Re: [PATCH 1/2] soc: qcom: rpmhpd: Use corner in power_off

[Rajendra Nayak]

On 7/5/2021 10:36 AM, Bjorn Andersson wrote:
> On Sun, Jul 4, 2021 at 11:27 PM Rajendra Nayak <rnayak@xxxxxxxxxxxxxx> wrote:
> > On 7/3/2021 6:24 AM, Bjorn Andersson wrote:
> > > rpmhpd_aggregate_corner() takes a corner as parameter, but in
> > > rpmhpd_power_off() the code requests the level of the first corner
> > > instead.
> > >
> > > In all (known) current cases the first corner has level 0, so this
> > > change should be a nop, but in case that there's a power domain with a
> > > non-zero lowest level this makes sure that rpmhpd_power_off() actually
> > > requests the lowest level - which is the closest to "power off" we can
> > > get.
> > >
> > > While touching the code, also skip the unnecessary zero-initialization
> > > of "ret".
> > >
> > > Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> > > ---
> > >    drivers/soc/qcom/rpmhpd.c | 5 ++---
> > >    1 file changed, 2 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/soc/qcom/rpmhpd.c b/drivers/soc/qcom/rpmhpd.c
> > > index 2daa17ba54a3..fa209b479ab3 100644
> > > --- a/drivers/soc/qcom/rpmhpd.c
> > > +++ b/drivers/soc/qcom/rpmhpd.c
> > > @@ -403,12 +403,11 @@ static int rpmhpd_power_on(struct generic_pm_domain *domain)
> > >    static int rpmhpd_power_off(struct generic_pm_domain *domain)
> > >    {
> > >        struct rpmhpd *pd = domain_to_rpmhpd(domain);
> > > -     int ret = 0;
> > > +     int ret;
> > >
> > >        mutex_lock(&rpmhpd_lock);
> > >
> > > -     ret = rpmhpd_aggregate_corner(pd, pd->level[0]);
> > > -
> > > +     ret = rpmhpd_aggregate_corner(pd, 0);
> >
> > This won't work for cases where pd->level[0] != 0, rpmh would just ignore this and keep the
> > resource at whatever corner it was previously at.
> > (unless command DB tells you a 0 is 'valid' for a resource, sending a 0 is a nop)
> > The right thing to do is to send in whatever command DB tells you is the lowest level that's valid,
> > which is pd->level[0].
>
> I'm afraid this doesn't make sense to me.
>
> In rpmh_power_on() if cmd-db tells us that we have [0, 64, ...] and we
> request 64 we rpmhpd_aggregate_corner(pd, 1); but in power off, if
> cmd-db would provide [64, ...] we would end up sending
> rpmhpd_aggregate_corner(pd, 64);
> So in power_on we request the corner (i.e. index in the array provided
> in cmd-db) and in power-off the same function takes the level?

ah that's right, I did not read the commit log properly and got confused.
Looks like this bug existed from the day this driver for merged :/, thanks
for catching it.
Does it make sense to also mark this fix for stable?

> Can you please help me understand what the actual number we're
> supposed to send to the RPMh is? Is it numbers in the range [0-15] or
> is it numbers such as {0, 64, 128, ...}?
>
> Afaict it's the prior (i.e. [0-15]), as this is what we currently do
> in both power_on and set_performance_state, and it happens to be what
> we send in power_off as long as the first level from cmd-db is 0.
>
> Regards,
> Bjorn
>
> > >        if (!ret)
> > >                pd->enabled = false;
> >
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> > of Code Aurora Forum, hosted by The Linux Foundation

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation