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clk: fractional-divider: Export approximation algorithm to the CCF users

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At least one user currently duplicates some functions that are provided
by fractional divider module. Let's export approximation algorithm and
replace the open-coded variant.

As a bonus the exported function will get better documentation in place.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20210812170025.67074-1-andriy.shevchenko@linux.intel.com
[sboyd@kernel.org: Add header guard because why not]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
This commit is contained in:
Andy Shevchenko 2021-08-12 20:00:22 +03:00 committed by Stephen Boyd
parent e73f0f0ee7
commit 4e7cf74fa3
3 changed files with 23 additions and 18 deletions
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11
drivers/clk/clk-fractional-divider.c
View File

@ -14,6 +14,8 @@
#include <linux/slab.h>
#include <linux/rational.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)
@ -68,9 +70,10 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
return ret;
}
static void clk_fd_general_approximation(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate,
unsigned long *m, unsigned long *n)
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);
unsigned long scale;
@ -102,7 +105,7 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
if (fd->approximation)
fd->approximation(hw, rate, parent_rate, &m, &n);
else
clk_fd_general_approximation(hw, rate, parent_rate, &m, &n);
clk_fractional_divider_general_approximation(hw, rate, parent_rate, &m, &n);
ret = (u64)*parent_rate * m;
do_div(ret, n);

13
drivers/clk/clk-fractional-divider.h Normal file
View File

@ -0,0 +1,13 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _CLK_FRACTIONAL_DIV_H
#define _CLK_FRACTIONAL_DIV_H
struct clk_hw;
void clk_fractional_divider_general_approximation(struct clk_hw *hw,
unsigned long rate,
unsigned long *parent_rate,
unsigned long *m,
unsigned long *n);
#endif

17
drivers/clk/rockchip/clk.c
View File

@ -22,6 +22,8 @@
#include <linux/regmap.h>
#include <linux/reboot.h>
#include <linux/rational.h>
#include "../clk-fractional-divider.h"
#include "clk.h"
/*
@ -178,10 +180,8 @@ static void rockchip_fractional_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);
unsigned long p_rate, p_parent_rate;
struct clk_hw *p_parent;
unsigned long scale;
p_rate = clk_hw_get_rate(clk_hw_get_parent(hw));
if ((rate * 20 > p_rate) && (p_rate % rate != 0)) {
@ -190,18 +190,7 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
*parent_rate = p_parent_rate;
}
/*
* 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.
*/
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);
clk_fractional_divider_general_approximation(hw, rate, parent_rate, m, n);
}
static struct clk *rockchip_clk_register_frac_branch(