\n");
kfree(frac);
return NULL;
}