linux-kernel - Re: [PATCH v4 08/11] clk: sunxi-ng: nkm: Support finding closest rate

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Date:   Sun, 23 Jul 2023 09:25:10 +0200
From:   Frank Oltmanns <frank@...manns.dev>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Andre Przywara <andre.przywara@....com>,
        Roman Beranek <me@...y.cz>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 08/11] clk: sunxi-ng: nkm: Support finding closest rate

Hi Maxime,

On 2023-07-17 at 16:14:58 +0200, Maxime Ripard <mripard@...nel.org> wrote:
> [[PGP Signed Part:Undecided]]
> On Mon, Jul 17, 2023 at 03:34:32PM +0200, Frank Oltmanns wrote:
>> When finding the best rate for a NKM clock, consider rates that are
>> higher than the requested rate, if the CCU_FEATURE_CLOSEST_RATE flag is
>> set by using the helper function ccu_is_better_rate().
>>
>> Accommodate ccu_mux_helper_determine_rate to this change.
>>
>> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
>> ---
>>  drivers/clk/sunxi-ng/ccu_mux.c |  2 +-
>>  drivers/clk/sunxi-ng/ccu_nkm.c | 18 ++++++++----------
>>  2 files changed, 9 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c
>> index 1d557e323169..3ca695439620 100644
>> --- a/drivers/clk/sunxi-ng/ccu_mux.c
>> +++ b/drivers/clk/sunxi-ng/ccu_mux.c
>> @@ -139,7 +139,7 @@ int ccu_mux_helper_determine_rate(struct ccu_common *common,
>>  			goto out;
>>  		}
>>
>> -		if ((req->rate - tmp_rate) < (req->rate - best_rate)) {
>> +		if (ccu_is_better_rate(common, req->rate, tmp_rate, best_rate)) {
>>  			best_rate = tmp_rate;
>>  			best_parent_rate = parent_rate;
>>  			best_parent = parent;
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
>> index 793160bc2d47..5439b9351cd7 100644
>> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
>> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
>> @@ -39,6 +39,7 @@ static unsigned long ccu_nkm_optimal_parent_rate(unsigned long rate, unsigned lo
>>  }
>>
>>  static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struct _ccu_nkm *nkm,
>> +						       struct ccu_common *common,
>>  						       unsigned long *parent, unsigned long rate)
>>  {
>>  	unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent = *parent;
>> @@ -54,10 +55,8 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struc
>>  				tmp_parent = clk_hw_round_rate(phw, tmp_parent);
>>
>>  				tmp_rate = tmp_parent * _n * _k / _m;
>> -				if (tmp_rate > rate)
>> -					continue;
>>
>> -				if ((rate - tmp_rate) < (rate - best_rate)) {
>> +				if (ccu_is_better_rate(common, rate, tmp_rate, best_rate)) {
>>  					best_rate = tmp_rate;
>>  					best_parent_rate = tmp_parent;
>>  					best_n = _n;
>> @@ -78,7 +77,7 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *phw, struc
>>  }
>>
>>  static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
>> -				       struct _ccu_nkm *nkm)
>> +				       struct _ccu_nkm *nkm, struct ccu_common *common)
>
> Same comment than on patch 7, common should be first in those two functions.
>

Ok, I wasn't sure what your expectation is for existing functions. For
ccu_find_best_with_parent_adj the order is:
  1. *phw
  2. *nkm
  3. *common
  4. *parent
  5. rate

We don't have the parent hw in ccu_nkm_find_best. The order prior to
this patch is:
  1. parent
  2. rate
  3. *nkm

We need to add *common to that, so I could add it to the beginning as
per your suggestion:
  1. *common
  2. parent
  3. rate
  4. *nkm

I could also pull *nkm to the beginning (similar to the parent_adj
version):
  4. *nkm
  1. *common
  2. parent
  3. rate

Thanks for your feedback,
  Frank

>
> Once fixed,
> Acked-by: Maxime Ripard <mripard@...nel.org>
>
> Maxime
>
> [[End of PGP Signed Part]]