Re: [PATCH 3/6] clk: qcom: gdsc: enable optional power domain support

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On Wed, 30 Jun 2021 at 20:11, Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Wed 30 Jun 10:47 CDT 2021, Dmitry Baryshkov wrote:
>
> > Hi,
> >
> > On Wed, 30 Jun 2021 at 18:00, Bjorn Andersson
> > <bjorn.andersson@linaro.org> wrote:
> > >
> > > On Wed 30 Jun 08:31 CDT 2021, Dmitry Baryshkov wrote:
> > >
> > > > On sm8250 dispcc and videocc registers are powered up by the MMCX power
> > > > domain. Currently we used a regulator to enable this domain on demand,
> > > > however this has some consequences, as genpd code is not reentrant.
> > > >
> > > > Teach Qualcomm clock controller code about setting up power domains and
> > > > using them for gdsc control.
> > > >
> > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > >
> > > There's a proposal to add a generic binding for statically assigning a
> > > performance states here:
> > >
> > > https://lore.kernel.org/linux-arm-msm/1622095949-2014-1-git-send-email-rnayak@codeaurora.org/

I checked this thread. It looks like Rajendra will also switch to the
"required-opps" property. So if that series goes in first, we can drop
the call to set_performance_state. If this one goes in first, we can
drop the set_performance_state call after getting Rajendra's work in.

> > >
> > >
> > > But that said, do you really need this?
> > >
> > > The requirement for driving MMCX to LOW_SVS on SM8250 (and NOM on
> > > SM8150/SC8180x) seems to only come from the fact that you push MDP_CLK
> > > to 460MHz in &mdss.
> > >
> > > But then in &mdss_mdp you do the same using an opp-table based on the
> > > actual MDP_CLK, which per its power-domains will scale MMCX accordingly.
> >
> > MDSS and DSI would bump up MMCX performance state requirements on
> > their own, depending on the frequency being selected.
> >
>
> Right, but as I copied things from the sm8250.dtsi to come up with
> sm8150/sc8180x.dtsi I concluded that as soon as the assigned-clockrate
> in &mdss kicks in I need the performance state to be at NOM.
>
> So keeping the assigned-clockrate in &mdss means that MMCX will never go
> below NOM.

No, because once MDP is fully running, it will lower the clock frequency:

# grep mdp_clk /sys/kernel/debug/clk/clk_summary
          disp_cc_mdss_mdp_clk_src       1        1        0
150000000          0     0  50000         ?
             disp_cc_mdss_mdp_clk       2        2        0
150000000          0     0  50000         Y

>
> > > So wouldn't it be sufficient to ensure that MDSS_GDSC is parented by
> > > MMCX and then use opp-tables associated with the devices that scales the
> > > clock and thereby actually carries the "required-opps".
> >
> > Actually no. I set the performance state in the qcom_cc_map, so that
> > further register access is possible. Initially I was doing this in the
> > qcom_cc_really_probe() and it was already too late.
> > Just to remind: this patchset is not about MDSS_GDSC being parented by
> > MMCX, it is about dispcc/videocc registers being gated with MMCX.
> >
>
> So you're saying that just enabling MMCX isn't enough to touch the
> dispcc/videocc registers? If that's the case it seems like MMCX's
> definition of "on" needs to be adjusted - because just specifying MMCX
> as the power-domain for dispcc/videocc and enabling pm_runtime should
> ensure that MMCX is enabled when the clock registers are accessed (I
> don't see anything like that for the GDSC part though).

No, it is not enough. If I comment out the set_performance_state call,
the board reboots.

However I can set the opps as low as RET and register access will work.
I'll run more experiments and if everything works as expected, I can
use retention or min_svs level in the next iteration.
Just note that downstream specifies low_svs as minimum voltage level
for MMCX regulator.

> I thought our problem you had was that you need to set a
> performance_state in order to clock up some of the clocks - e.g.
> MDP_CLK.

No, even register access needs proper perf state.

>
> > > I presume your testing indicates that it doesn't matter on sm8250, but
> > > as stated above, 460MHz on sm8150/sc8180x requires nominal, so per your
> > > suggestion we'd have to vote nominal in &mdss, which means that if the
> > > DPU decides to go to 200MHz the &mdss will still keep the voltage at
> > > NOM, even though the DPU's opp-table says that LOW_SVS is sufficient.
> >
> > Let me check whether LOW_SVS is really a requirement or if setting
> > MIN_SVS would also be sufficient for that. Interesting enough, from
> > the downstream drivers it looks like dispcc should be able to work
> > with MIN_SVS, while videocc would require LOW_SVS.
> >
>
> LOW_SVS is the documented requirement for ticking MDP_CLK at 460MHz on
> SM8250. But I would expect we don't need LOW_SVS in order to poke the
> registers in dispcc/videocc.
>
> Regards,
> Bjorn
>
> > >
> > > Regards,
> > > Bjorn
> > >
> > > > ---
> > > >  drivers/clk/qcom/common.c | 55 ++++++++++++++++++++++++++++++++++-----
> > > >  drivers/clk/qcom/gdsc.c   |  6 +++++
> > > >  2 files changed, 55 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c
> > > > index 60d2a78d1395..eeb5b8c93032 100644
> > > > --- a/drivers/clk/qcom/common.c
> > > > +++ b/drivers/clk/qcom/common.c
> > > > @@ -10,6 +10,8 @@
> > > >  #include <linux/clk-provider.h>
> > > >  #include <linux/reset-controller.h>
> > > >  #include <linux/of.h>
> > > > +#include <linux/pm_opp.h>
> > > > +#include <linux/pm_runtime.h>
> > > >
> > > >  #include "common.h"
> > > >  #include "clk-rcg.h"
> > > > @@ -76,6 +78,16 @@ qcom_cc_map(struct platform_device *pdev, const struct qcom_cc_desc *desc)
> > > >       struct resource *res;
> > > >       struct device *dev = &pdev->dev;
> > > >
> > > > +     if (of_find_property(dev->of_node, "required-opps", NULL)) {
> > > > +             int pd_opp;
> > > > +
> > > > +             pd_opp = of_get_required_opp_performance_state(dev->of_node, 0);
> > > > +             if (pd_opp < 0)
> > > > +                     return ERR_PTR(pd_opp);
> > > > +
> > > > +             dev_pm_genpd_set_performance_state(dev, pd_opp);
> > > > +     }
> > > > +
> > > >       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > >       base = devm_ioremap_resource(dev, res);
> > > >       if (IS_ERR(base))
> > > > @@ -224,6 +236,11 @@ static struct clk_hw *qcom_cc_clk_hw_get(struct of_phandle_args *clkspec,
> > > >       return cc->rclks[idx] ? &cc->rclks[idx]->hw : NULL;
> > > >  }
> > > >
> > > > +static void qcom_cc_pm_runtime_disable(void *data)
> > > > +{
> > > > +     pm_runtime_disable(data);
> > > > +}
> > > > +
> > > >  int qcom_cc_really_probe(struct platform_device *pdev,
> > > >                        const struct qcom_cc_desc *desc, struct regmap *regmap)
> > > >  {
> > > > @@ -236,11 +253,28 @@ int qcom_cc_really_probe(struct platform_device *pdev,
> > > >       struct clk_regmap **rclks = desc->clks;
> > > >       size_t num_clk_hws = desc->num_clk_hws;
> > > >       struct clk_hw **clk_hws = desc->clk_hws;
> > > > +     bool use_pm = false;
> > > >
> > > >       cc = devm_kzalloc(dev, sizeof(*cc), GFP_KERNEL);
> > > >       if (!cc)
> > > >               return -ENOMEM;
> > > >
> > > > +     if (of_find_property(dev->of_node, "required-opps", NULL)) {
> > > > +             use_pm = true;
> > > > +
> > > > +             pm_runtime_enable(dev);
> > > > +             ret = pm_runtime_get_sync(dev);
> > > > +             if (ret < 0) {
> > > > +                     pm_runtime_put(dev);
> > > > +                     pm_runtime_disable(dev);
> > > > +                     return ret;
> > > > +             }
> > > > +
> > > > +             ret = devm_add_action_or_reset(dev, qcom_cc_pm_runtime_disable, dev);
> > > > +             if (ret)
> > > > +                     return ret;
> > > > +     }
> > > > +
> > > >       reset = &cc->reset;
> > > >       reset->rcdev.of_node = dev->of_node;
> > > >       reset->rcdev.ops = &qcom_reset_ops;
> > > > @@ -251,7 +285,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
> > > >
> > > >       ret = devm_reset_controller_register(dev, &reset->rcdev);
> > > >       if (ret)
> > > > -             return ret;
> > > > +             goto err;
> > > >
> > > >       if (desc->gdscs && desc->num_gdscs) {
> > > >               scd = devm_kzalloc(dev, sizeof(*scd), GFP_KERNEL);
> > > > @@ -262,11 +296,11 @@ int qcom_cc_really_probe(struct platform_device *pdev,
> > > >               scd->num = desc->num_gdscs;
> > > >               ret = gdsc_register(scd, &reset->rcdev, regmap);
> > > >               if (ret)
> > > > -                     return ret;
> > > > +                     goto err;
> > > >               ret = devm_add_action_or_reset(dev, qcom_cc_gdsc_unregister,
> > > >                                              scd);
> > > >               if (ret)
> > > > -                     return ret;
> > > > +                     goto err;
> > > >       }
> > > >
> > > >       cc->rclks = rclks;
> > > > @@ -277,7 +311,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
> > > >       for (i = 0; i < num_clk_hws; i++) {
> > > >               ret = devm_clk_hw_register(dev, clk_hws[i]);
> > > >               if (ret)
> > > > -                     return ret;
> > > > +                     goto err;
> > > >       }
> > > >
> > > >       for (i = 0; i < num_clks; i++) {
> > > > @@ -286,14 +320,23 @@ int qcom_cc_really_probe(struct platform_device *pdev,
> > > >
> > > >               ret = devm_clk_register_regmap(dev, rclks[i]);
> > > >               if (ret)
> > > > -                     return ret;
> > > > +                     goto err;
> > > >       }
> > > >
> > > >       ret = devm_of_clk_add_hw_provider(dev, qcom_cc_clk_hw_get, cc);
> > > >       if (ret)
> > > > -             return ret;
> > > > +             goto err;
> > > > +
> > > > +     if (use_pm)
> > > > +             pm_runtime_put(dev);
> > > >
> > > >       return 0;
> > > > +
> > > > +err:
> > > > +     if (use_pm)
> > > > +             pm_runtime_put(dev);
> > > > +
> > > > +     return ret;
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(qcom_cc_really_probe);
> > > >
> > > > diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> > > > index 51ed640e527b..40c384bda4fc 100644
> > > > --- a/drivers/clk/qcom/gdsc.c
> > > > +++ b/drivers/clk/qcom/gdsc.c
> > > > @@ -11,6 +11,7 @@
> > > >  #include <linux/kernel.h>
> > > >  #include <linux/ktime.h>
> > > >  #include <linux/pm_domain.h>
> > > > +#include <linux/pm_runtime.h>
> > > >  #include <linux/regmap.h>
> > > >  #include <linux/regulator/consumer.h>
> > > >  #include <linux/reset-controller.h>
> > > > @@ -237,6 +238,8 @@ static int gdsc_enable(struct generic_pm_domain *domain)
> > > >       struct gdsc *sc = domain_to_gdsc(domain);
> > > >       int ret;
> > > >
> > > > +     pm_runtime_get_sync(domain->dev.parent);
> > > > +
> > > >       if (sc->pwrsts == PWRSTS_ON)
> > > >               return gdsc_deassert_reset(sc);
> > > >
> > > > @@ -326,6 +329,8 @@ static int gdsc_disable(struct generic_pm_domain *domain)
> > > >       if (sc->flags & CLAMP_IO)
> > > >               gdsc_assert_clamp_io(sc);
> > > >
> > > > +     pm_runtime_put(domain->dev.parent);
> > > > +
> > > >       return 0;
> > > >  }
> > > >
> > > > @@ -427,6 +432,7 @@ int gdsc_register(struct gdsc_desc *desc,
> > > >                       continue;
> > > >               scs[i]->regmap = regmap;
> > > >               scs[i]->rcdev = rcdev;
> > > > +             scs[i]->pd.dev.parent = desc->dev;
> > > >               ret = gdsc_init(scs[i]);
> > > >               if (ret)
> > > >                       return ret;
> > > > --
> > > > 2.30.2
> > > >
> >
> >
> >
> > --
> > With best wishes
> > Dmitry



-- 
With best wishes
Dmitry