linux-kernel - Re: [PATCH] clk: qcom: gdsc: Ensure regulator init state matches GDSC state

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Date:   Tue, 29 Jun 2021 16:13:56 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Vinod Koul <vkoul@...nel.org>, dmitry.baryshkov@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] clk: qcom: gdsc: Ensure regulator init state matches
 GDSC state

On Tue 29 Jun 01:34 CDT 2021, Stephen Boyd wrote:

> Quoting Bjorn Andersson (2021-06-25 15:54:14)
> > As GDSCs are registered and found to be already enabled
> > gdsc_toggle_logic() will be invoked for votable GDSCs and ensure that
> > the vote is matching the hardware state. Part of this the related
> > regulator will be enabled.
> > 
> > But for non-votable GDSCs the regulator and GDSC status will be out of
> > sync and as the GDSC is later disabled regulator_disable() will face an
> > unbalanced enable-count, or something might turn off the supply under
> > the feet of the GDSC.
> > 
> > So ensure that the regulator is enabled even for non-votable GDSCs.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: 37416e554961 ("clk: qcom: gdsc: Handle GDSC regulator supplies")
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > ---
> >  drivers/clk/qcom/gdsc.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> > index 51ed640e527b..f7e7759cdb90 100644
> > --- a/drivers/clk/qcom/gdsc.c
> > +++ b/drivers/clk/qcom/gdsc.c
> > @@ -359,10 +359,17 @@ static int gdsc_init(struct gdsc *sc)
> >  
> >         /*
> >          * Votable GDSCs can be ON due to Vote from other masters.
> > -        * If a Votable GDSC is ON, make sure we have a Vote.
> > +        * If a Votable GDSC is ON, make sure we have a Vote. If
> > +        * non-votable, ensure that the supply is kept enabled (as
> > +        * is done by gdsc_enable).
> >          */
> > -       if ((sc->flags & VOTABLE) && on)
> > +       if ((sc->flags & VOTABLE) && on) {
> >                 gdsc_enable(&sc->pd);
> > +       } else if (on) {
> > +               ret = regulator_enable(sc->rsupply);
> > +               if (ret < 0)
> > +                       return ret;
> 
> Looking at this makes me think we've messed something up with
> gdsc_enable() being called or cherry-picking the regulator enable (and
> other stuff in this gdsc_init()) out of the enable path. Maybe we should
> have a followup patch that replaces the gdsc_enable() with
> gdsc_toggle_logic(sc, GDSC_ON) so that we know it isn't doing anything
> else during init like asserting a reset when presumably all we want to
> do is toggle the enable bit to assert our vote.
> 
> And I notice that we already call gdsc_toggle_logic() in gdsc_init(), so
> then we'll have a double regulator_enable() in the case of PWRSTS_ON?
> And then if the flag is ALWAYS_ON we'll call regulator_enable() yet
> again, but luckily only if it isn't on initially, phew! This code is
> quite twisted.
> 
> It would be super nice to make it more like
> 
> 	if (on) {
> 		/* It was on in hardware, sync kernel state */
> 		regulator_enable();
> 
> 		if (votable)
> 			write bit, why do any wait?
> 
> 		if (retain ff)
> 			write bit
> 	} else if (always_on) {
> 		/* Force on */
> 		gdsc_enable();
> 		on = true;
> 	}
> 
> 	if (on || ...)
> 

This does look cleaner, I will dig through the logic here once more
before figuring out what to do for v2.

Thanks,
Bjorn

> > +       }
> >  
> >         /*
> >          * Make sure the retain bit is set if the GDSC is already on, otherwise