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SubjectRe: [linux-sunxi] Re: [PATCH v6 1/6] clk: sunxi-ng: div: Add support for fixed post-divider
在 2017-08-12 12:13,Chen-Yu Tsai 写道:
> On Sat, Aug 12, 2017 at 11:07 AM, <icenowy@aosc.io> wrote:
>> 在 2017-07-17 16:52,Maxime Ripard 写道:
>>>
>>> On Fri, Jul 14, 2017 at 05:49:23PM +0300, Priit Laes wrote:
>>>>
>>>> SATA clock on sun4i/sun7i is of type (parent) / M / 6 where
>>>> 6 is fixed post-divider.
>>>>
>>>> Signed-off-by: Priit Laes <plaes@plaes.org>
>>>> ---
>>>> drivers/clk/sunxi-ng/ccu_div.c | 15 +++++++++++++--
>>>> drivers/clk/sunxi-ng/ccu_div.h | 3 ++-
>>>> 2 files changed, 15 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/clk/sunxi-ng/ccu_div.c
>>>> b/drivers/clk/sunxi-ng/ccu_div.c
>>>> index c0e5c10..744502a 100644
>>>> --- a/drivers/clk/sunxi-ng/ccu_div.c
>>>> +++ b/drivers/clk/sunxi-ng/ccu_div.c
>>>> @@ -21,6 +21,9 @@ static unsigned long ccu_div_round_rate(struct
>>>> ccu_mux_internal *mux,
>>>> {
>>>> struct ccu_div *cd = data;
>>>>
>>>> + if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
>>>> + rate *= cd->fixed_post_div;
>>>> +
>>>> return divider_round_rate_parent(&cd->common.hw, parent,
>>>> rate, parent_rate,
>>>> cd->div.table,
>>>> cd->div.width,
>>>
>>>
>>>
>>> You still haven't addressed the biggest issue with this patch, see:
>>> https://patchwork.kernel.org/patch/9825565/
>>
>>
>> I think he has already did the changes suggested in the review.
>
> Nope. Only half of it is fixed. First you "unapply" the post-divider,
> i.e. multiply the rate by the divider. Then you pass it to
> divider_round_rate_parent. You still have to reapply the divider
> to the result. This last part is missing. This means the clock
> rate returned by ccu_div_round_rate is going to be off.
>
> Instead the return statement should be
>
> return divider_round_rate_parent(...) / cd->fixed_post_div

Oh, got it by reading other CCU clock types that has fixed postdiv.

Thanks!

>
> ChenYu
>
>>
>> (P.S. during developing R40 CCU driver I found that pll-periph0-sata
>> also needs this patch, so I'm rechecking it)
>>
>>>
>>> Maxime
>>>
>>> _______________________________________________
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>>
>>
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