[PATCH v8 01/34] opp: Add dev_pm_opp_sync() helper

[Dmitry Osipenko]

18.08.2021 06:55, Viresh Kumar пишет:
> On 17-08-21, 18:49, Dmitry Osipenko wrote:
>> 17.08.2021 10:55, Viresh Kumar пишет:
>> ...
>>>> +int dev_pm_opp_sync(struct device *dev)
>>>> +{
>>>> +	struct opp_table *opp_table;
>>>> +	struct dev_pm_opp *opp;
>>>> +	int ret = 0;
>>>> +
>>>> +	/* Device may not have OPP table */
>>>> +	opp_table = _find_opp_table(dev);
>>>> +	if (IS_ERR(opp_table))
>>>> +		return 0;
>>>> +
>>>> +	if (!_get_opp_count(opp_table))
>>>> +		goto put_table;
>>>> +
>>>> +	opp = _find_current_opp(dev, opp_table);
>>>> +	ret = _set_opp(dev, opp_table, opp, opp->rate);
>>>
>>> And I am not sure how this will end up working, since new OPP will be
>>> equal to old one. Since I see you call this from resume() at many
>>> places.
>>
>> Initially OPP table is "uninitialized" and opp_table->enabled=false,
>> hence the first sync always works even if OPP is equal to old one. Once
>> OPP has been synced, all further syncs are NO-OPs, hence it doesn't
>> matter how many times syncing is called.
>>
>> https://elixir.bootlin.com/linux/v5.14-rc6/source/drivers/opp/core.c#L1012
> 
> Right, but how will this work from Resume ? Won't that be a no-op ?

The first resume initializes the OPP state on sync, all further syncs on
resume are no-ops.