linux-kernel - Re: [PATCH v2 15/48] opp: Support set_opp() customization without requiring to use regulators

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Message-ID: <ea025b0f-bb2a-d075-4c8e-45831fa9cd93@gmail.com>
Date:   Wed, 23 Dec 2020 23:38:44 +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 15/48] opp: Support set_opp() customization without
 requiring to use regulators

23.12.2020 09:01, Viresh Kumar пишет:
> On 17-12-20, 21:06, Dmitry Osipenko wrote:
>> Support set_opp() customization without requiring to use regulators. This
>> is needed by drivers which want to use dev_pm_opp_set_rate() for changing
>> rates of a multiple clocks and don't need to touch regulator.
>>
>> One example is NVIDIA Tegra30/114 SoCs which have two sibling 3D hardware
>> units which should be use to the same clock rate, meanwhile voltage
>> scaling is done using a power domain. In this case OPP table doesn't have
>> a regulator, causing a NULL dereference in _set_opp_custom().
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/opp/core.c | 16 ++++++++++++----
>>  1 file changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>> index 3d02fe33630b..625dae7a5ecb 100644
>> --- a/drivers/opp/core.c
>> +++ b/drivers/opp/core.c
>> @@ -828,17 +828,25 @@ static int _set_opp_custom(const struct opp_table *opp_table,
>>  			   struct dev_pm_opp_supply *old_supply,
>>  			   struct dev_pm_opp_supply *new_supply)
>>  {
>> -	struct dev_pm_set_opp_data *data;
>> +	struct dev_pm_set_opp_data *data, tmp_data;
>> +	unsigned int regulator_count;
>>  	int size;
>>  
>> -	data = opp_table->set_opp_data;
>> +	if (opp_table->set_opp_data) {
>> +		data = opp_table->set_opp_data;
>> +		regulator_count = opp_table->regulator_count;
>> +	} else {
>> +		data = &tmp_data;
>> +		regulator_count = 0;
>> +	}
>> +
> 
> We should use the same structure, you can add some checks but not replace the
> structure altogether.

Well, there is no "same structure", the opp_table->set_opp_data is NULL
there.

I can re-write it like this if it looks better to you:

static int _set_opp_custom(...)
{
	struct dev_pm_set_opp_data *data;
	unsigned int regulator_count;
	int size;

+	if (!opp_table->set_opp_data) {
+		struct dev_pm_set_opp_data freq_data = {};
+
+		freq_data.dev = dev;
+		freq_data.clk = opp_table->clk;
+		freq_data.new_opp.rate = freq;
+		freq_data.old_opp.rate = old_freq;
+
+		return opp_table->set_opp(&freq_data);
+	}