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

[Dmitry Osipenko]

22.12.2020 12:01, 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@xxxxxxxxx>
>> ---
>>  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;
>> +	}
>> +
>>  	data->regulators = opp_table->regulators;
>> -	data->regulator_count = opp_table->regulator_count;
>> +	data->regulator_count = regulator_count;
>>  	data->clk = opp_table->clk;
>>  	data->dev = dev;
>>  
>>  	data->old_opp.rate = old_freq;
>> -	size = sizeof(*old_supply) * opp_table->regulator_count;
>> +	size = sizeof(*old_supply) * regulator_count;
>>  	if (!old_supply)
>>  		memset(data->old_opp.supplies, 0, size);
>>  	else
> 
> I don't see you making use of this in this patchset. How did you get this to
> crash ?
> 

Please see patch 38 where 3d driver makes use of
devm_pm_opp_register_set_opp_helper().

The opp_table->set_opp_data=NULL and opp_table->regulator_count=-1 if
OPP table doesn't use a regulator, hence the crash happens.