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clk: meson: improve pll driver results with frac

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Finding the appropriate settings of meson plls is too tricky to be done
entirely at runtime, using calculation only. Many combination of m, n
and od won't lock which is why we are using a table for this.  However,
for plls having a fractional parameters, it is possible to improve on
the result provided by the table by calculating the frac parameter.

This change adds the calculation of frac when the parameter is available
and the rate provided by the table is not an exact match for the
requested rate.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
This commit is contained in:
Jerome Brunet 2018-02-19 12:21:39 +01:00 committed by Neil Armstrong
parent c178b003bf
commit 8289aafa4f
2 changed files with 91 additions and 59 deletions
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137
drivers/clk/meson/clk-pll.c
View File

@ -2,6 +2,9 @@
* Copyright (c) 2015 Endless Mobile, Inc.
* Author: Carlo Caione <carlo@endlessm.com>
*
* Copyright (c) 2018 Baylibre, SAS.
* Author: Jerome Brunet <jbrunet@baylibre.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
@ -27,7 +30,7 @@
* | |
* FREF VCO
*
* out = (in * M / N) >> OD
* out = in * (m + frac / frac_max) / (n << sum(ods))
*/
#include <linux/clk-provider.h>
@ -48,33 +51,85 @@ meson_clk_pll_data(struct clk_regmap *clk)
return (struct meson_clk_pll_data *)clk->data;
}
static unsigned long __pll_params_to_rate(unsigned long parent_rate,
const struct pll_rate_table *pllt,
u16 frac,
struct meson_clk_pll_data *pll)
{
u64 rate = (u64)parent_rate * pllt->m;
unsigned int od = pllt->od + pllt->od2 + pllt->od3;
if (frac && MESON_PARM_APPLICABLE(&pll->frac)) {
u64 frac_rate = (u64)parent_rate * frac;
rate += DIV_ROUND_UP_ULL(frac_rate,
(1 << pll->frac.width));
}
return DIV_ROUND_UP_ULL(rate, pllt->n << od);
}
static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_regmap *clk = to_clk_regmap(hw);
struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
u64 rate;
u16 n, m, frac = 0, od, od2 = 0, od3 = 0;
struct pll_rate_table pllt;
u16 frac;
n = meson_parm_read(clk->map, &pll->n);
m = meson_parm_read(clk->map, &pll->m);
od = meson_parm_read(clk->map, &pll->od);
pllt.n = meson_parm_read(clk->map, &pll->n);
pllt.m = meson_parm_read(clk->map, &pll->m);
pllt.od = meson_parm_read(clk->map, &pll->od);
if (MESON_PARM_APPLICABLE(&pll->od2))
od2 = meson_parm_read(clk->map, &pll->od2);
pllt.od2 = MESON_PARM_APPLICABLE(&pll->od2) ?
meson_parm_read(clk->map, &pll->od2) :
0;
if (MESON_PARM_APPLICABLE(&pll->od3))
od3 = meson_parm_read(clk->map, &pll->od3);
pllt.od3 = MESON_PARM_APPLICABLE(&pll->od3) ?
meson_parm_read(clk->map, &pll->od3) :
0;
rate = (u64)m * parent_rate;
frac = MESON_PARM_APPLICABLE(&pll->frac) ?
meson_parm_read(clk->map, &pll->frac) :
0;
if (MESON_PARM_APPLICABLE(&pll->frac)) {
frac = meson_parm_read(clk->map, &pll->frac);
return __pll_params_to_rate(parent_rate, &pllt, frac, pll);
}
rate += mul_u64_u32_shr(parent_rate, frac, pll->frac.width);
}
static u16 __pll_params_with_frac(unsigned long rate,
unsigned long parent_rate,
const struct pll_rate_table *pllt,
struct meson_clk_pll_data *pll)
{
u16 frac_max = (1 << pll->frac.width);
u64 val = (u64)rate * pllt->n;
return div_u64(rate, n) >> od >> od2 >> od3;
val <<= pllt->od + pllt->od2 + pllt->od3;
val = div_u64(val * frac_max, parent_rate);
val -= pllt->m * frac_max;
return min((u16)val, (u16)(frac_max - 1));
}
static const struct pll_rate_table *
meson_clk_get_pll_settings(unsigned long rate,
struct meson_clk_pll_data *pll)
{
const struct pll_rate_table *table = pll->table;
unsigned int i = 0;
if (!table)
return NULL;
/* Find the first table element exceeding rate */
while (table[i].rate && table[i].rate <= rate)
i++;
/* Select the setting of the rounded down rate */
if (i != 0)
i--;
return (struct pll_rate_table *)&table[i];
}
static long meson_clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
@ -82,39 +137,24 @@ static long meson_clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
{
struct clk_regmap *clk = to_clk_regmap(hw);
struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
const struct pll_rate_table *pllt;
const struct pll_rate_table *pllt =
meson_clk_get_pll_settings(rate, pll);
u16 frac;
/*
* if the table is missing, just return the current rate
* since we don't have the other available frequencies
*/
if (!pll->table)
if (!pllt)
return meson_clk_pll_recalc_rate(hw, *parent_rate);
for (pllt = pll->table; pllt->rate; pllt++) {
if (rate <= pllt->rate)
return pllt->rate;
}
if (!MESON_PARM_APPLICABLE(&pll->frac)
|| rate == pllt->rate)
return pllt->rate;
/* else return the smallest value */
return pll->table[0].rate;
}
/*
* The rate provided by the setting is not an exact match, let's
* try to improve the result using the fractional parameter
*/
frac = __pll_params_with_frac(rate, *parent_rate, pllt, pll);
static const struct pll_rate_table *
meson_clk_get_pll_settings(const struct pll_rate_table *table,
unsigned long rate)
{
const struct pll_rate_table *pllt;
if (!table)
return NULL;
for (pllt = table; pllt->rate; pllt++) {
if (rate == pllt->rate)
return pllt;
}
return NULL;
return __pll_params_to_rate(*parent_rate, pllt, frac, pll);
}
static int meson_clk_pll_wait_lock(struct clk_hw *hw)
@ -154,13 +194,14 @@ static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
const struct pll_rate_table *pllt;
unsigned long old_rate;
u16 frac = 0;
if (parent_rate == 0 || rate == 0)
return -EINVAL;
old_rate = rate;
pllt = meson_clk_get_pll_settings(pll->table, rate);
pllt = meson_clk_get_pll_settings(rate, pll);
if (!pllt)
return -EINVAL;
@ -177,8 +218,10 @@ static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
if (MESON_PARM_APPLICABLE(&pll->od3))
meson_parm_write(clk->map, &pll->od3, pllt->od3);
if (MESON_PARM_APPLICABLE(&pll->frac))
meson_parm_write(clk->map, &pll->frac, pllt->frac);
if (MESON_PARM_APPLICABLE(&pll->frac)) {
frac = __pll_params_with_frac(rate, parent_rate, pllt, pll);
meson_parm_write(clk->map, &pll->frac, frac);
}
/* make sure the reset is cleared at this point */
meson_parm_write(clk->map, &pll->rst, 0);

13
drivers/clk/meson/clkc.h
View File

@ -61,7 +61,6 @@ struct pll_rate_table {
u16 od;
u16 od2;
u16 od3;
u16 frac;
};
#define PLL_RATE(_r, _m, _n, _od) \
@ -70,17 +69,7 @@ struct pll_rate_table {
.m = (_m), \
.n = (_n), \
.od = (_od), \
} \
#define PLL_FRAC_RATE(_r, _m, _n, _od, _od2, _frac) \
{ \
.rate = (_r), \
.m = (_m), \
.n = (_n), \
.od = (_od), \
.od2 = (_od2), \
.frac = (_frac), \
} \
}
struct meson_clk_pll_data {
struct parm m;