linux-kernel - Re: [PATCH] clk: at91: generated: consider range when calculating best rate

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Message-ID: <e18eb810-e437-6a19-26ec-1f0daedaaf5f@microchip.com>
Date:   Tue, 26 Apr 2022 07:24:15 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <sboyd@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <mturquette@...libre.com>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Claudiu.Beznea@...rochip.com>
Subject: Re: [PATCH] clk: at91: generated: consider range when calculating
 best rate

On 22.04.2022 04:12, Stephen Boyd wrote:
> Quoting Codrin Ciubotariu (2022-04-13 00:13:18)
>> clk_generated_best_diff() helps in finding the parent and the divisor to
>> compute a rate closest to the required one. However, it doesn't take into
>> account the request's range for the new rate. Make sure the new rate
>> is within the required range.
>>
>> Fixes: 8a8f4bf0c480 ("clk: at91: clk-generated: create function to find best_diff")
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
>> ---
> 
> Is this fixing anything real or it's just a thing that you noticed and
> sent a patch to fix?

It fixes the clk_set_min/max_rate() calls to a generated clock. Do you 
want me to add this fact in the commit description?

> 
>>   drivers/clk/at91/clk-generated.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
>> index 23cc8297ec4c..d429ba52a719 100644
>> --- a/drivers/clk/at91/clk-generated.c
>> +++ b/drivers/clk/at91/clk-generated.c
>> @@ -117,6 +117,10 @@ static void clk_generated_best_diff(struct clk_rate_request *req,
>>                  tmp_rate = parent_rate;
>>          else
>>                  tmp_rate = parent_rate / div;
>> +
>> +       if (tmp_rate < req->min_rate || tmp_rate > req->max_rate)
>> +               return;
>> +
>>          tmp_diff = abs(req->rate - tmp_rate);
>>
>>          if (*best_diff < 0 || *best_diff >= tmp_diff) {