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

[Bjorn Andersson]

On Mon 05 Jul 00:40 CDT 2021, Rajendra Nayak wrote:
> 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.

Thanks for confirming my understanding.

> 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?
> 

I can certainly add a Cc: stable@ as I'm applying this.

May I have your R-b?


PS. Do you have any input on patch 2/2? That actually solves a practical
problem we're seeing. Would it perhaps aid in your need for the new
"assigned-opp-level" property?

Regards,
Bjorn