linux-kernel - Re: [PATCH v5 02/11] clk: sunxi-ng: nkm: consider alternative parent rates when determining rate

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Date:   Sun, 06 Aug 2023 15:57:00 +0200
From:   Frank Oltmanns <frank@...manns.dev>
To:     Jernej Škrabec <jernej.skrabec@...il.com>
Cc:     Maxime Ripard <mripard@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        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 v5 02/11] clk: sunxi-ng: nkm: consider alternative
 parent rates when determining rate


On 2023-08-06 at 15:32:29 +0200, Jernej Škrabec <jernej.skrabec@...il.com> wrote:
> Dne nedelja, 06. avgust 2023 ob 15:06:47 CEST je Frank Oltmanns napisal(a):
>> In case the CLK_SET_RATE_PARENT flag is set, consider using a different
>> parent rate when determining a new rate.
>>
>> To find the best match for the requested rate, perform the following
>> steps for each NKM combination:
>>  - calculate the optimal parent rate,
>>  - find the best parent rate that the parent clock actually supports
>>  - use that parent rate to calculate the effective rate.
>>
>> In case the clk does not support setting the parent rate, use the same
>> algorithm as before.
>>
>> Acked-by: Maxime Ripard <mripard@...nel.org>
>> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
>> ---
>>  drivers/clk/sunxi-ng/ccu_nkm.c | 45
>> +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 44
>> insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
>> index f267142e58b3..ea1b77e9b57f 100644
>> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
>> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
>> @@ -6,6 +6,7 @@
>>
>>  #include <linux/clk-provider.h>
>>  #include <linux/io.h>
>> +#include <linux/math.h>
>
> Why do you need above include?

It's not needed. It's a leftover from an earlier version. I'll remove it
in v6.

Thank you for your review,
  Frank

>
> Best regards,
> Jernej
>
>>
>>  #include "ccu_gate.h"
>>  #include "ccu_nkm.h"
>> @@ -16,6 +17,45 @@ struct _ccu_nkm {
>>  	unsigned long	m, min_m, max_m;
>>  };
>>
>> +static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw
>> *parent_hw, +
>        unsigned long *parent, unsigned long rate,
>> +
> struct _ccu_nkm *nkm)
>> +{
>> +	unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent
> =
>> *parent; +	unsigned long best_n = 0, best_k = 0, best_m = 0;
>> +	unsigned long _n, _k, _m;
>> +
>> +	for (_k = nkm->min_k; _k <= nkm->max_k; _k++) {
>> +		for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
>> +			for (_m = nkm->min_m; _m <= nkm->max_m; _m++)
> {
>> +				unsigned long tmp_rate;
>> +
>> +				tmp_parent =
> clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));
>> +
>> +				tmp_rate = tmp_parent * _n * _k /
> _m;
>> +				if (tmp_rate > rate)
>> +					continue;
>> +
>> +				if ((rate - tmp_rate) < (rate -
> best_rate)) {
>> +					best_rate = tmp_rate;
>> +					best_parent_rate =
> tmp_parent;
>> +					best_n = _n;
>> +					best_k = _k;
>> +					best_m = _m;
>> +				}
>> +			}
>> +		}
>> +	}
>> +
>> +	nkm->n = best_n;
>> +	nkm->k = best_k;
>> +	nkm->m = best_m;
>> +
>> +	*parent = best_parent_rate;
>> +
>> +	return best_rate;
>> +}
>> +
>>  static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long
>> rate, struct _ccu_nkm *nkm)
>>  {
>> @@ -124,7 +164,10 @@ static unsigned long ccu_nkm_round_rate(struct
>> ccu_mux_internal *mux, if (nkm->common.features &
>> CCU_FEATURE_FIXED_POSTDIV)
>>  		rate *= nkm->fixed_post_div;
>>
>> -	rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm);
>> +	if (!clk_hw_can_set_rate_parent(&nkm->common.hw))
>> +		rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm);
>> +	else
>> +		rate = ccu_nkm_find_best_with_parent_adj(parent_hw,
> parent_rate, rate,
>> &_nkm);
>>
>>  	if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
>>  		rate /= nkm->fixed_post_div;