[PATCH v1 02/13] soc/tegra: regulators: Bump voltages on system reboot

From: Dmitry Osipenko
Date: Thu May 20 2021 - 19:09:01 EST

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Ensure that SoC voltages are at a level suitable for a system reboot.
This is important for some devices that use CPU reset method for the
rebooting. SoC CPU and core voltages now are be restored to a level
that is suitable for rebooting. This patch fixes hang on reboot on
Asus Transformer TF101, it was also reported as fixing some of reboot
issues on Toshiba AC100.

Reported-by: Nikola Milosavljević <mnidza@xxxxxxxxxxx>
Tested-by: Nikola Milosavljević <mnidza@xxxxxxxxxxx> # TF101
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
drivers/soc/tegra/regulators-tegra20.c | 75 ++++++++++++++++++++++++-
drivers/soc/tegra/regulators-tegra30.c | 78 +++++++++++++++++++++++++-
2 files changed, 151 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/tegra/regulators-tegra20.c b/drivers/soc/tegra/regulators-tegra20.c
index 367a71a3cd10..3479be5ee494 100644
--- a/drivers/soc/tegra/regulators-tegra20.c
+++ b/drivers/soc/tegra/regulators-tegra20.c
@@ -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);
diff --git a/drivers/soc/tegra/regulators-tegra30.c b/drivers/soc/tegra/regulators-tegra30.c
index 0e776b20f625..6e4f3d9e7be1 100644
--- a/drivers/soc/tegra/regulators-tegra30.c
+++ b/drivers/soc/tegra/regulators-tegra30.c
@@ -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>
@@ -22,7 +23,10 @@ struct tegra_regulator_coupler {
struct regulator_coupler coupler;
struct regulator_dev *core_rdev;
struct regulator_dev *cpu_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 *
@@ -172,6 +176,10 @@ static int tegra30_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
@@ -195,6 +203,10 @@ static int tegra30_voltage_update(struct tegra_regulator_coupler *tegra,
if (err)
return err;

+ /* restore boot voltage level */
+ if (tegra->sys_reboot_mode)
+ cpu_min_uV = max(cpu_min_uV, tegra->cpu_min_uV);
+
if (core_min_limited_uV > core_uV) {
pr_err("core voltage constraint violated: %d %d %d\n",
core_uV, core_min_limited_uV, cpu_uV);
@@ -263,9 +275,56 @@ static int tegra30_regulator_balance_voltage(struct regulator_coupler *coupler,
return -EINVAL;
}

+ tegra->sys_reboot_mode = READ_ONCE(tegra->sys_reboot_mode_req);
+
return tegra30_voltage_update(tegra, cpu_rdev, core_rdev);
}

+static int tegra30_regulator_prepare_reboot(struct tegra_regulator_coupler *tegra,
+ bool sys_reboot_mode)
+{
+ int err;
+
+ if (!tegra->core_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 tegra30_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 = tegra30_regulator_prepare_reboot(tegra, true);
+
+ return notifier_from_errno(ret);
+}
+
static int tegra30_regulator_attach(struct regulator_coupler *coupler,
struct regulator_dev *rdev)
{
@@ -292,6 +351,17 @@ static int tegra30_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;
+
+ /* bring regulators to the state that is safe for reboot */
+ tegra30_regulator_prepare_reboot(tegra, false);
+
if (tegra->core_rdev == rdev) {
tegra->core_rdev = NULL;
return 0;
@@ -311,13 +381,19 @@ static struct tegra_regulator_coupler tegra30_coupler = {
.detach_regulator = tegra30_regulator_detach,
.balance_voltage = tegra30_regulator_balance_voltage,
},
+ .reboot_notifier.notifier_call = tegra30_regulator_reboot,
};

static int __init tegra_regulator_coupler_init(void)
{
+ int err;
+
if (!of_machine_is_compatible("nvidia,tegra30"))
return 0;

+ err = register_reboot_notifier(&tegra30_coupler.reboot_notifier);
+ WARN_ON(err);
+
return regulator_coupler_register(&tegra30_coupler.coupler);
}
arch_initcall(tegra_regulator_coupler_init);
--
2.30.2

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