soc/tegra: Introduce core power domain driver

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 value which satisfies all devices within a power domain. Add
driver for the core power domain which manages the voltage state of the
domain. This allows us to support a system-wide DVFS on Tegra.

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>

drivers/soc/tegra/Kconfig

@@ -16,6 +16,7 @@ config ARCH_TEGRA_2x_SOC
 	select SOC_TEGRA_COMMON
 	select SOC_TEGRA_FLOWCTRL
 	select SOC_TEGRA_PMC
+	select SOC_TEGRA_CORE_POWER_DOMAIN
 	select SOC_TEGRA20_VOLTAGE_COUPLER
 	select TEGRA_TIMER
 	help
@@ -31,6 +32,7 @@ config ARCH_TEGRA_3x_SOC
 	select SOC_TEGRA_COMMON
 	select SOC_TEGRA_FLOWCTRL
 	select SOC_TEGRA_PMC
+	select SOC_TEGRA_CORE_POWER_DOMAIN
 	select SOC_TEGRA30_VOLTAGE_COUPLER
 	select TEGRA_TIMER
 	help
@@ -170,3 +172,7 @@ config SOC_TEGRA20_VOLTAGE_COUPLER
 config SOC_TEGRA30_VOLTAGE_COUPLER
 	bool "Voltage scaling support for Tegra30 SoCs"
 	depends on ARCH_TEGRA_3x_SOC || COMPILE_TEST
+
+config SOC_TEGRA_CORE_POWER_DOMAIN
+	bool
+	select PM_GENERIC_DOMAINS

drivers/soc/tegra/Makefile

@@ -7,3 +7,4 @@ obj-$(CONFIG_SOC_TEGRA_PMC) += pmc.o
 obj-$(CONFIG_SOC_TEGRA_POWERGATE_BPMP) += powergate-bpmp.o
 obj-$(CONFIG_SOC_TEGRA20_VOLTAGE_COUPLER) += regulators-tegra20.o
 obj-$(CONFIG_SOC_TEGRA30_VOLTAGE_COUPLER) += regulators-tegra30.o
+obj-$(CONFIG_SOC_TEGRA_CORE_POWER_DOMAIN) += core-power-domain.o

drivers/soc/tegra/core-power-domain.c

@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NVIDIA Tegra SoC Core Power Domain Driver
+ */
+
+#include <linux/mutex.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+
+#include <soc/tegra/common.h>
+
+static struct lock_class_key tegra_core_domain_lock_class;
+static bool tegra_core_domain_state_synced;
+static DEFINE_MUTEX(tegra_core_lock);
+
+bool tegra_soc_core_domain_state_synced(void)
+{
+	return tegra_core_domain_state_synced;
+}
+
+static int tegra_genpd_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(&tegra_core_lock);
+	err = dev_pm_opp_set_opp(&genpd->dev, opp);
+	mutex_unlock(&tegra_core_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_genpd_opp_to_performance_state(struct generic_pm_domain *genpd,
+				     struct dev_pm_opp *opp)
+{
+	return dev_pm_opp_get_level(opp);
+}
+
+static int tegra_core_domain_probe(struct platform_device *pdev)
+{
+	struct generic_pm_domain *genpd;
+	struct opp_table *opp_table;
+	const char *rname = "power";
+	int err;
+
+	genpd = devm_kzalloc(&pdev->dev, sizeof(*genpd), GFP_KERNEL);
+	if (!genpd)
+		return -ENOMEM;
+
+	genpd->name = pdev->dev.of_node->name;
+	genpd->set_performance_state = tegra_genpd_set_performance_state;
+	genpd->opp_to_performance_state = tegra_genpd_opp_to_performance_state;
+
+	opp_table = devm_pm_opp_set_regulators(&pdev->dev, &rname, 1);
+	if (IS_ERR(opp_table))
+		return dev_err_probe(&pdev->dev, PTR_ERR(opp_table),
+				     "failed to set OPP regulator\n");
+
+	err = pm_genpd_init(genpd, NULL, false);
+	if (err) {
+		dev_err(&pdev->dev, "failed to init genpd: %d\n", err);
+		return err;
+	}
+
+	/*
+	 * We have a "PMC -> Core" hierarchy of the power domains where
+	 * PMC needs to resume and change performance (voltage) of the
+	 * Core domain from the PMC GENPD on/off callbacks, hence we need
+	 * to annotate the lock in order to remove confusion from the
+	 * lockdep checker when a nested access happens.
+	 */
+	lockdep_set_class(&genpd->mlock, &tegra_core_domain_lock_class);
+
+	err = of_genpd_add_provider_simple(pdev->dev.of_node, genpd);
+	if (err) {
+		dev_err(&pdev->dev, "failed to add genpd: %d\n", err);
+		goto remove_genpd;
+	}
+
+	return 0;
+
+remove_genpd:
+	pm_genpd_remove(genpd);
+
+	return err;
+}
+
+static void tegra_core_domain_set_synced(struct device *dev, bool synced)
+{
+	int err;
+
+	tegra_core_domain_state_synced = synced;
+
+	mutex_lock(&tegra_core_lock);
+	err = dev_pm_opp_sync_regulators(dev);
+	mutex_unlock(&tegra_core_lock);
+
+	if (err)
+		dev_err(dev, "failed to sync regulators: %d\n", err);
+}
+
+static void tegra_core_domain_sync_state(struct device *dev)
+{
+	tegra_core_domain_set_synced(dev, true);
+}
+
+static void tegra_core_domain_shutdown(struct platform_device *pdev)
+{
+	/*
+	 * Ensure that core voltage is at a level suitable for boot-up
+	 * before system is rebooted, which may be important for some
+	 * devices if regulators aren't reset on reboot. This is usually
+	 * the case if PMC soft-reboot is used.
+	 */
+	tegra_core_domain_set_synced(&pdev->dev, false);
+}
+
+static const struct of_device_id tegra_core_domain_match[] = {
+	{ .compatible = "nvidia,tegra20-core-domain", },
+	{ .compatible = "nvidia,tegra30-core-domain", },
+	{ }
+};
+
+static struct platform_driver tegra_core_domain_driver = {
+	.driver = {
+		.name = "tegra-core-power",
+		.of_match_table = tegra_core_domain_match,
+		.suppress_bind_attrs = true,
+		.sync_state = tegra_core_domain_sync_state,
+	},
+	.probe = tegra_core_domain_probe,
+	.shutdown = tegra_core_domain_shutdown,
+};
+builtin_platform_driver(tegra_core_domain_driver);

include/soc/tegra/common.h

@@ -22,6 +22,7 @@ struct tegra_core_opp_params {
 
 #ifdef CONFIG_ARCH_TEGRA
 bool soc_is_tegra(void);
+bool tegra_soc_core_domain_state_synced(void);
 int devm_tegra_core_dev_init_opp_table(struct device *dev,
 				       struct tegra_core_opp_params *params);
 #else
@@ -30,6 +31,11 @@ static inline bool soc_is_tegra(void)
 	return false;
 }
 
+static inline bool tegra_soc_core_domain_state_synced(void)
+{
+	return false;
+}
+
 static inline int
 devm_tegra_core_dev_init_opp_table(struct device *dev,
 				   struct tegra_core_opp_params *params)