soc/tegra: pmc: Add core power domain

NVIDIA Tegra SoCs have multiple power domains, each domain corresponds
to an external SoC power rail. Core power domain covers vast majority of
hardware blocks within a Tegra SoC. The voltage of a power domain should
be set to a level which satisfies all devices within the power domain.
Add support for the core power domain which controls voltage state of the
domain. This allows us to support system-wide DVFS on Tegra20-210 SoCs.
The PMC powergate domains now are sub-domains of the core domain, this
requires device-tree updating, older DTBs are unaffected and will continue
to work as before.

Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30
Tested-by: Paul Fertser <fercerpav@gmail.com> # PAZ00 T20
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20 and TK1 T124
Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
[treding@nvidia.com: squash lockdep class removal patch]
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/soc/tegra/Kconfig

@@ -144,6 +144,8 @@ config SOC_TEGRA_FLOWCTRL
 config SOC_TEGRA_PMC
 	bool
 	select GENERIC_PINCONF
+	select PM_OPP
+	select PM_GENERIC_DOMAINS
 
 config SOC_TEGRA_POWERGATE_BPMP
 	def_bool y

drivers/soc/tegra/pmc.c

@@ -38,6 +38,7 @@
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/platform_device.h>
 #include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
 #include <linux/reboot.h>
 #include <linux/regmap.h>
 #include <linux/reset.h>
@@ -1302,12 +1303,100 @@ static int tegra_powergate_add(struct tegra_pmc *pmc, struct device_node *np)
 	return err;
 }
 
+static int
+tegra_pmc_core_pd_set_performance_state(struct generic_pm_domain *genpd,
+					unsigned int level)
+{
+	struct dev_pm_opp *opp;
+	int err;
+
+	opp = dev_pm_opp_find_level_ceil(&genpd->dev, &level);
+	if (IS_ERR(opp)) {
+		dev_err(&genpd->dev, "failed to find OPP for level %u: %pe\n",
+			level, opp);
+		return PTR_ERR(opp);
+	}
+
+	mutex_lock(&pmc->powergates_lock);
+	err = dev_pm_opp_set_opp(pmc->dev, opp);
+	mutex_unlock(&pmc->powergates_lock);
+
+	dev_pm_opp_put(opp);
+
+	if (err) {
+		dev_err(&genpd->dev, "failed to set voltage to %duV: %d\n",
+			level, err);
+		return err;
+	}
+
+	return 0;
+}
+
+static unsigned int
+tegra_pmc_core_pd_opp_to_performance_state(struct generic_pm_domain *genpd,
+					   struct dev_pm_opp *opp)
+{
+	return dev_pm_opp_get_level(opp);
+}
+
+static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
+{
+	struct generic_pm_domain *genpd;
+	const char *rname = "core";
+	int err;
+
+	genpd = devm_kzalloc(pmc->dev, sizeof(*genpd), GFP_KERNEL);
+	if (!genpd)
+		return -ENOMEM;
+
+	genpd->name = np->name;
+	genpd->set_performance_state = tegra_pmc_core_pd_set_performance_state;
+	genpd->opp_to_performance_state = tegra_pmc_core_pd_opp_to_performance_state;
+
+	err = devm_pm_opp_set_regulators(pmc->dev, &rname, 1);
+	if (err)
+		return dev_err_probe(pmc->dev, err,
+				     "failed to set core OPP regulator\n");
+
+	err = pm_genpd_init(genpd, NULL, false);
+	if (err) {
+		dev_err(pmc->dev, "failed to init core genpd: %d\n", err);
+		return err;
+	}
+
+	err = of_genpd_add_provider_simple(np, genpd);
+	if (err) {
+		dev_err(pmc->dev, "failed to add core genpd: %d\n", err);
+		goto remove_genpd;
+	}
+
+	return 0;
+
+remove_genpd:
+	pm_genpd_remove(genpd);
+
+	return err;
+}
+
 static int tegra_powergate_init(struct tegra_pmc *pmc,
 				struct device_node *parent)
 {
+	struct of_phandle_args child_args, parent_args;
 	struct device_node *np, *child;
 	int err = 0;
 
+	/*
+	 * Core power domain is the parent of powergate domains, hence it
+	 * should be registered first.
+	 */
+	np = of_get_child_by_name(parent, "core-domain");
+	if (np) {
+		err = tegra_pmc_core_pd_add(pmc, np);
+		of_node_put(np);
+		if (err)
+			return err;
+	}
+
 	np = of_get_child_by_name(parent, "powergates");
 	if (!np)
 		return 0;
@@ -1318,6 +1407,21 @@ static int tegra_powergate_init(struct tegra_pmc *pmc,
 			of_node_put(child);
 			break;
 		}
+
+		if (of_parse_phandle_with_args(child, "power-domains",
+					       "#power-domain-cells",
+					       0, &parent_args))
+			continue;
+
+		child_args.np = child;
+		child_args.args_count = 0;
+
+		err = of_genpd_add_subdomain(&parent_args, &child_args);
+		of_node_put(parent_args.np);
+		if (err) {
+			of_node_put(child);
+			break;
+		}
 	}
 
 	of_node_put(np);
@@ -1361,6 +1465,12 @@ static void tegra_powergate_remove_all(struct device_node *parent)
 	}
 
 	of_node_put(np);
+
+	np = of_get_child_by_name(parent, "core-domain");
+	if (np) {
+		of_genpd_del_provider(np);
+		of_genpd_remove_last(np);
+	}
 }
 
 static const struct tegra_io_pad_soc *