Contributors: 12
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Heikki Krogerus |
550 |
41.60% |
2 |
7.14% |
| Andy Shevchenko |
350 |
26.48% |
9 |
32.14% |
| Stephen Boyd |
138 |
10.44% |
4 |
14.29% |
| Jonas Gorski |
75 |
5.67% |
2 |
7.14% |
| Michael Turquette |
68 |
5.14% |
2 |
7.14% |
| Elaine Zhang |
49 |
3.71% |
1 |
3.57% |
| Dong Aisheng |
32 |
2.42% |
1 |
3.57% |
| James Hogan |
30 |
2.27% |
2 |
7.14% |
| Russell King |
18 |
1.36% |
2 |
7.14% |
| Katsuhiro Suzuki |
8 |
0.61% |
1 |
3.57% |
| Heiko Stübner |
3 |
0.23% |
1 |
3.57% |
| Tom Rix |
1 |
0.08% |
1 |
3.57% |
| Total |
1322 |
|
28 |
|
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2014 Intel Corporation
*
* Adjustable fractional divider clock implementation.
* Uses rational best approximation algorithm.
*
* Output is calculated as
*
* rate = (m / n) * parent_rate (1)
*
* This is useful when we have a prescaler block which asks for
* m (numerator) and n (denominator) values to be provided to satisfy
* the (1) as much as possible.
*
* Since m and n have the limitation by a range, e.g.
*
* n >= 1, n < N_width, where N_width = 2^nwidth (2)
*
* for some cases the output may be saturated. Hence, from (1) and (2),
* assuming the worst case when m = 1, the inequality
*
* floor(log2(parent_rate / rate)) <= nwidth (3)
*
* may be derived. Thus, in cases when
*
* (parent_rate / rate) >> N_width (4)
*
* we might scale up the rate by 2^scale (see the description of
* CLK_FRAC_DIVIDER_POWER_OF_TWO_PS for additional information), where
*
* scale = floor(log2(parent_rate / rate)) - nwidth (5)
*
* and assume that the IP, that needs m and n, has also its own
* prescaler, which is capable to divide by 2^scale. In this way
* we get the denominator to satisfy the desired range (2) and
* at the same time a much better result of m and n than simple
* saturated values.
*/
#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/rational.h>
#include <linux/slab.h>
#include <linux/clk-provider.h>
#include "clk-fractional-divider.h"
static inline u32 clk_fd_readl(struct clk_fractional_divider *fd)
{
if (fd->flags & CLK_FRAC_DIVIDER_BIG_ENDIAN)
return ioread32be(fd->reg);
return readl(fd->reg);
}
static inline void clk_fd_writel(struct clk_fractional_divider *fd, u32 val)
{
if (fd->flags & CLK_FRAC_DIVIDER_BIG_ENDIAN)
iowrite32be(val, fd->reg);
else
writel(val, fd->reg);
}
static void clk_fd_get_div(struct clk_hw *hw, struct u32_fract *fract)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
unsigned long flags = 0;
unsigned long m, n;
u32 val;
if (fd->lock)
spin_lock_irqsave(fd->lock, flags);
else
__acquire(fd->lock);
val = clk_fd_readl(fd);
if (fd->lock)
spin_unlock_irqrestore(fd->lock, flags);
else
__release(fd->lock);
m = (val & fd->mmask) >> fd->mshift;
n = (val & fd->nmask) >> fd->nshift;
if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {
m++;
n++;
}
fract->numerator = m;
fract->denominator = n;
}
static unsigned long clk_fd_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
{
struct u32_fract fract;
u64 ret;
clk_fd_get_div(hw, &fract);
if (!fract.numerator || !fract.denominator)
return parent_rate;
ret = (u64)parent_rate * fract.numerator;
do_div(ret, fract.denominator);
return ret;
}
void clk_fractional_divider_general_approximation(struct clk_hw *hw,
unsigned long rate,
unsigned long *parent_rate,
unsigned long *m, unsigned long *n)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
/*
* Get rate closer to *parent_rate to guarantee there is no overflow
* for m and n. In the result it will be the nearest rate left shifted
* by (scale - fd->nwidth) bits.
*
* For the detailed explanation see the top comment in this file.
*/
if (fd->flags & CLK_FRAC_DIVIDER_POWER_OF_TWO_PS) {
unsigned long scale = fls_long(*parent_rate / rate - 1);
if (scale > fd->nwidth)
rate <<= scale - fd->nwidth;
}
rational_best_approximation(rate, *parent_rate,
GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
m, n);
}
static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
unsigned long m, n;
u64 ret;
if (!rate || (!clk_hw_can_set_rate_parent(hw) && rate >= *parent_rate))
return *parent_rate;
if (fd->approximation)
fd->approximation(hw, rate, parent_rate, &m, &n);
else
clk_fractional_divider_general_approximation(hw, rate, parent_rate, &m, &n);
ret = (u64)*parent_rate * m;
do_div(ret, n);
return ret;
}
static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct clk_fractional_divider *fd = to_clk_fd(hw);
unsigned long flags = 0;
unsigned long m, n;
u32 val;
rational_best_approximation(rate, parent_rate,
GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
&m, &n);
if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {
m--;
n--;
}
if (fd->lock)
spin_lock_irqsave(fd->lock, flags);
else
__acquire(fd->lock);
val = clk_fd_readl(fd);
val &= ~(fd->mmask | fd->nmask);
val |= (m << fd->mshift) | (n << fd->nshift);
clk_fd_writel(fd, val);
if (fd->lock)
spin_unlock_irqrestore(fd->lock, flags);
else
__release(fd->lock);
return 0;
}
#ifdef CONFIG_DEBUG_FS
static int clk_fd_numerator_get(void *hw, u64 *val)
{
struct u32_fract fract;
clk_fd_get_div(hw, &fract);
*val = fract.numerator;
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(clk_fd_numerator_fops, clk_fd_numerator_get, NULL, "%llu\n");
static int clk_fd_denominator_get(void *hw, u64 *val)
{
struct u32_fract fract;
clk_fd_get_div(hw, &fract);
*val = fract.denominator;
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(clk_fd_denominator_fops, clk_fd_denominator_get, NULL, "%llu\n");
static void clk_fd_debug_init(struct clk_hw *hw, struct dentry *dentry)
{
debugfs_create_file("numerator", 0444, dentry, hw, &clk_fd_numerator_fops);
debugfs_create_file("denominator", 0444, dentry, hw, &clk_fd_denominator_fops);
}
#endif
const struct clk_ops clk_fractional_divider_ops = {
.recalc_rate = clk_fd_recalc_rate,
.round_rate = clk_fd_round_rate,
.set_rate = clk_fd_set_rate,
#ifdef CONFIG_DEBUG_FS
.debug_init = clk_fd_debug_init,
#endif
};
EXPORT_SYMBOL_GPL(clk_fractional_divider_ops);
struct clk_hw *clk_hw_register_fractional_divider(struct device *dev,
const char *name, const char *parent_name, unsigned long flags,
void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
u8 clk_divider_flags, spinlock_t *lock)
{
struct clk_fractional_divider *fd;
struct clk_init_data init;
struct clk_hw *hw;
int ret;
fd = kzalloc(sizeof(*fd), GFP_KERNEL);
if (!fd)
return ERR_PTR(-ENOMEM);
init.name = name;
init.ops = &clk_fractional_divider_ops;
init.flags = flags;
init.parent_names = parent_name ? &parent_name : NULL;
init.num_parents = parent_name ? 1 : 0;
fd->reg = reg;
fd->mshift = mshift;
fd->mwidth = mwidth;
fd->mmask = GENMASK(mwidth - 1, 0) << mshift;
fd->nshift = nshift;
fd->nwidth = nwidth;
fd->nmask = GENMASK(nwidth - 1, 0) << nshift;
fd->flags = clk_divider_flags;
fd->lock = lock;
fd->hw.init = &init;
hw = &fd->hw;
ret = clk_hw_register(dev, hw);
if (ret) {
kfree(fd);
hw = ERR_PTR(ret);
}
return hw;
}
EXPORT_SYMBOL_GPL(clk_hw_register_fractional_divider);
struct clk *clk_register_fractional_divider(struct device *dev,
const char *name, const char *parent_name, unsigned long flags,
void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
u8 clk_divider_flags, spinlock_t *lock)
{
struct clk_hw *hw;
hw = clk_hw_register_fractional_divider(dev, name, parent_name, flags,
reg, mshift, mwidth, nshift, nwidth, clk_divider_flags,
lock);
if (IS_ERR(hw))
return ERR_CAST(hw);
return hw->clk;
}
EXPORT_SYMBOL_GPL(clk_register_fractional_divider);
void clk_hw_unregister_fractional_divider(struct clk_hw *hw)
{
struct clk_fractional_divider *fd;
fd = to_clk_fd(hw);
clk_hw_unregister(hw);
kfree(fd);
}