linux-kernel - Re: [PATCH 1/2] OPP: pstate is only valid for genpd OPP tables

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Date:   Fri, 16 Jun 2023 11:48:30 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] OPP: pstate is only valid for genpd OPP tables

On 15-06-23, 18:35, Bjorn Andersson wrote:
> On Wed, Jun 14, 2023 at 04:07:25PM +0530, Viresh Kumar wrote:
> > It is not very clear right now that the `pstate` field is only valid for
> > genpd OPP tables and not consumer tables. And there is no checking for
> > the same at various places.
> > 
> > Add checks in place to verify that and make it clear to the reader.
> > 
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> > ---
> >  drivers/opp/core.c    | 18 ++++++++++++++++--
> >  drivers/opp/debugfs.c |  4 +++-
> >  drivers/opp/of.c      |  6 ++++++
> >  3 files changed, 25 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> [..]
> > @@ -2686,6 +2694,12 @@ int dev_pm_opp_xlate_performance_state(struct opp_table *src_table,
> >  	int dest_pstate = -EINVAL;
> >  	int i;
> >  
> > +	/* Both OPP tables must belong to genpds */
> > +	if (unlikely(!src_table->is_genpd || !dst_table->is_genpd)) {
> 
> I have a platform_device, with a required-opps and with an associated
> genpd which does not implement set_performance_state(), but its parent
> genpd does.
> 
> This results in me arriving here with src_table of NULL, and boom...
> 
> 
> Looking at the very next statement in this function, it seems arriving
> here without src_table was valid up until this change.

Fixed as:

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 48ddd72d2c71..3f46e499d615 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -2694,12 +2694,6 @@ int dev_pm_opp_xlate_performance_state(struct opp_table *src_table,
        int dest_pstate = -EINVAL;
        int i;

-       /* Both OPP tables must belong to genpds */
-       if (unlikely(!src_table->is_genpd || !dst_table->is_genpd)) {
-               pr_err("%s: Performance state is only valid for genpds.\n", __func__);
-               return -EINVAL;
-       }
-
        /*
         * Normally the src_table will have the "required_opps" property set to
         * point to one of the OPPs in the dst_table, but in some cases the
@@ -2710,6 +2704,12 @@ int dev_pm_opp_xlate_performance_state(struct opp_table *src_table,
        if (!src_table || !src_table->required_opp_count)
                return pstate;

+       /* Both OPP tables must belong to genpds */
+       if (unlikely(!src_table->is_genpd || !dst_table->is_genpd)) {
+               pr_err("%s: Performance state is only valid for genpds.\n", __func__);
+               return -EINVAL;
+       }
+
        /* required-opps not fully initialized yet */
        if (lazy_linking_pending(src_table))
                return -EBUSY;

Thanks.

-- 
viresh