NVIDIA Tegra memory and power management changes for 5.14

index e20e77e4c159..aae978c0c148 100644
@@ -4111,6 +4111,29 @@ int regulator_set_voltage_time_sel(struct regulator_dev *rdev,
 }
 EXPORT_SYMBOL_GPL(regulator_set_voltage_time_sel);
 
+int regulator_sync_voltage_rdev(struct regulator_dev *rdev)
+{
+	int ret;
+
+	regulator_lock(rdev);
+
+	if (!rdev->desc->ops->set_voltage &&
+	    !rdev->desc->ops->set_voltage_sel) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* balance only, if regulator is coupled */
+	if (rdev->coupling_desc.n_coupled > 1)
+		ret = regulator_balance_voltage(rdev, PM_SUSPEND_ON);
+	else
+		ret = -EOPNOTSUPP;
+
+out:
+	regulator_unlock(rdev);
+	return ret;
+}
+
 /**
  * regulator_sync_voltage - re-apply last regulator output voltage
  * @regulator: regulator source

index 4ea520c248e9..35e5a611db81 100644
@@ -540,6 +540,7 @@ int regulator_set_current_limit_regmap(struct regulator_dev *rdev,
 int regulator_get_current_limit_regmap(struct regulator_dev *rdev);
 void *regulator_get_init_drvdata(struct regulator_init_data *reg_init_data);
 int regulator_set_ramp_delay_regmap(struct regulator_dev *rdev, int ramp_delay);
+int regulator_sync_voltage_rdev(struct regulator_dev *rdev);
 
 /*
  * Helper functions intended to be used by regulator drivers prior registering

index 367a71a3cd10..3479be5ee494 100644
@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/of.h>
+#include <linux/reboot.h>
 #include <linux/regulator/coupler.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>

@@ -21,7 +22,10 @@ struct tegra_regulator_coupler {
 	struct regulator_dev *core_rdev;
 	struct regulator_dev *cpu_rdev;
 	struct regulator_dev *rtc_rdev;
-	int core_min_uV;
+	struct notifier_block reboot_notifier;
+	int core_min_uV, cpu_min_uV;
+	bool sys_reboot_mode_req;
+	bool sys_reboot_mode;
 };
 
 static inline struct tegra_regulator_coupler *

@@ -242,6 +246,10 @@ static int tegra20_cpu_voltage_update(struct tegra_regulator_coupler *tegra,
 	if (cpu_uV < 0)
 		return cpu_uV;
 
+	/* store boot voltage level */
+	if (!tegra->cpu_min_uV)
+		tegra->cpu_min_uV = cpu_uV;
+
 	/*
 	 * CPU's regulator may not have any consumers, hence the voltage
 	 * must not be changed in that case because CPU simply won't

@@ -250,6 +258,10 @@ static int tegra20_cpu_voltage_update(struct tegra_regulator_coupler *tegra,
 	if (!cpu_min_uV_consumers)
 		cpu_min_uV = cpu_uV;
 
+	/* restore boot voltage level */
+	if (tegra->sys_reboot_mode)
+		cpu_min_uV = max(cpu_min_uV, tegra->cpu_min_uV);
+
 	if (cpu_min_uV > cpu_uV) {
 		err = tegra20_core_rtc_update(tegra, core_rdev, rtc_rdev,
 					      cpu_uV, cpu_min_uV);

@@ -290,6 +302,8 @@ static int tegra20_regulator_balance_voltage(struct regulator_coupler *coupler,
 		return -EINVAL;
 	}
 
+	tegra->sys_reboot_mode = READ_ONCE(tegra->sys_reboot_mode_req);
+
 	if (rdev == cpu_rdev)
 		return tegra20_cpu_voltage_update(tegra, cpu_rdev,
 						  core_rdev, rtc_rdev);

@@ -303,6 +317,51 @@ static int tegra20_regulator_balance_voltage(struct regulator_coupler *coupler,
 	return -EPERM;
 }
 
+static int tegra20_regulator_prepare_reboot(struct tegra_regulator_coupler *tegra,
+					    bool sys_reboot_mode)
+{
+	int err;
+
+	if (!tegra->core_rdev || !tegra->rtc_rdev || !tegra->cpu_rdev)
+		return 0;
+
+	WRITE_ONCE(tegra->sys_reboot_mode_req, true);
+
+	/*
+	 * Some devices use CPU soft-reboot method and in this case we
+	 * should ensure that voltages are sane for the reboot by restoring
+	 * the minimum boot levels.
+	 */
+	err = regulator_sync_voltage_rdev(tegra->cpu_rdev);
+	if (err)
+		return err;
+
+	err = regulator_sync_voltage_rdev(tegra->core_rdev);
+	if (err)
+		return err;
+
+	WRITE_ONCE(tegra->sys_reboot_mode_req, sys_reboot_mode);
+
+	return 0;
+}
+
+static int tegra20_regulator_reboot(struct notifier_block *notifier,
+				    unsigned long event, void *cmd)
+{
+	struct tegra_regulator_coupler *tegra;
+	int ret;
+
+	if (event != SYS_RESTART)
+		return NOTIFY_DONE;
+
+	tegra = container_of(notifier, struct tegra_regulator_coupler,
+			     reboot_notifier);
+
+	ret = tegra20_regulator_prepare_reboot(tegra, true);
+
+	return notifier_from_errno(ret);
+}
+
 static int tegra20_regulator_attach(struct regulator_coupler *coupler,
 				    struct regulator_dev *rdev)
 {

@@ -335,6 +394,14 @@ static int tegra20_regulator_detach(struct regulator_coupler *coupler,
 {
 	struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
 
+	/*
+	 * We don't expect regulators to be decoupled during reboot,
+	 * this may race with the reboot handler and shouldn't ever
+	 * happen in practice.
+	 */
+	if (WARN_ON_ONCE(system_state > SYSTEM_RUNNING))
+		return -EPERM;
+
 	if (tegra->core_rdev == rdev) {
 		tegra->core_rdev = NULL;
 		return 0;

@@ -359,13 +426,19 @@ static struct tegra_regulator_coupler tegra20_coupler = {
 		.detach_regulator = tegra20_regulator_detach,
 		.balance_voltage = tegra20_regulator_balance_voltage,
 	},
+	.reboot_notifier.notifier_call = tegra20_regulator_reboot,
 };
 
 static int __init tegra_regulator_coupler_init(void)
 {
+	int err;
+
 	if (!of_machine_is_compatible("nvidia,tegra20"))
 		return 0;
 
+	err = register_reboot_notifier(&tegra20_coupler.reboot_notifier);
+	WARN_ON(err);
+
 	return regulator_coupler_register(&tegra20_coupler.coupler);
 }
 arch_initcall(tegra_regulator_coupler_init);

127 lines not on this page · raw message

index 98027a76ce3d..744280ecab5f 100644
@@ -6,6 +6,15 @@
 #ifndef __SOC_TEGRA_COMMON_H__
 #define __SOC_TEGRA_COMMON_H__
 
+#include <linux/types.h>
+
+#ifdef CONFIG_ARCH_TEGRA
 bool soc_is_tegra(void);
+#else
+static inline bool soc_is_tegra(void)
+{
+	return false;
+}
+#endif
 
 #endif /* __SOC_TEGRA_COMMON_H__ */

index 3dc54f59cafe..cd33e99249c3 100644
@@ -3,9 +3,16 @@
  * Copyright (C) 2014 NVIDIA CORPORATION.  All rights reserved.
  */
 
+#define dev_fmt(fmt)	"tegra-soc: " fmt
+
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/export.h>
 #include <linux/of.h>
+#include <linux/pm_opp.h>
 
 #include <soc/tegra/common.h>
+#include <soc/tegra/fuse.h>
 
 static const struct of_device_id tegra_machine_match[] = {
 	{ .compatible = "nvidia,tegra20", },

@@ -31,3 +38,93 @@ bool soc_is_tegra(void)
 
 	return match != NULL;
 }
+
+static int tegra_core_dev_init_opp_state(struct device *dev)
+{
+	unsigned long rate;
+	struct clk *clk;
+	int err;
+
+	clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(clk)) {
+		dev_err(dev, "failed to get clk: %pe\n", clk);
+		return PTR_ERR(clk);
+	}
+
+	rate = clk_get_rate(clk);
+	if (!rate) {
+		dev_err(dev, "failed to get clk rate\n");
+		return -EINVAL;
+	}
+
+	/* first dummy rate-setting initializes voltage vote */
+	err = dev_pm_opp_set_rate(dev, rate);
+	if (err) {
+		dev_err(dev, "failed to initialize OPP clock: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+/**
+ * devm_tegra_core_dev_init_opp_table() - initialize OPP table
+ * @dev: device for which OPP table is initialized
+ * @params: pointer to the OPP table configuration
+ *
+ * This function will initialize OPP table and sync OPP state of a Tegra SoC
+ * core device.
+ *
+ * Return: 0 on success or errorno.
+ */
+int devm_tegra_core_dev_init_opp_table(struct device *dev,
+				       struct tegra_core_opp_params *params)
+{
+	u32 hw_version;
+	int err;
+
+	err = devm_pm_opp_set_clkname(dev, NULL);
+	if (err) {
+		dev_err(dev, "failed to set OPP clk: %d\n", err);
+		return err;
+	}
+
+	/* Tegra114+ doesn't support OPP yet */
+	if (!of_machine_is_compatible("nvidia,tegra20") &&
+	    !of_machine_is_compatible("nvidia,tegra30"))
+		return -ENODEV;
+
+	if (of_machine_is_compatible("nvidia,tegra20"))
+		hw_version = BIT(tegra_sku_info.soc_process_id);
+	else
+		hw_version = BIT(tegra_sku_info.soc_speedo_id);
+
+	err = devm_pm_opp_set_supported_hw(dev, &hw_version, 1);
+	if (err) {
+		dev_err(dev, "failed to set OPP supported HW: %d\n", err);
+		return err;
+	}
+
+	/*
+	 * Older device-trees have an empty OPP table, we will get
+	 * -ENODEV from devm_pm_opp_of_add_table() in this case.
+	 */
+	err = devm_pm_opp_of_add_table(dev);
+	if (err) {
+		if (err == -ENODEV)
+			dev_err_once(dev, "OPP table not found, please update device-tree\n");
+		else
+			dev_err(dev, "failed to add OPP table: %d\n", err);
+
+		return err;
+	}
+
+	if (params->init_state) {
+		err = tegra_core_dev_init_opp_state(dev);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_tegra_core_dev_init_opp_table);

index 744280ecab5f..af41ad80ec21 100644
@@ -6,15 +6,37 @@
 #ifndef __SOC_TEGRA_COMMON_H__
 #define __SOC_TEGRA_COMMON_H__
 
+#include <linux/errno.h>
 #include <linux/types.h>
 
+struct device;
+
+/**
+ * Tegra SoC core device OPP table configuration
+ *
+ * @init_state: pre-initialize OPP state of a device
+ */
+struct tegra_core_opp_params {
+	bool init_state;
+};
+
 #ifdef CONFIG_ARCH_TEGRA
 bool soc_is_tegra(void);
+
+int devm_tegra_core_dev_init_opp_table(struct device *dev,
+				       struct tegra_core_opp_params *params);
 #else
 static inline bool soc_is_tegra(void)
 {
 	return false;
 }
+
+static inline int
+devm_tegra_core_dev_init_opp_table(struct device *dev,
+				   struct tegra_core_opp_params *params)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif /* __SOC_TEGRA_COMMON_H__ */

index 78cbc787a4dc..990701f788bc 100644
@@ -52,14 +52,28 @@ struct tegra_sku_info {
 	enum tegra_revision revision;
 };
 
+#ifdef CONFIG_ARCH_TEGRA
+extern struct tegra_sku_info tegra_sku_info;
 u32 tegra_read_straps(void);
 u32 tegra_read_ram_code(void);
 int tegra_fuse_readl(unsigned long offset, u32 *value);
-
-#ifdef CONFIG_ARCH_TEGRA
-extern struct tegra_sku_info tegra_sku_info;
 #else
 static struct tegra_sku_info tegra_sku_info __maybe_unused;
+
+static inline u32 tegra_read_straps(void)
+{
+	return 0;
+}
+
+static inline u32 tegra_read_ram_code(void)
+{
+	return 0;
+}
+
+static inline int tegra_fuse_readl(unsigned long offset, u32 *value)
+{
+	return -ENODEV;
+}
 #endif
 
 struct device *tegra_soc_device_register(void);

index 8e3b78bb2ac2..4a582eae82ef 100644
@@ -743,11 +743,6 @@ static int tegra_powergate_enable_clocks(struct tegra_powergate *pg)
 	return err;
 }
 
-int __weak tegra210_clk_handle_mbist_war(unsigned int id)
-{
-	return 0;
-}
-
 static int tegra_powergate_power_up(struct tegra_powergate *pg,
 				    bool disable_clocks)
 {

124 lines not on this page · raw message

index 5699d909abc2..a21ca8e0841a 100644
@@ -272,8 +272,8 @@
 #define EMC_PUTERM_ADJ				0x574
 
 #define DRAM_DEV_SEL_ALL			0
-#define DRAM_DEV_SEL_0				(2 << 30)
-#define DRAM_DEV_SEL_1				(1 << 30)
+#define DRAM_DEV_SEL_0				BIT(31)
+#define DRAM_DEV_SEL_1				BIT(30)
 
 #define EMC_CFG_POWER_FEATURES_MASK		\
 	(EMC_CFG_DYN_SREF | EMC_CFG_DRAM_ACPD | EMC_CFG_DRAM_CLKSTOP_SR | \

index 829f6d673c96..a2f2738ccb94 100644
@@ -150,8 +150,8 @@
 #define EMC_SELF_REF_CMD_ENABLED		BIT(0)
 
 #define DRAM_DEV_SEL_ALL			(0 << 30)
-#define DRAM_DEV_SEL_0				(2 << 30)
-#define DRAM_DEV_SEL_1				(1 << 30)
+#define DRAM_DEV_SEL_0				BIT(31)
+#define DRAM_DEV_SEL_1				BIT(30)
 #define DRAM_BROADCAST(num) \
 	((num) > 1 ? DRAM_DEV_SEL_ALL : DRAM_DEV_SEL_0)
 

index da8a0da8da79..a534197a5fb2 100644
@@ -908,49 +908,6 @@ static int tegra_emc_interconnect_init(struct tegra_emc *emc)
 	return err;
 }
 
-static int tegra_emc_opp_table_init(struct tegra_emc *emc)
-{
-	u32 hw_version = BIT(tegra_sku_info.soc_process_id);
-	struct opp_table *hw_opp_table;
-	int err;
-
-	hw_opp_table = dev_pm_opp_set_supported_hw(emc->dev, &hw_version, 1);
-	err = PTR_ERR_OR_ZERO(hw_opp_table);
-	if (err) {
-		dev_err(emc->dev, "failed to set OPP supported HW: %d\n", err);
-		return err;
-	}
-
-	err = dev_pm_opp_of_add_table(emc->dev);
-	if (err) {
-		if (err == -ENODEV)
-			dev_err(emc->dev, "OPP table not found, please update your device tree\n");
-		else
-			dev_err(emc->dev, "failed to add OPP table: %d\n", err);
-
-		goto put_hw_table;
-	}
-
-	dev_info_once(emc->dev, "OPP HW ver. 0x%x, current clock rate %lu MHz\n",
-		      hw_version, clk_get_rate(emc->clk) / 1000000);
-
-	/* first dummy rate-set initializes voltage state */
-	err = dev_pm_opp_set_rate(emc->dev, clk_get_rate(emc->clk));
-	if (err) {
-		dev_err(emc->dev, "failed to initialize OPP clock: %d\n", err);
-		goto remove_table;
-	}
-
-	return 0;
-
-remove_table:
-	dev_pm_opp_of_remove_table(emc->dev);
-put_hw_table:
-	dev_pm_opp_put_supported_hw(hw_opp_table);
-
-	return err;
-}
-
 static void devm_tegra_emc_unset_callback(void *data)
 {
 	tegra20_clk_set_emc_round_callback(NULL, NULL);

@@ -1077,6 +1034,7 @@ static int tegra_emc_devfreq_init(struct tegra_emc *emc)
 
 static int tegra_emc_probe(struct platform_device *pdev)
 {
+	struct tegra_core_opp_params opp_params = {};
 	struct device_node *np;
 	struct tegra_emc *emc;
 	int irq, err;

@@ -1122,7 +1080,9 @@ static int tegra_emc_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	err = tegra_emc_opp_table_init(emc);
+	opp_params.init_state = true;
+
+	err = devm_tegra_core_dev_init_opp_table(&pdev->dev, &opp_params);
 	if (err)
 		return err;
 

index a2f2738ccb94..63e1983f8a0d 100644
@@ -1480,49 +1480,6 @@ static int tegra_emc_interconnect_init(struct tegra_emc *emc)
 	return err;
 }
 
-static int tegra_emc_opp_table_init(struct tegra_emc *emc)
-{
-	u32 hw_version = BIT(tegra_sku_info.soc_speedo_id);
-	struct opp_table *hw_opp_table;
-	int err;
-
-	hw_opp_table = dev_pm_opp_set_supported_hw(emc->dev, &hw_version, 1);
-	err = PTR_ERR_OR_ZERO(hw_opp_table);
-	if (err) {
-		dev_err(emc->dev, "failed to set OPP supported HW: %d\n", err);
-		return err;
-	}
-
-	err = dev_pm_opp_of_add_table(emc->dev);
-	if (err) {
-		if (err == -ENODEV)
-			dev_err(emc->dev, "OPP table not found, please update your device tree\n");
-		else
-			dev_err(emc->dev, "failed to add OPP table: %d\n", err);
-
-		goto put_hw_table;
-	}
-
-	dev_info_once(emc->dev, "OPP HW ver. 0x%x, current clock rate %lu MHz\n",
-		      hw_version, clk_get_rate(emc->clk) / 1000000);
-
-	/* first dummy rate-set initializes voltage state */
-	err = dev_pm_opp_set_rate(emc->dev, clk_get_rate(emc->clk));
-	if (err) {
-		dev_err(emc->dev, "failed to initialize OPP clock: %d\n", err);
-		goto remove_table;
-	}
-
-	return 0;
-
-remove_table:
-	dev_pm_opp_of_remove_table(emc->dev);
-put_hw_table:
-	dev_pm_opp_put_supported_hw(hw_opp_table);
-
-	return err;
-}
-
 static void devm_tegra_emc_unset_callback(void *data)
 {
 	tegra20_clk_set_emc_round_callback(NULL, NULL);

@@ -1568,6 +1525,7 @@ static int tegra_emc_init_clk(struct tegra_emc *emc)
 
 static int tegra_emc_probe(struct platform_device *pdev)
 {
+	struct tegra_core_opp_params opp_params = {};
 	struct device_node *np;
 	struct tegra_emc *emc;
 	int err;

@@ -1617,7 +1575,9 @@ static int tegra_emc_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	err = tegra_emc_opp_table_init(emc);
+	opp_params.init_state = true;
+
+	err = devm_tegra_core_dev_init_opp_table(&pdev->dev, &opp_params);
 	if (err)
 		return err;
 

150 lines not on this page · raw message

index 7e07910b9b88..d8eee285fd58 100644
@@ -429,6 +429,8 @@ struct tegra_pmc {
 	struct irq_chip irq;
 
 	struct notifier_block clk_nb;
+
+	bool core_domain_state_synced;
 };
 
 static struct tegra_pmc *pmc = &(struct tegra_pmc) {

@@ -1298,6 +1300,11 @@ static int tegra_powergate_add(struct tegra_pmc *pmc, struct device_node *np)
 	return err;
 }
 
+bool tegra_pmc_core_domain_state_synced(void)
+{
+	return pmc->core_domain_state_synced;
+}
+
 static int
 tegra_pmc_core_pd_set_performance_state(struct generic_pm_domain *genpd,
 					unsigned int level)

@@ -3787,6 +3794,21 @@ static const struct of_device_id tegra_pmc_match[] = {
 	{ }
 };
 
+static void tegra_pmc_sync_state(struct device *dev)
+{
+	int err;
+
+	pmc->core_domain_state_synced = true;
+
+	/* this is a no-op if core regulator isn't used */
+	mutex_lock(&pmc->powergates_lock);
+	err = dev_pm_opp_sync_regulators(dev);
+	mutex_unlock(&pmc->powergates_lock);
+
+	if (err)
+		dev_err(dev, "failed to sync regulators: %d\n", err);
+}
+
 static struct platform_driver tegra_pmc_driver = {
 	.driver = {
 		.name = "tegra-pmc",

@@ -3795,6 +3817,7 @@ static struct platform_driver tegra_pmc_driver = {
 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_ARM)
 		.pm = &tegra_pmc_pm_ops,
 #endif
+		.sync_state = tegra_pmc_sync_state,
 	},
 	.probe = tegra_pmc_probe,
 };

index 361cb64246f7..d186bccd125d 100644
@@ -171,6 +171,8 @@ int tegra_io_rail_power_off(unsigned int id);
 void tegra_pmc_set_suspend_mode(enum tegra_suspend_mode mode);
 void tegra_pmc_enter_suspend_mode(enum tegra_suspend_mode mode);
 
+bool tegra_pmc_core_domain_state_synced(void);
+
 #else
 static inline int tegra_powergate_power_on(unsigned int id)
 {

@@ -227,6 +229,11 @@ static inline void tegra_pmc_enter_suspend_mode(enum tegra_suspend_mode mode)
 {
 }
 
+static inline bool tegra_pmc_core_domain_state_synced(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_SOC_TEGRA_PMC */
 
 #if defined(CONFIG_SOC_TEGRA_PMC) && defined(CONFIG_PM_SLEEP)

index 3479be5ee494..b8ce9fd0650d 100644
@@ -17,6 +17,8 @@
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
+#include <soc/tegra/pmc.h>
+
 struct tegra_regulator_coupler {
 	struct regulator_coupler coupler;
 	struct regulator_dev *core_rdev;

@@ -42,6 +44,21 @@ static int tegra20_core_limit(struct tegra_regulator_coupler *tegra,
 	int core_cur_uV;
 	int err;
 
+	/*
+	 * Tegra20 SoC has critical DVFS-capable devices that are
+	 * permanently-active or active at a boot time, like EMC
+	 * (DRAM controller) or Display controller for example.
+	 *
+	 * The voltage of a CORE SoC power domain shall not be dropped below
+	 * a minimum level, which is determined by device's clock rate.
+	 * This means that we can't fully allow CORE voltage scaling until
+	 * the state of all DVFS-critical CORE devices is synced.
+	 */
+	if (tegra_pmc_core_domain_state_synced() && !tegra->sys_reboot_mode) {
+		pr_info_once("voltage state synced\n");
+		return 0;
+	}
+
 	if (tegra->core_min_uV > 0)
 		return tegra->core_min_uV;
 

@@ -62,7 +79,7 @@ static int tegra20_core_limit(struct tegra_regulator_coupler *tegra,
 	 */
 	tegra->core_min_uV = core_max_uV;
 
-	pr_info("core minimum voltage limited to %duV\n", tegra->core_min_uV);
+	pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);
 
 	return tegra->core_min_uV;
 }

index 18fe53d0a870..e74bbc9c7859 100644
@@ -18,6 +18,7 @@
 #include <linux/regulator/machine.h>
 
 #include <soc/tegra/fuse.h>
+#include <soc/tegra/pmc.h>
 
 struct tegra_regulator_coupler {
 	struct regulator_coupler coupler;

@@ -43,6 +44,21 @@ static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
 	int core_cur_uV;
 	int err;
 
+	/*
+	 * Tegra30 SoC has critical DVFS-capable devices that are
+	 * permanently-active or active at a boot time, like EMC
+	 * (DRAM controller) or Display controller for example.
+	 *
+	 * The voltage of a CORE SoC power domain shall not be dropped below
+	 * a minimum level, which is determined by device's clock rate.
+	 * This means that we can't fully allow CORE voltage scaling until
+	 * the state of all DVFS-critical CORE devices is synced.
+	 */
+	if (tegra_pmc_core_domain_state_synced() && !tegra->sys_reboot_mode) {
+		pr_info_once("voltage state synced\n");
+		return 0;
+	}
+
 	if (tegra->core_min_uV > 0)
 		return tegra->core_min_uV;
 

@@ -63,7 +79,7 @@ static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
 	 */
 	tegra->core_min_uV = core_max_uV;
 
-	pr_info("core minimum voltage limited to %duV\n", tegra->core_min_uV);
+	pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);
 
 	return tegra->core_min_uV;
 }