linux-kernel - Re: [PATCH] opp: of: Allow lazy-linking of required-opps to non genpd

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Date:   Wed, 16 Jun 2021 14:39:45 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Hsin-Yi Wang <hsinyi@...omium.org>,
        "Viresh Kumar )" <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "andrew-sh . cheng" <andrew-sh.cheng@...iatek.com>
Subject: Re: [PATCH] opp: of: Allow lazy-linking of required-opps to non genpd

On 16-06-21, 17:47, Chanwoo Choi wrote:
> On 6/16/21 4:55 PM, Viresh Kumar wrote:
> > On 16-06-21, 13:33, Hsin-Yi Wang wrote:
> >> Don't limit required_opp_table to genpd only. One possible use case is
> >> cpufreq based devfreq governor, which can use required-opps property to
> >> derive devfreq from cpufreq.
> >>
> >> Suggested-by: Chanwoo Choi <cw00.choi@...sung.com>
> >> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> >> ---
> >> This is tested with the non genpd case mt8183-cci with passive
> >> governor[1].
> >> [1] https://patchwork.kernel.org/project/linux-mediatek/patch/1616499241-4906-2-git-send-email-andrew-sh.cheng@mediatek.com/
> >> ---
> >>  drivers/opp/of.c | 20 +-------------------
> >>  1 file changed, 1 insertion(+), 19 deletions(-)
> >>
> >> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> >> index aa75a1caf08a3..9573facce53a5 100644
> >> --- a/drivers/opp/of.c
> >> +++ b/drivers/opp/of.c
> >> @@ -201,17 +201,6 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
> >>  			lazy = true;
> >>  			continue;
> >>  		}
> >> -
> >> -		/*
> >> -		 * We only support genpd's OPPs in the "required-opps" for now,
> >> -		 * as we don't know how much about other cases. Error out if the
> >> -		 * required OPP doesn't belong to a genpd.
> >> -		 */
> >> -		if (!required_opp_tables[i]->is_genpd) {
> >> -			dev_err(dev, "required-opp doesn't belong to genpd: %pOF\n",
> >> -				required_np);
> >> -			goto free_required_tables;
> >> -		}
> >>  	}
> >>  
> >>  	/* Let's do the linking later on */
> >> @@ -379,13 +368,6 @@ static void lazy_link_required_opp_table(struct opp_table *new_table)
> >>  	struct dev_pm_opp *opp;
> >>  	int i, ret;
> >>  
> >> -	/*
> >> -	 * We only support genpd's OPPs in the "required-opps" for now,
> >> -	 * as we don't know much about other cases.
> >> -	 */
> >> -	if (!new_table->is_genpd)
> >> -		return;
> >> -
> >>  	mutex_lock(&opp_table_lock);
> >>  
> >>  	list_for_each_entry_safe(opp_table, temp, &lazy_opp_tables, lazy) {
> >> @@ -873,7 +855,7 @@ static struct dev_pm_opp *_opp_add_static_v2(struct opp_table *opp_table,
> >>  		return ERR_PTR(-ENOMEM);
> >>  
> >>  	ret = _read_opp_key(new_opp, opp_table, np, &rate_not_available);
> >> -	if (ret < 0 && !opp_table->is_genpd) {
> >> +	if (ret < 0) {
> >>  		dev_err(dev, "%s: opp key field not found\n", __func__);
> >>  		goto free_opp;
> >>  	}
> > 
> > Plus this and few changes to commit log.
> > 
> > diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> > index e366218d6736..b335c077f215 100644
> > --- a/drivers/opp/core.c
> > +++ b/drivers/opp/core.c
> > @@ -893,6 +893,16 @@ static int _set_required_opps(struct device *dev,
> >         if (!required_opp_tables)
> >                 return 0;
> >  
> > +       /*
> > +        * We only support genpd's OPPs in the "required-opps" for now, as we
> > +        * don't know much about other use cases. Error out if the required OPP
> > +        * doesn't belong to a genpd.
> > +        */
> > +       if (unlikely(!required_opp_tables[0]->is_genpd)) {
> > +               dev_err(dev, "required-opps don't belong to a genpd\n");
> > +               return -ENOENT;
> > +       }
> > +
> 
> If you add this checking statement, I think that 
> when using dev_pm_opp_set_rate with required-opp property, it will be failed.

Yes, that is exactly what I am trying to do here. Hsin already
confirmed that you guys won't use this API, isn't ?

The point here is that the _set_required_opps() function only updates
the performance state of genpds today. So it won't work for you guys
anyway.

-- 
viresh