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

Viresh Kumar
2021-08-18T04:31:39Z

On 18-08-21, 07:12, Dmitry Osipenko wrote:
> 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.

But the OPPs should already be initialized as someone must have called
opp-set-rate earlier ? Why do this from resume and not probe ?

--
viresh