Re: [PATCH RESEND v3 3/5] clk: qcom: gdsc: Add set and get hwmode callbacks to switch GDSC mode

[Jagadeesh Kona]

On 11/2/2023 2:58 AM, Dmitry Baryshkov wrote:
> On Wed, 1 Nov 2023 at 11:06, Abel Vesa <abel.vesa@xxxxxxxxxx> wrote:
> > From: Jagadeesh Kona <quic_jkona@xxxxxxxxxxx>
> >
> > Add support for set and get hwmode callbacks to switch the GDSC between
> > SW and HW modes. Currently, the GDSC is moved to HW control mode
> > using HW_CTRL flag and if this flag is present, GDSC is moved to HW
> > mode as part of GDSC enable itself. The intention is to keep the
> > HW_CTRL flag functionality as is, since many older chipsets still use
> > this flag.
> >
> > Introduce a new HW_CTRL_TRIGGER flag to switch the GDSC back and forth
> > between HW/SW modes dynamically at runtime. If HW_CTRL_TRIGGER flag is
> > present, register set_hwmode_dev callback to switch the GDSC mode which
> > can be invoked from consumer drivers using dev_pm_genpd_set_hwmode
> > function. Unlike HW_CTRL flag, HW_CTRL_TRIGGER won't move the GDSC to HW
> > control mode as part of GDSC enable itself, GDSC will be moved to HW
> > control mode only when consumer driver explicity calls
> > dev_pm_genpd_set_hwmode to switch to HW mode. Also add the
> > dev_pm_genpd_get_hwmode to allow the consumers to read the actual
> > HW/SW mode from hardware.
>
> Can we add two new flags:
> - HW_CTRL_TRIGGER
> - DEFAULT_HW_TRIGGER
>
> And then define HW_CTRL as HW_CTRL_TRIGGER | DEFAULT_HW_TRIGGER ?
>
> This way older platforms will keep existing behaviour, but can
> gradually migrate to the new callbacks?

Thanks Dmitry for your review,

The current usecases we have for GDSC's are either use the existing 
HW_CTRL flag to switch the GDSC to HW mode in gdsc_enable() and back to 
SW mode in gdsc_disable(). The second usecase is don't switch GDSC mode 
in gdsc_enable() & gdsc_disable() at all, and switch the GDSC mode only 
in new callbacks when consumers explicitly request it using 
dev_pm_genpd_set_hwmode(), this can be achieved using the new 
HW_CTRL_TRIGGER flag.

By defining HW_CTRL as HW_CTRL_TRIGGER | DEFAULT_HW_TRIGGER, it switches 
the GDSC mode both in enable & disable callbacks and in new callbacks as 
well. But we currently don't have any usecase that requires this behaviour.

Thanks,
Jagadeesh

> > Signed-off-by: Jagadeesh Kona <quic_jkona@xxxxxxxxxxx>
> > Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
> > ---
> >   drivers/clk/qcom/gdsc.c | 32 ++++++++++++++++++++++++++++++++
> >   drivers/clk/qcom/gdsc.h |  1 +
> >   2 files changed, 33 insertions(+)
> >
> > diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> > index 5358e28122ab..c763524cd5da 100644
> > --- a/drivers/clk/qcom/gdsc.c
> > +++ b/drivers/clk/qcom/gdsc.c
> > @@ -363,6 +363,34 @@ static int gdsc_disable(struct generic_pm_domain *domain)
> >          return 0;
> >   }
> >
> > +static int gdsc_set_hwmode(struct generic_pm_domain *domain, struct device *dev, bool mode)
> > +{
> > +       struct gdsc *sc = domain_to_gdsc(domain);
> > +
> > +       if (sc->rsupply && !regulator_is_enabled(sc->rsupply)) {
> > +               pr_err("Cannot set mode while parent is disabled\n");
> > +               return -EIO;
> > +       }
> > +
> > +       return gdsc_hwctrl(sc, mode);
> > +}
> > +
> > +static bool gdsc_get_hwmode(struct generic_pm_domain *domain, struct device *dev)
> > +{
> > +       struct gdsc *sc = domain_to_gdsc(domain);
> > +       u32 val;
> > +       int ret;
> > +
> > +       ret = regmap_read(sc->regmap, sc->gdscr, &val);
> > +       if (ret)
> > +               return ret;
> > +
> > +       if (val & HW_CONTROL_MASK)
> > +               return true;
> > +
> > +       return false;
> > +}
> > +
> >   static int gdsc_init(struct gdsc *sc)
> >   {
> >          u32 mask, val;
> > @@ -451,6 +479,10 @@ static int gdsc_init(struct gdsc *sc)
> >                  sc->pd.power_off = gdsc_disable;
> >          if (!sc->pd.power_on)
> >                  sc->pd.power_on = gdsc_enable;
> > +       if (sc->flags & HW_CTRL_TRIGGER) {
> > +               sc->pd.set_hwmode_dev = gdsc_set_hwmode;
> > +               sc->pd.get_hwmode_dev = gdsc_get_hwmode;
> > +       }
> >
> >          ret = pm_genpd_init(&sc->pd, NULL, !on);
> >          if (ret)
> > diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> > index 803512688336..1e2779b823d1 100644
> > --- a/drivers/clk/qcom/gdsc.h
> > +++ b/drivers/clk/qcom/gdsc.h
> > @@ -67,6 +67,7 @@ struct gdsc {
> >   #define ALWAYS_ON      BIT(6)
> >   #define RETAIN_FF_ENABLE       BIT(7)
> >   #define NO_RET_PERIPH  BIT(8)
> > +#define HW_CTRL_TRIGGER        BIT(9)
> >          struct reset_controller_dev     *rcdev;
> >          unsigned int                    *resets;
> >          unsigned int                    reset_count;
> >
> > --
> > 2.34.1