On Fri, 9 Jul 2021 at 13:46, Dmitry Baryshkov
[off-list ref] wrote:

On Fri, 9 Jul 2021 at 12:33, Ulf Hansson [off-list ref] wrote:

quoted

On Fri, 9 Jul 2021 at 06:32, Dmitry Baryshkov
[off-list ref] wrote:

quoted

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 <redacted>

[...]

quoted

diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
index 51ed640e527b..9401d01533c8 100644
--- a/drivers/clk/qcom/gdsc.c
+++ b/drivers/clk/qcom/gdsc.c

@@ -427,6 +427,7 @@ 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;

@@ -439,6 +440,8 @@ int gdsc_register(struct gdsc_desc *desc,
                        continue;
                if (scs[i]->parent)
                        pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd);
+               else if (!IS_ERR_OR_NULL(dev->pm_domain))

So dev_pm_domain_attach() (which calls genpd_dev_pm_attach() is being
called for gdsc platform device from the platform bus', to try to
attach the device to its corresponding PM domain.

Looking a bit closer to genpd_dev_pm_attach(), I realize that we
shouldn't really try to attach a device to its PM domain, when its OF
node (dev->of_node) contains a "#power-domain-cells" specifier. This
is because it indicates that the device belongs to a genpd provider
itself. In this case, a "power-domains" specifier tells that it has a
parent domain.

I will post a patch that fixes this asap.

I think there is nothing to fix here. The dispcc/videocc drivers
provide clocks in addition to the gdsc power domain. And provided
clocks would definitely benefit from having the dispcc device being
attached to the power domain which governs clock registers (MMCX in
our case). Thus I think it is perfectly valid to have:

rpmhpd device:
 - provides MMCX domain.

dispcc device:
 - is attached to the MMCX domain,

We don't need this, it's redundant and weird to me.

Also I am kind of worried that you will hit another new path in genpd,
causing locking issues etc, as it has not been designed to work like
this (a provider device and a child domain sharing the same "parent").

 - provides MDSS_GDSC

It's perfectly fine that dispcc acts as a genpd provider. In this
case, the corresponding PM domain should be assigned as a child for
the parent MMCX domain. That should make this work, I think.

 - provides clocks

That sounds reasonable as well.

quoted

quoted

+                       pm_genpd_add_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
        }

        return of_genpd_add_provider_onecell(dev->of_node, data);

@@ -457,6 +460,8 @@ void gdsc_unregister(struct gdsc_desc *desc)
                        continue;
                if (scs[i]->parent)
                        pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd);
+               else if (!IS_ERR_OR_NULL(dev->pm_domain))

Ditto.

quoted

+                       pm_genpd_remove_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
        }
        of_genpd_del_provider(dev->of_node);
 }
--
2.30.2

Kind regards
Uffe