linux-kernel - Re: [PATCH v2 19/48] opp: Fix adding OPP entries in a wrong order if rate is unavailable

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Date:   Tue, 22 Dec 2020 22:19:26 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 19/48] opp: Fix adding OPP entries in a wrong order if
 rate is unavailable

22.12.2020 12:12, Viresh Kumar пишет:
> On 17-12-20, 21:06, Dmitry Osipenko wrote:
>> Fix adding OPP entries in a wrong (opposite) order if OPP rate is
>> unavailable. The OPP comparison is erroneously skipped if OPP rate is
>> missing, thus OPPs are left unsorted.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/opp/core.c | 23 ++++++++++++-----------
>>  drivers/opp/opp.h  |  2 +-
>>  2 files changed, 13 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>> index 34f7e530d941..5c7f130a8de2 100644
>> --- a/drivers/opp/core.c
>> +++ b/drivers/opp/core.c
>> @@ -1531,9 +1531,10 @@ static bool _opp_supported_by_regulators(struct dev_pm_opp *opp,
>>  	return true;
>>  }
>>  
>> -int _opp_compare_key(struct dev_pm_opp *opp1, struct dev_pm_opp *opp2)
>> +int _opp_compare_key(struct dev_pm_opp *opp1, struct dev_pm_opp *opp2,
>> +		     bool rate_not_available)
>>  {
>> -	if (opp1->rate != opp2->rate)
>> +	if (!rate_not_available && opp1->rate != opp2->rate)
> 
> rate will be 0 for both the OPPs here if rate_not_available is true and so this
> change shouldn't be required.

The rate_not_available is negated in the condition. This change is
required because both rates are 0 and then we should proceed to the
levels comparison.

I guess it's not clear by looking at this patch, please see a full
version of the function:

int _opp_compare_key(struct dev_pm_opp *opp1, struct dev_pm_opp *opp2,
         bool rate_not_available)
{
  if (!rate_not_available && opp1->rate != opp2->rate)
    return opp1->rate < opp2->rate ? -1 : 1;
  if (opp1->bandwidth && opp2->bandwidth &&
      opp1->bandwidth[0].peak != opp2->bandwidth[0].peak)
    return opp1->bandwidth[0].peak < opp2->bandwidth[0].peak ? -1 : 1;
  if (opp1->level != opp2->level)
    return opp1->level < opp2->level ? -1 : 1;
  return 0;
}

Perhaps we could check whether opp1->rate=0, like it's done for the
opp1->bandwidth. I'll consider this variant for v3, thanks.