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SubjectRe: [linux-sunxi] [PATCH 1/2] clk: sunxi-ng: Support fixed post-dividers on MP style clocks
On Tue, Dec 5, 2017 at 7:18 AM, André Przywara <andre.przywara@arm.com> wrote:
> Hi Chen-Yu,
>
> On 04/12/17 05:19, Chen-Yu Tsai wrote:
>> On the A64, the MMC module clocks are fixed in the new timing mode,
>> i.e. they do not have a bit to select the mode. These clocks have
>> a 2x divider somewhere between the clock and the MMC module.
>>
>> To be consistent with other SoCs supporting the new timing mode,
>> we model the 2x divider as a fixed post-divider on the MMC module
>> clocks.
>>
>> To do this, we first add fixed post-divider to the MP style clocks,
>> which the MMC module clocks are.
>>
>> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
>> ---
>> drivers/clk/sunxi-ng/ccu_mp.c | 20 ++++++++++++++++++--
>> drivers/clk/sunxi-ng/ccu_mp.h | 24 ++++++++++++++++++++++++
>> 2 files changed, 42 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clk/sunxi-ng/ccu_mp.c b/drivers/clk/sunxi-ng/ccu_mp.c
>> index 688855e7dc8c..5d0af4051737 100644
>> --- a/drivers/clk/sunxi-ng/ccu_mp.c
>> +++ b/drivers/clk/sunxi-ng/ccu_mp.c
>> @@ -50,12 +50,19 @@ static unsigned long ccu_mp_round_rate(struct ccu_mux_internal *mux,
>> unsigned int max_m, max_p;
>> unsigned int m, p;
>>
>> + if (cmp->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> + rate *= cmp->fixed_post_div;
>
> Can't you just initialise fixed_post_div to 1 normally and save the
> CCU_FEATURE_FIXED_POSTDIV?

I'll refer to Maxime about this. The feature flag was there from day
one. We only started to implement support for it later on. I'm not
sure if there was a reason to add them as feature flags, instead of
a field that defaults to something (0 even).

Otherwise it's a reasonable change. And we probably don't have to
do a wholesale change for the other clocks in one go. Incidentally
I have a A83T audio series that also adds post-dividers for another
clock type. I'll wait for a conclusion on this end before posting
it.

>
>> +
>> max_m = cmp->m.max ?: 1 << cmp->m.width;
>> max_p = cmp->p.max ?: 1 << ((1 << cmp->p.width) - 1);
>>
>> ccu_mp_find_best(*parent_rate, rate, max_m, max_p, &m, &p);
>> + rate = *parent_rate / p / m;
>> +
>> + if (cmp->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> + rate /= cmp->fixed_post_div;
>>
>> - return *parent_rate / p / m;
>> + return rate;
>> }
>>
>> static void ccu_mp_disable(struct clk_hw *hw)
>> @@ -83,6 +90,7 @@ static unsigned long ccu_mp_recalc_rate(struct clk_hw *hw,
>> unsigned long parent_rate)
>> {
>> struct ccu_mp *cmp = hw_to_ccu_mp(hw);
>> + unsigned long rate;
>> unsigned int m, p;
>> u32 reg;
>>
>> @@ -101,7 +109,11 @@ static unsigned long ccu_mp_recalc_rate(struct clk_hw *hw,
>> p = reg >> cmp->p.shift;
>> p &= (1 << cmp->p.width) - 1;
>>
>> - return (parent_rate >> p) / m;
>> + rate = (parent_rate >> p) / m;
>> + if (cmp->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> + rate /= cmp->fixed_post_div;
>> +
>> + return rate;
>> }
>>
>> static int ccu_mp_determine_rate(struct clk_hw *hw,
>> @@ -129,6 +141,10 @@ static int ccu_mp_set_rate(struct clk_hw *hw, unsigned long rate,
>> max_m = cmp->m.max ?: 1 << cmp->m.width;
>> max_p = cmp->p.max ?: 1 << ((1 << cmp->p.width) - 1);
>>
>> + /* Adjust target rate according to post-dividers */
>> + if (cmp->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> + rate = rate * cmp->fixed_post_div;
>> +
>> ccu_mp_find_best(parent_rate, rate, max_m, max_p, &m, &p);
>>
>> spin_lock_irqsave(cmp->common.lock, flags);
>> diff --git a/drivers/clk/sunxi-ng/ccu_mp.h b/drivers/clk/sunxi-ng/ccu_mp.h
>> index aaef11d747ea..5107635e61de 100644
>> --- a/drivers/clk/sunxi-ng/ccu_mp.h
>> +++ b/drivers/clk/sunxi-ng/ccu_mp.h
>> @@ -33,9 +33,33 @@ struct ccu_mp {
>> struct ccu_div_internal m;
>> struct ccu_div_internal p;
>> struct ccu_mux_internal mux;
>> +
>> + unsigned int fixed_post_div;
>> +
>> struct ccu_common common;
>> };
>>
>> +#define SUNXI_CCU_MP_WITH_MUX_GATE_POSTDIV(_struct, _name, _parents, _reg, \
>> + _mshift, _mwidth, \
>> + _pshift, _pwidth, \
>> + _muxshift, _muxwidth, \
>> + _gate, _postdiv, _flags) \
>> + struct ccu_mp _struct = { \
>> + .enable = _gate, \
>> + .m = _SUNXI_CCU_DIV(_mshift, _mwidth), \
>> + .p = _SUNXI_CCU_DIV(_pshift, _pwidth), \
>> + .mux = _SUNXI_CCU_MUX(_muxshift, _muxwidth), \
>> + .fixed_post_div = _postdiv, \
>> + .common = { \
>> + .reg = _reg, \
>> + .features = CCU_FEATURE_FIXED_POSTDIV, \
>> + .hw.init = CLK_HW_INIT_PARENTS(_name, \
>> + _parents, \
>> + &ccu_mp_ops, \
>> + _flags), \
>> + } \
>> + }
>> +
>
> This looks suspiciously like a copy of the macro below. What about you
> define the one below as a special case of this new one above?

Correct. But you can't unset the feature flag. So a copy is needed.

> Should be even more straightforward with defaulting postdiv to 1 and
> loosing the feature flags.

See above about the feature flag.

ChenYu

>
> Cheers,
> Andre.
>
>> #define SUNXI_CCU_MP_WITH_MUX_GATE(_struct, _name, _parents, _reg, \
>> _mshift, _mwidth, \
>> _pshift, _pwidth, \
>>
>

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