Re: [PATCH v3 4/7] clk: qcom: gdsc: call runtime PM functions for the provider device

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On 09/07/2021 21:54, Bjorn Andersson wrote:
On Fri 09 Jul 12:31 CDT 2021, Dmitry Baryshkov wrote:

In order to properly handle runtime PM status of the provider device,
call pm_runtime_get/pm_runtime_put on the clock controller device.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
  drivers/clk/qcom/gdsc.c | 66 ++++++++++++++++++++++++++++++++++++++---
  drivers/clk/qcom/gdsc.h |  2 ++
  2 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
index ccd36617d067..6bec31fccb09 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>
@@ -50,6 +51,30 @@ enum gdsc_status {
  	GDSC_ON
  };
+static int gdsc_pm_runtime_get(struct gdsc *sc)
+{
+	int ret;
+
+	if (!sc->rpm_dev)
+		return 0;
+
+	ret = pm_runtime_get_sync(sc->rpm_dev);
+	if (ret < 0) {
+		pm_runtime_put_noidle(sc->rpm_dev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int gdsc_pm_runtime_put(struct gdsc *sc)
+{
+	if (!sc->rpm_dev)
+		return 0;
+
+	return pm_runtime_put_sync(sc->rpm_dev);
+}
+
  /* Returns 1 if GDSC status is status, 0 if not, and < 0 on error */
  static int gdsc_check_status(struct gdsc *sc, enum gdsc_status status)
  {
@@ -232,9 +257,8 @@ static void gdsc_retain_ff_on(struct gdsc *sc)
  	regmap_update_bits(sc->regmap, sc->gdscr, mask, mask);
  }
-static int gdsc_enable(struct generic_pm_domain *domain)
+static int _gdsc_enable(struct gdsc *sc)
  {
-	struct gdsc *sc = domain_to_gdsc(domain);
  	int ret;
if (sc->pwrsts == PWRSTS_ON)
@@ -290,11 +314,28 @@ static int gdsc_enable(struct generic_pm_domain *domain)
  	return 0;
  }
-static int gdsc_disable(struct generic_pm_domain *domain)
+static int gdsc_enable(struct generic_pm_domain *domain)
  {
  	struct gdsc *sc = domain_to_gdsc(domain);
  	int ret;
+ ret = gdsc_pm_runtime_get(sc);
+	if (ret)
+		return ret;
+
+	ret = _gdsc_enable(sc);
+	if (ret) {
+		gdsc_pm_runtime_put(sc);

I presume what you do here is to leave the pm_runtime state of dispcc
active if we succeeded in enabling the gdsc. But the gdsc is a subdomain
of the parent domain, so the framework should take case of its
dependency.

So the reason for gdsc_pm_runtime_get()/put() in this code path is so
that you can access the dispcc registers, i.e. I think you should
get()/put() regardless of the return value.

pm domain code will handle enabling MMCX, so this code is not required strictly speaking. Ulf suggested adding it back, so I followed the suggestion. Maybe I misunderstood his suggestion.

putting pm_runtime after gdsc_enable does not sound like a logical case. However it would simplify code a bit. Let me try...


+		return ret;
+	}
+
+	return 0;
+}
+
+static int _gdsc_disable(struct gdsc *sc)
+{
+	int ret;
+
  	if (sc->pwrsts == PWRSTS_ON)
  		return gdsc_assert_reset(sc);
@@ -329,6 +370,18 @@ static int gdsc_disable(struct generic_pm_domain *domain)
  	return 0;
  }
+static int gdsc_disable(struct generic_pm_domain *domain)
+{
+	struct gdsc *sc = domain_to_gdsc(domain);
+	int ret;
+

If the gdsc is found to be on at initialization, the next operation that
will happen is gdsc_disable() and as you didn't activate the pm_runtime
state in gdsc_init() you would in theory get here with registers
unaccessible.

In practice though, the active gdsc should through the being a subdomain
of the parent domain keep power on for you, so you won't notice this
issue.

Nice catch.


But as above, I think you should wrap _gdsc_disable() in a get()/put()
pair.

+	ret = _gdsc_disable(sc);
+	if (ret)
+		return ret;
+
+	return gdsc_pm_runtime_put(sc);
+}
+
  static int gdsc_init(struct gdsc *sc)
  {
  	u32 mask, val;
@@ -425,6 +478,8 @@ int gdsc_register(struct gdsc_desc *desc,
  	for (i = 0; i < num; i++) {
  		if (!scs[i])
  			continue;
+		if (pm_runtime_enabled(dev))
+			scs[i]->rpm_dev = dev;
  		scs[i]->regmap = regmap;
  		scs[i]->rcdev = rcdev;
  		ret = gdsc_init(scs[i]);
@@ -486,7 +541,10 @@ void gdsc_unregister(struct gdsc_desc *desc)
   */
  int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain)
  {
+	struct gdsc *sc = domain_to_gdsc(domain);
+
  	/* Do nothing but give genpd the impression that we were successful */
-	return 0;
+	/* Get the runtime PM device only */
+	return gdsc_pm_runtime_get(sc);

Per above, if you let the framework deal with the gdsc's dependencies on
the parent domain and you only get()/put() for the sake of dispcc then
you don't need you don't need to do this to keep the subsequent
gdsc_disable() in balance.

  }
  EXPORT_SYMBOL_GPL(gdsc_gx_do_nothing_enable);
diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
index 5bb396b344d1..a82982df0a55 100644
--- a/drivers/clk/qcom/gdsc.h
+++ b/drivers/clk/qcom/gdsc.h
@@ -25,6 +25,7 @@ struct reset_controller_dev;
   * @resets: ids of resets associated with this gdsc
   * @reset_count: number of @resets
   * @rcdev: reset controller
+ * @rpm_dev: runtime PM device
   */
  struct gdsc {
  	struct generic_pm_domain	pd;
@@ -58,6 +59,7 @@ struct gdsc {
const char *supply;
  	struct regulator		*rsupply;
+	struct device 			*rpm_dev;

This isn't just the "runtime pm device", it's the device this gdsc is
associated with. So "dev" sounds sufficient to me, but that requires
that you have a separate bool rpm_enabled to remember if
pm_runtime_enabled() was true during probe.

So unless we need "dev" for something else this might be sufficient.

Regards,
Bjorn

  };
struct gdsc_desc {
--
2.30.2



--
With best wishes
Dmitry



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