Re: [PATCH v7 02/37] soc/tegra: pmc: Implement attach_dev() of power domain drivers

[Dmitry Osipenko <digetx@gmail.com>]

09.08.2021 17:15, Ulf Hansson пишет:
>> We did that in a previous versions of this series where drivers were
>> calling devm_tegra_core_dev_init_opp_table() helper during the probe to
>> initialize performance state of the domain. Moving OPP state
>> initialization into central place made drivers cleaner by removing the
>> boilerplate code.
> I am not against doing this in a central place, like $subject patch
> suggests. As a matter of fact, it makes perfect sense to me.
> 
> However, what I am concerned about, is that you require to use genpd
> internal data structures to do it. I think we should try to avoid
> that.

Alright, what do you think about this:

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index a934c679e6ce..5faed62075e9 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -2669,12 +2669,37 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
 	dev->pm_domain->detach = genpd_dev_pm_detach;
 	dev->pm_domain->sync = genpd_dev_pm_sync;
 
+	if (pd->default_performance_state) {
+		unsigned int default_pstate;
+
+		ret = pd->default_performance_state(pd, dev);
+		if (ret < 0) {
+			dev_err(dev, "failed to get default performance state for PM domain %s: %d\n",
+				pd->name, ret);
+			goto out;
+		}
+
+		default_pstate = ret;
+
+		if (power_on) {
+			ret = dev_pm_genpd_set_performance_state(dev, default_pstate);
+			if (ret) {
+				dev_err(dev, "failed to set default performance state %u for PM domain %s: %d\n",
+					default_pstate, pd->name, ret);
+				goto out;
+			}
+		} else {
+			dev_gpd_data(dev)->rpm_pstate = default_pstate;
+		}
+	}
+
 	if (power_on) {
 		genpd_lock(pd);
 		ret = genpd_power_on(pd, 0);
 		genpd_unlock(pd);
 	}
 
+out:
 	if (ret)
 		genpd_remove_device(pd, dev);
 
diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
index 81d1f019fa0c..9efb55f52462 100644
--- a/drivers/soc/tegra/pmc.c
+++ b/drivers/soc/tegra/pmc.c
@@ -518,15 +518,14 @@ static const char * const tegra_emc_compats[] = {
  * We retrieve clock rate of the attached device and initialize domain's
  * performance state in accordance to the clock rate.
  */
-static int tegra_pmc_pd_attach_dev(struct generic_pm_domain *genpd,
-				   struct device *dev)
+static int tegra_pmc_genpd_default_perf_state(struct generic_pm_domain *genpd,
+					      struct device *dev)
 {
-	struct generic_pm_domain_data *gpd_data = dev_gpd_data(dev);
 	struct opp_table *opp_table, *pd_opp_table;
 	struct generic_pm_domain *core_genpd;
 	struct dev_pm_opp *opp, *pd_opp;
-	unsigned long rate, state;
 	struct gpd_link *link;
+	unsigned long rate;
 	struct clk *clk;
 	u32 hw_version;
 	int ret;
@@ -633,8 +632,7 @@ static int tegra_pmc_pd_attach_dev(struct generic_pm_domain *genpd,
 	 * RPM-resume of the device.  This means that drivers don't need to
 	 * explicitly initialize performance state.
 	 */
-	state = pm_genpd_opp_to_performance_state(&core_genpd->dev, pd_opp);
-	gpd_data->rpm_pstate = state;
+	ret = pm_genpd_opp_to_performance_state(&core_genpd->dev, pd_opp);
 	dev_pm_opp_put(pd_opp);
 
 put_pd_opp_table:
@@ -1383,7 +1381,7 @@ static int tegra_powergate_add(struct tegra_pmc *pmc, struct device_node *np)
 
 	pg->id = id;
 	pg->genpd.name = np->name;
-	pg->genpd.attach_dev = tegra_pmc_pd_attach_dev;
+	pg->genpd.default_performance_state = tegra_pmc_genpd_default_perf_state;
 	pg->genpd.power_off = tegra_genpd_power_off;
 	pg->genpd.power_on = tegra_genpd_power_on;
 	pg->pmc = pmc;
@@ -1500,7 +1498,7 @@ static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
 		return -ENOMEM;
 
 	genpd->name = np->name;
-	genpd->attach_dev = tegra_pmc_pd_attach_dev;
+	genpd->default_performance_state = tegra_pmc_genpd_default_perf_state;
 	genpd->set_performance_state = tegra_pmc_core_pd_set_performance_state;
 	genpd->opp_to_performance_state = tegra_pmc_core_pd_opp_to_performance_state;
 
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 21a0577305ef..cd4867817ca5 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -143,6 +143,8 @@ struct generic_pm_domain {
 			  struct device *dev);
 	void (*detach_dev)(struct generic_pm_domain *domain,
 			   struct device *dev);
+	int (*default_performance_state)(struct generic_pm_domain *domain,
+					 struct device *dev);
 	unsigned int flags;		/* Bit field of configs for genpd */
 	struct genpd_power_state *states;
 	void (*free_states)(struct genpd_power_state *states,

>> I can revert back to the previous variant, although this variant works
>> well too.
> I looked at that code and in that path we end up calling
> dev_pm_opp_set_rate(), after it has initialized the opp table for the
> device.
> 
> Rather than doing the OF parsing above to find out the current state
> for the device, why can't you just call dev_pm_opp_set_rate() to
> initialize a proper vote instead?
> 

For some devices clock rate is either preset by bootloader, or by clk driver, or by assigned-clocks in a device-tree. And then I don't see what's the difference in comparison to initialization for the current rate.

For some devices, like memory controller, we can't just change the clock rate because it's a complex procedure and some boards will use fixed rate, but the power vote still must be initialized.