Re: [PATCH 3/3] clk: meson: clk-pll: drop hard-coded rates from pll tables

From: Martin Blumenstingl
Date: Sat Jul 21 2018 - 16:16:40 EST

On Thu, Jul 19, 2018 at 10:44 AM Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
>
> On 17/07/2018 11:56, Jerome Brunet wrote:
> > Putting hard-coded rates inside the parameter tables assumes that
> > the parent is known and will never change. That's a big assumption
> > we should not make.
> >
> > We have everything we need to recalculate the output rate using
> > the parent rate and the rest of the parameters. Let's do so and
> > drop the rates from the tables.
> >
> > Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> > ---
> > drivers/clk/meson/axg.c | 73 +++++++++++++--------------
> > drivers/clk/meson/clk-pll.c | 69 ++++++++++++++++---------
> > drivers/clk/meson/clkc.h | 8 ++-
> > drivers/clk/meson/gxbb.c | 120 ++++++++++++++++++++++----------------------
> > drivers/clk/meson/meson8b.c | 34 ++++++-------
> > 5 files changed, 162 insertions(+), 142 deletions(-)
> >
> > diff --git a/drivers/clk/meson/axg.c b/drivers/clk/meson/axg.c
> > index 572358062459..d34954bd8c5e 100644
> > --- a/drivers/clk/meson/axg.c
> > +++ b/drivers/clk/meson/axg.c
> > @@ -130,36 +130,36 @@ static struct clk_regmap axg_sys_pll = {
> > },
> > };
> >
> > -static const struct pll_rate_table axg_gp0_pll_rate_table[] = {
> > - PLL_RATE(960000000, 40, 1),
> > - PLL_RATE(984000000, 41, 1),
> > - PLL_RATE(1008000000, 42, 1),
> > - PLL_RATE(1032000000, 43, 1),
> > - PLL_RATE(1056000000, 44, 1),
> > - PLL_RATE(1080000000, 45, 1),
> > - PLL_RATE(1104000000, 46, 1),
> > - PLL_RATE(1128000000, 47, 1),
> > - PLL_RATE(1152000000, 48, 1),
> > - PLL_RATE(1176000000, 49, 1),
> > - PLL_RATE(1200000000, 50, 1),
> > - PLL_RATE(1224000000, 51, 1),
> > - PLL_RATE(1248000000, 52, 1),
> > - PLL_RATE(1272000000, 53, 1),
> > - PLL_RATE(1296000000, 54, 1),
> > - PLL_RATE(1320000000, 55, 1),
> > - PLL_RATE(1344000000, 56, 1),
> > - PLL_RATE(1368000000, 57, 1),
> > - PLL_RATE(1392000000, 58, 1),
> > - PLL_RATE(1416000000, 59, 1),
> > - PLL_RATE(1440000000, 60, 1),
> > - PLL_RATE(1464000000, 61, 1),
> > - PLL_RATE(1488000000, 62, 1),
> > - PLL_RATE(1512000000, 63, 1),
> > - PLL_RATE(1536000000, 64, 1),
> > - PLL_RATE(1560000000, 65, 1),
> > - PLL_RATE(1584000000, 66, 1),
> > - PLL_RATE(1608000000, 67, 1),
> > - PLL_RATE(1632000000, 68, 1),
> > +static const struct pll_params_table axg_gp0_pll_params_table[] = {
> > + PLL_PARAMS(40, 1),
> > + PLL_PARAMS(41, 1),
> > + PLL_PARAMS(42, 1),
> > + PLL_PARAMS(43, 1),
> > + PLL_PARAMS(44, 1),
> > + PLL_PARAMS(45, 1),
> > + PLL_PARAMS(46, 1),
> > + PLL_PARAMS(47, 1),
> > + PLL_PARAMS(48, 1),
> > + PLL_PARAMS(49, 1),
> > + PLL_PARAMS(50, 1),
> > + PLL_PARAMS(51, 1),
> > + PLL_PARAMS(52, 1),
> > + PLL_PARAMS(53, 1),
> > + PLL_PARAMS(54, 1),
> > + PLL_PARAMS(55, 1),
> > + PLL_PARAMS(56, 1),
> > + PLL_PARAMS(57, 1),
> > + PLL_PARAMS(58, 1),
> > + PLL_PARAMS(59, 1),
> > + PLL_PARAMS(60, 1),
> > + PLL_PARAMS(61, 1),
> > + PLL_PARAMS(62, 1),
> > + PLL_PARAMS(63, 1),
> > + PLL_PARAMS(64, 1),
> > + PLL_PARAMS(65, 1),
> > + PLL_PARAMS(66, 1),
> > + PLL_PARAMS(67, 1),
> > + PLL_PARAMS(68, 1),
> > { /* sentinel */ },
> > };
> >
> > @@ -203,7 +203,7 @@ static struct clk_regmap axg_gp0_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = axg_gp0_pll_rate_table,
> > + .table = axg_gp0_pll_params_table,
> > .init_regs = axg_gp0_init_regs,
> > .init_count = ARRAY_SIZE(axg_gp0_init_regs),
> > },
> > @@ -271,7 +271,7 @@ static struct clk_regmap axg_hifi_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = axg_gp0_pll_rate_table,
> > + .table = axg_gp0_pll_params_table,
> > .init_regs = axg_hifi_init_regs,
> > .init_count = ARRAY_SIZE(axg_hifi_init_regs),
> > .flags = CLK_MESON_PLL_ROUND_CLOSEST,
> > @@ -627,11 +627,10 @@ static struct clk_regmap axg_mpll3 = {
> > },
> > };
> >
> > -static const struct pll_rate_table axg_pcie_pll_rate_table[] = {
> > +static const struct pll_params_table axg_pcie_pll_params_table[] = {
> > {
> > - .rate = 1600000000,
> > - .m = 200,
> > - .n = 3,
> > + .m = 200,
> > + .n = 3,
> > },
> > { /* sentinel */ },
> > };
> > @@ -678,7 +677,7 @@ static struct clk_regmap axg_pcie_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = axg_pcie_pll_rate_table,
> > + .table = axg_pcie_pll_params_table,
> > .init_regs = axg_pcie_init_regs,
> > .init_count = ARRAY_SIZE(axg_pcie_init_regs),
> > },
> > diff --git a/drivers/clk/meson/clk-pll.c b/drivers/clk/meson/clk-pll.c
> > index 348a866f09eb..f5b5b3fabe3c 100644
> > --- a/drivers/clk/meson/clk-pll.c
> > +++ b/drivers/clk/meson/clk-pll.c
> > @@ -45,7 +45,7 @@ meson_clk_pll_data(struct clk_regmap *clk)
> > }
> >
> > static unsigned long __pll_params_to_rate(unsigned long parent_rate,
> > - const struct pll_rate_table *pllt,
> > + const struct pll_params_table *pllt,
> > u16 frac,
> > struct meson_clk_pll_data *pll)
> > {
> > @@ -66,7 +66,7 @@ static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
> > {
> > struct clk_regmap *clk = to_clk_regmap(hw);
> > struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
> > - struct pll_rate_table pllt;
> > + struct pll_params_table pllt;
> > u16 frac;
> >
> > pllt.n = meson_parm_read(clk->map, &pll->n);
> > @@ -81,7 +81,7 @@ static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
> >
> > static u16 __pll_params_with_frac(unsigned long rate,
> > unsigned long parent_rate,
> > - const struct pll_rate_table *pllt,
> > + const struct pll_params_table *pllt,
> > struct meson_clk_pll_data *pll)
> > {
> > u16 frac_max = (1 << pll->frac.width);
> > @@ -97,29 +97,50 @@ static u16 __pll_params_with_frac(unsigned long rate,
> > return min((u16)val, (u16)(frac_max - 1));
> > }
> >
> > -static const struct pll_rate_table *
> > +static bool meson_clk_pll_is_better(unsigned long rate,
> > + unsigned long best,
> > + unsigned long now,
> > + struct meson_clk_pll_data *pll)
> > +{
> > + if (!(pll->flags & CLK_MESON_PLL_ROUND_CLOSEST) ||
> > + MESON_PARM_APPLICABLE(&pll->frac)) {
> > + /* Round down */
> > + if (now < rate && best < now)
> > + return true;
> > + } else {
> > + /* Round Closest */
> > + if (abs(now - rate) < abs(best - rate))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
> > +
> > +static const struct pll_params_table *
> > meson_clk_get_pll_settings(unsigned long rate,
> > + unsigned long parent_rate,
> > struct meson_clk_pll_data *pll)
> > {
> > - const struct pll_rate_table *table = pll->table;
> > - unsigned int i = 0;
> > + const struct pll_params_table *table = pll->table;
> > + unsigned long best = 0, now = 0;
> > + unsigned int i, best_i = 0;
> >
> > if (!table)
> > return NULL;
> >
> > - /* Find the first table element exceeding rate */
> > - while (table[i].rate && table[i].rate <= rate)
> > - i++;
> > + for (i = 0; table[i].n; i++) {
> > + now = __pll_params_to_rate(parent_rate, &table[i], 0, pll);
> >
> > - if (i != 0) {
> > - if (MESON_PARM_APPLICABLE(&pll->frac) ||
> > - !(pll->flags & CLK_MESON_PLL_ROUND_CLOSEST) ||
> > - (abs(rate - table[i - 1].rate) <
> > - abs(rate - table[i].rate)))
> > - i--;
> > + /* If we get an exact match, don't bother any further */
> > + if (now == rate) {
> > + return &table[i];
> > + } else if (meson_clk_pll_is_better(rate, best, now, pll)) {
> > + best = now;
> > + best_i = i;
> > + }
> > }
> >
> > - return (struct pll_rate_table *)&table[i];
> > + return (struct pll_params_table *)&table[best_i];
> > }
> >
> > static long meson_clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> > @@ -127,16 +148,18 @@ 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 =
> > - meson_clk_get_pll_settings(rate, pll);
> > + const struct pll_params_table *pllt =
> > + meson_clk_get_pll_settings(rate, *parent_rate, pll);
> > + unsigned long round;
> > u16 frac;
> >
> > if (!pllt)
> > return meson_clk_pll_recalc_rate(hw, *parent_rate);
> >
> > - if (!MESON_PARM_APPLICABLE(&pll->frac)
> > - || rate == pllt->rate)
> > - return pllt->rate;
> > + round = __pll_params_to_rate(*parent_rate, pllt, 0, pll);
> > +
> > + if (!MESON_PARM_APPLICABLE(&pll->frac) || rate == round)
> > + return round;
> >
> > /*
> > * The rate provided by the setting is not an exact match, let's
> > @@ -214,7 +237,7 @@ static int meson_clk_pll_set_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_params_table *pllt;
> > unsigned int enabled;
> > unsigned long old_rate;
> > u16 frac = 0;
> > @@ -224,7 +247,7 @@ static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> >
> > old_rate = rate;
> >
> > - pllt = meson_clk_get_pll_settings(rate, pll);
> > + pllt = meson_clk_get_pll_settings(rate, parent_rate, pll);
> > if (!pllt)
> > return -EINVAL;
> >
> > diff --git a/drivers/clk/meson/clkc.h b/drivers/clk/meson/clkc.h
> > index a2245e857f70..6b96d55c047d 100644
> > --- a/drivers/clk/meson/clkc.h
> > +++ b/drivers/clk/meson/clkc.h
> > @@ -43,15 +43,13 @@ static inline void meson_parm_write(struct regmap *map, struct parm *p,
> > }
> >
> >
> > -struct pll_rate_table {
> > - unsigned long rate;
> > +struct pll_params_table {
> > u16 m;
> > u16 n;
> > };
> >
> > -#define PLL_RATE(_r, _m, _n) \
> > +#define PLL_PARAMS(_m, _n) \
> > { \
> > - .rate = (_r), \
> > .m = (_m), \
> > .n = (_n), \
> > }
> > @@ -67,7 +65,7 @@ struct meson_clk_pll_data {
> > struct parm rst;
> > const struct reg_sequence *init_regs;
> > unsigned int init_count;
> > - const struct pll_rate_table *table;
> > + const struct pll_params_table *table;
> > u8 flags;
> > };
> >
> > diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
> > index e2d94498f098..9ac03c7bfbaa 100644
> > --- a/drivers/clk/meson/gxbb.c
> > +++ b/drivers/clk/meson/gxbb.c
> > @@ -18,67 +18,67 @@
> >
> > static DEFINE_SPINLOCK(meson_clk_lock);
> >
> > -static const struct pll_rate_table gxbb_gp0_pll_rate_table[] = {
> > - PLL_RATE(768000000, 32, 1),
> > - PLL_RATE(792000000, 33, 1),
> > - PLL_RATE(816000000, 34, 1),
> > - PLL_RATE(840000000, 35, 1),
> > - PLL_RATE(864000000, 36, 1),
> > - PLL_RATE(888000000, 37, 1),
> > - PLL_RATE(912000000, 38, 1),
> > - PLL_RATE(936000000, 39, 1),
> > - PLL_RATE(960000000, 40, 1),
> > - PLL_RATE(984000000, 41, 1),
> > - PLL_RATE(1008000000, 42, 1),
> > - PLL_RATE(1032000000, 43, 1),
> > - PLL_RATE(1056000000, 44, 1),
> > - PLL_RATE(1080000000, 45, 1),
> > - PLL_RATE(1104000000, 46, 1),
> > - PLL_RATE(1128000000, 47, 1),
> > - PLL_RATE(1152000000, 48, 1),
> > - PLL_RATE(1176000000, 49, 1),
> > - PLL_RATE(1200000000, 50, 1),
> > - PLL_RATE(1224000000, 51, 1),
> > - PLL_RATE(1248000000, 52, 1),
> > - PLL_RATE(1272000000, 53, 1),
> > - PLL_RATE(1296000000, 54, 1),
> > - PLL_RATE(1320000000, 55, 1),
> > - PLL_RATE(1344000000, 56, 1),
> > - PLL_RATE(1368000000, 57, 1),
> > - PLL_RATE(1392000000, 58, 1),
> > - PLL_RATE(1416000000, 59, 1),
> > - PLL_RATE(1440000000, 60, 1),
> > - PLL_RATE(1464000000, 61, 1),
> > - PLL_RATE(1488000000, 62, 1),
> > +static const struct pll_params_table gxbb_gp0_pll_params_table[] = {
> > + PLL_PARAMS(32, 1),
> > + PLL_PARAMS(33, 1),
> > + PLL_PARAMS(34, 1),
> > + PLL_PARAMS(35, 1),
> > + PLL_PARAMS(36, 1),
> > + PLL_PARAMS(37, 1),
> > + PLL_PARAMS(38, 1),
> > + PLL_PARAMS(39, 1),
> > + PLL_PARAMS(40, 1),
> > + PLL_PARAMS(41, 1),
> > + PLL_PARAMS(42, 1),
> > + PLL_PARAMS(43, 1),
> > + PLL_PARAMS(44, 1),
> > + PLL_PARAMS(45, 1),
> > + PLL_PARAMS(46, 1),
> > + PLL_PARAMS(47, 1),
> > + PLL_PARAMS(48, 1),
> > + PLL_PARAMS(49, 1),
> > + PLL_PARAMS(50, 1),
> > + PLL_PARAMS(51, 1),
> > + PLL_PARAMS(52, 1),
> > + PLL_PARAMS(53, 1),
> > + PLL_PARAMS(54, 1),
> > + PLL_PARAMS(55, 1),
> > + PLL_PARAMS(56, 1),
> > + PLL_PARAMS(57, 1),
> > + PLL_PARAMS(58, 1),
> > + PLL_PARAMS(59, 1),
> > + PLL_PARAMS(60, 1),
> > + PLL_PARAMS(61, 1),
> > + PLL_PARAMS(62, 1),
> > { /* sentinel */ },
> > };
> >
> > -static const struct pll_rate_table gxl_gp0_pll_rate_table[] = {
> > - PLL_RATE(1008000000, 42, 1),
> > - PLL_RATE(1032000000, 43, 1),
> > - PLL_RATE(1056000000, 44, 1),
> > - PLL_RATE(1080000000, 45, 1),
> > - PLL_RATE(1104000000, 46, 1),
> > - PLL_RATE(1128000000, 47, 1),
> > - PLL_RATE(1152000000, 48, 1),
> > - PLL_RATE(1176000000, 49, 1),
> > - PLL_RATE(1200000000, 50, 1),
> > - PLL_RATE(1224000000, 51, 1),
> > - PLL_RATE(1248000000, 52, 1),
> > - PLL_RATE(1272000000, 53, 1),
> > - PLL_RATE(1296000000, 54, 1),
> > - PLL_RATE(1320000000, 55, 1),
> > - PLL_RATE(1344000000, 56, 1),
> > - PLL_RATE(1368000000, 57, 1),
> > - PLL_RATE(1392000000, 58, 1),
> > - PLL_RATE(1416000000, 59, 1),
> > - PLL_RATE(1440000000, 60, 1),
> > - PLL_RATE(1464000000, 61, 1),
> > - PLL_RATE(1488000000, 62, 1),
> > - PLL_RATE(1512000000, 63, 1),
> > - PLL_RATE(1536000000, 64, 1),
> > - PLL_RATE(1560000000, 65, 1),
> > - PLL_RATE(1584000000, 66, 1),
> > +static const struct pll_params_table gxl_gp0_pll_params_table[] = {
> > + PLL_PARAMS(42, 1),
> > + PLL_PARAMS(43, 1),
> > + PLL_PARAMS(44, 1),
> > + PLL_PARAMS(45, 1),
> > + PLL_PARAMS(46, 1),
> > + PLL_PARAMS(47, 1),
> > + PLL_PARAMS(48, 1),
> > + PLL_PARAMS(49, 1),
> > + PLL_PARAMS(50, 1),
> > + PLL_PARAMS(51, 1),
> > + PLL_PARAMS(52, 1),
> > + PLL_PARAMS(53, 1),
> > + PLL_PARAMS(54, 1),
> > + PLL_PARAMS(55, 1),
> > + PLL_PARAMS(56, 1),
> > + PLL_PARAMS(57, 1),
> > + PLL_PARAMS(58, 1),
> > + PLL_PARAMS(59, 1),
> > + PLL_PARAMS(60, 1),
> > + PLL_PARAMS(61, 1),
> > + PLL_PARAMS(62, 1),
> > + PLL_PARAMS(63, 1),
> > + PLL_PARAMS(64, 1),
> > + PLL_PARAMS(65, 1),
> > + PLL_PARAMS(66, 1),
> > { /* sentinel */ },
> > };
> >
> > @@ -374,7 +374,7 @@ static struct clk_regmap gxbb_gp0_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = gxbb_gp0_pll_rate_table,
> > + .table = gxbb_gp0_pll_params_table,
> > .init_regs = gxbb_gp0_init_regs,
> > .init_count = ARRAY_SIZE(gxbb_gp0_init_regs),
> > },
> > @@ -427,7 +427,7 @@ static struct clk_regmap gxl_gp0_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = gxl_gp0_pll_rate_table,
> > + .table = gxl_gp0_pll_params_table,
> > .init_regs = gxl_gp0_init_regs,
> > .init_count = ARRAY_SIZE(gxl_gp0_init_regs),
> > },
> > diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> > index 17bcf0be56ba..30ae849ff53f 100644
> > --- a/drivers/clk/meson/meson8b.c
> > +++ b/drivers/clk/meson/meson8b.c
> > @@ -29,22 +29,22 @@ struct meson8b_clk_reset {
> > void __iomem *base;
> > };
> >
> > -static const struct pll_rate_table sys_pll_rate_table[] = {
> > - PLL_RATE(1200000000, 50, 1),
> > - PLL_RATE(1224000000, 51, 1),
> > - PLL_RATE(1248000000, 52, 1),
> > - PLL_RATE(1272000000, 53, 1),
> > - PLL_RATE(1296000000, 54, 1),
> > - PLL_RATE(1320000000, 55, 1),
> > - PLL_RATE(1344000000, 56, 1),
> > - PLL_RATE(1368000000, 57, 1),
> > - PLL_RATE(1392000000, 58, 1),
> > - PLL_RATE(1416000000, 59, 1),
> > - PLL_RATE(1440000000, 60, 1),
> > - PLL_RATE(1464000000, 61, 1),
> > - PLL_RATE(1488000000, 62, 1),
> > - PLL_RATE(1512000000, 63, 1),
> > - PLL_RATE(1536000000, 64, 1),
> > +static const struct pll_params_table sys_pll_params_table[] = {
> > + PLL_PARAMS(50, 1),
> > + PLL_PARAMS(51, 1),
> > + PLL_PARAMS(52, 1),
> > + PLL_PARAMS(53, 1),
> > + PLL_PARAMS(54, 1),
> > + PLL_PARAMS(55, 1),
> > + PLL_PARAMS(56, 1),
> > + PLL_PARAMS(57, 1),
> > + PLL_PARAMS(58, 1),
> > + PLL_PARAMS(59, 1),
> > + PLL_PARAMS(60, 1),
> > + PLL_PARAMS(61, 1),
> > + PLL_PARAMS(62, 1),
> > + PLL_PARAMS(63, 1),
> > + PLL_PARAMS(64, 1),
> > { /* sentinel */ },
> > };
> >
> > @@ -195,7 +195,7 @@ static struct clk_regmap meson8b_sys_pll_dco = {
> > .shift = 29,
> > .width = 1,
> > },
> > - .table = sys_pll_rate_table,
> > + .table = sys_pll_params_table,
> > },
> > .hw.init = &(struct clk_init_data){
> > .name = "sys_pll_dco",
> >
>
> We could even add ranges instead of table when we know the PLL supports a well-known continuous dividers range.
I had a look at the sys_pll settings on Meson8b, here's what
Meson8/Meson8b/Meson8m2 support for sys_pll:
- 50..74
- 76
- 78
- 80
- 82
- 84
- 86
- 88
- 90
- 92
- 94
- 96
- 98

(I'm providing this info because it may help finding a decision
whether ranges are good or not. I have no preference)


Regards
Martin


[0] https://github.com/endlessm/linux-meson/blob/master/arch/arm/mach-meson8/clock.c#L140