[PATCH v2 3/3] soc/tegra: regulators: Add regulators coupler for Tegra30

Dmitry Osipenko
2019-07-25T15:21:06Z

Add regulators coupler for Tegra30 SoCs that performs voltage balancing
of a coupled regulators and thus provides voltage scaling functionality.

There are 2 coupled regulators on all Tegra30 SoCs: CORE and CPU. The
coupled regulator voltages shall be in a range of 300mV from each other
and CORE voltage shall be higher than the CPU by N mV, where N depends
on the CPU voltage.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/soc/tegra/Kconfig | 4 +
drivers/soc/tegra/Makefile | 1 +
drivers/soc/tegra/regulators-tegra30.c | 316 +++++++++++++++++++++++++
3 files changed, 321 insertions(+)
create mode 100644 drivers/soc/tegra/regulators-tegra30.c

diff --git a/drivers/soc/tegra/Kconfig b/drivers/soc/tegra/Kconfig
index 7986ab80e07a..bc86dc2f4198 100644
--- a/drivers/soc/tegra/Kconfig
+++ b/drivers/soc/tegra/Kconfig
@@ -28,6 +28,7 @@ config ARCH_TEGRA_3x_SOC
select PL310_ERRATA_769419 if CACHE_L2X0
select SOC_TEGRA_FLOWCTRL
select SOC_TEGRA_PMC
+ select SOC_TEGRA30_VOLTAGE_COUPLER
select TEGRA_TIMER
help
Support for NVIDIA Tegra T30 processor family, based on the
@@ -140,3 +141,6 @@ config SOC_TEGRA20_VOLTAGE_COUPLER
bool "Voltage scaling support for Tegra20 SoCs"
depends on ARCH_TEGRA_2x_SOC || COMPILE_TEST

+config SOC_TEGRA30_VOLTAGE_COUPLER
+ bool "Voltage scaling support for Tegra30 SoCs"
+ depends on ARCH_TEGRA_3x_SOC || COMPILE_TEST
diff --git a/drivers/soc/tegra/Makefile b/drivers/soc/tegra/Makefile
index 9f0bdd53bef8..9c809c1814bd 100644
--- a/drivers/soc/tegra/Makefile
+++ b/drivers/soc/tegra/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_SOC_TEGRA_FLOWCTRL) += flowctrl.o
obj-$(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
diff --git a/drivers/soc/tegra/regulators-tegra30.c b/drivers/soc/tegra/regulators-tegra30.c
new file mode 100644
index 000000000000..f19fccfe1a92
--- /dev/null
+++ b/drivers/soc/tegra/regulators-tegra30.c
@@ -0,0 +1,316 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Voltage regulators coupler for NVIDIA Tegra30
+// Copyright (C) 2019 GRATE-DRIVER project
+//
+// Voltage constraints borrowed from downstream kernel sources
+// Copyright (C) 2010-2011 NVIDIA Corporation
+
+#define pr_fmt(fmt) "tegra voltage-coupler: " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/regulator/coupler.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+
+#include <soc/tegra/fuse.h>
+
+struct tegra_regulator_coupler {
+ struct regulator_coupler coupler;
+ struct regulator_dev *core_rdev;
+ struct regulator_dev *cpu_rdev;
+ int core_min_uV;
+};
+
+static inline struct tegra_regulator_coupler *
+to_tegra_coupler(struct regulator_coupler *coupler)
+{
+ return container_of(coupler, struct tegra_regulator_coupler, coupler);
+}
+
+static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
+ struct regulator_dev *core_rdev)
+{
+ int core_min_uV = 0;
+ int core_max_uV;
+ int core_cur_uV;
+ int err;
+
+ if (tegra->core_min_uV > 0)
+ return tegra->core_min_uV;
+
+ core_cur_uV = regulator_get_voltage_rdev(core_rdev);
+ if (core_cur_uV < 0)
+ return core_cur_uV;
+
+ core_max_uV = max(core_cur_uV, 1200000);
+
+ err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
+ if (err)
+ return err;
+
+ /*
+ * Limit minimum CORE voltage to a value left from bootloader or,
+ * if it's unreasonably low value, to the most common 1.2v or to
+ * whatever maximum value defined via board's device-tree.
+ */
+ tegra->core_min_uV = core_max_uV;
+
+ pr_info("core minimum voltage limited to %duV\n", tegra->core_min_uV);
+
+ return tegra->core_min_uV;
+}
+
+static int tegra30_core_cpu_limit(int cpu_uV)
+{
+ if (cpu_uV < 800000)
+ return 950000;
+
+ if (cpu_uV < 900000)
+ return 1000000;
+
+ if (cpu_uV < 1000000)
+ return 1100000;
+
+ if (cpu_uV < 1100000)
+ return 1200000;
+
+ if (cpu_uV < 1250000) {
+ switch (tegra_sku_info.cpu_speedo_id) {
+ case 0 ... 1:
+ case 4:
+ case 7 ... 8:
+ return 1200000;
+
+ default:
+ return 1300000;
+ }
+ }
+
+ return -EINVAL;
+}
+
+static int tegra30_voltage_update(struct tegra_regulator_coupler *tegra,
+ struct regulator_dev *cpu_rdev,
+ struct regulator_dev *core_rdev)
+{
+ int core_min_uV, core_max_uV = INT_MAX;
+ int cpu_min_uV, cpu_max_uV = INT_MAX;
+ int cpu_min_uV_consumers = 0;
+ int core_min_limited_uV;
+ int core_target_uV;
+ int cpu_target_uV;
+ int core_max_step;
+ int cpu_max_step;
+ int max_spread;
+ int core_uV;
+ int cpu_uV;
+ int err;
+
+ /*
+ * CPU voltage should not got lower than 300mV from the CORE.
+ * CPU voltage should stay below the CORE by 100mV+, depending
+ * by the CORE voltage. This applies to all Tegra30 SoC's.
+ */
+ max_spread = cpu_rdev->constraints->max_spread[0];
+ cpu_max_step = cpu_rdev->constraints->max_uV_step;
+ core_max_step = core_rdev->constraints->max_uV_step;
+
+ if (!max_spread) {
+ pr_err_once("cpu-core max-spread is undefined in device-tree\n");
+ max_spread = 300000;
+ }
+
+ if (!cpu_max_step) {
+ pr_err_once("cpu max-step is undefined in device-tree\n");
+ cpu_max_step = 150000;
+ }
+
+ if (!core_max_step) {
+ pr_err_once("core max-step is undefined in device-tree\n");
+ core_max_step = 150000;
+ }
+
+ /*
+ * The CORE voltage scaling is currently not hooked up in drivers,
+ * hence we will limit the minimum CORE voltage to a reasonable value.
+ * This should be good enough for the time being.
+ */
+ core_min_uV = tegra30_core_limit(tegra, core_rdev);
+ if (core_min_uV < 0)
+ return core_min_uV;
+
+ err = regulator_check_consumers(core_rdev, &core_min_uV, &core_max_uV,
+ PM_SUSPEND_ON);
+ if (err)
+ return err;
+
+ core_uV = regulator_get_voltage_rdev(core_rdev);
+ if (core_uV < 0)
+ return core_uV;
+
+ cpu_min_uV = core_min_uV - max_spread;
+
+ err = regulator_check_consumers(cpu_rdev, &cpu_min_uV, &cpu_max_uV,
+ PM_SUSPEND_ON);
+ if (err)
+ return err;
+
+ err = regulator_check_consumers(cpu_rdev, &cpu_min_uV_consumers,
+ &cpu_max_uV, PM_SUSPEND_ON);
+ if (err)
+ return err;
+
+ err = regulator_check_voltage(cpu_rdev, &cpu_min_uV, &cpu_max_uV);
+ if (err)
+ return err;
+
+ cpu_uV = regulator_get_voltage_rdev(cpu_rdev);
+ if (cpu_uV < 0)
+ return 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
+ * survive the voltage drop if it's running on a higher frequency.
+ */
+ if (!cpu_min_uV_consumers)
+ cpu_min_uV = cpu_uV;
+
+ /*
+ * Bootloader shall set up voltages correctly, but if it
+ * happens that there is a violation, then try to fix it
+ * at first.
+ */
+ core_min_limited_uV = tegra30_core_cpu_limit(cpu_uV);
+ if (core_min_limited_uV < 0)
+ return core_min_limited_uV;
+
+ core_min_uV = max(core_min_uV, tegra30_core_cpu_limit(cpu_min_uV));
+
+ err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
+ if (err)
+ return err;
+
+ 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);
+ goto update_core;
+ }
+
+ while (cpu_uV != cpu_min_uV || core_uV != core_min_uV) {
+ if (cpu_uV < cpu_min_uV) {
+ cpu_target_uV = min(cpu_uV + cpu_max_step, cpu_min_uV);
+ } else {
+ cpu_target_uV = max(cpu_uV - cpu_max_step, cpu_min_uV);
+ cpu_target_uV = max(core_uV - max_spread, cpu_target_uV);
+ }
+
+ err = regulator_set_voltage_rdev(cpu_rdev,
+ cpu_target_uV,
+ cpu_max_uV,
+ PM_SUSPEND_ON);
+ if (err)
+ return err;
+
+ cpu_uV = cpu_target_uV;
+update_core:
+ core_min_limited_uV = tegra30_core_cpu_limit(cpu_uV);
+ if (core_min_limited_uV < 0)
+ return core_min_limited_uV;
+
+ core_target_uV = max(core_min_limited_uV, core_min_uV);
+
+ if (core_uV < core_target_uV) {
+ core_target_uV = min(core_target_uV, core_uV + core_max_step);
+ core_target_uV = min(core_target_uV, cpu_uV + max_spread);
+ } else {
+ core_target_uV = max(core_target_uV, core_uV - core_max_step);
+ }
+
+ err = regulator_set_voltage_rdev(core_rdev,
+ core_target_uV,
+ core_max_uV,
+ PM_SUSPEND_ON);
+ if (err)
+ return err;
+
+ core_uV = core_target_uV;
+ }
+
+ return 0;
+}
+
+static int tegra30_regulator_balance_voltage(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev,
+ suspend_state_t state)
+{
+ struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
+ struct regulator_dev *core_rdev = tegra->core_rdev;
+ struct regulator_dev *cpu_rdev = tegra->cpu_rdev;
+
+ if ((core_rdev != rdev && cpu_rdev != rdev) || state != PM_SUSPEND_ON) {
+ pr_err("regulators are not coupled properly\n");
+ return -EINVAL;
+ }
+
+ return tegra30_voltage_update(tegra, cpu_rdev, core_rdev);
+}
+
+static int tegra30_regulator_attach(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev)
+{
+ struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
+ struct device_node *np = rdev->dev.of_node;
+
+ if (of_property_read_bool(np, "nvidia,tegra-core-regulator") &&
+ !tegra->core_rdev) {
+ tegra->core_rdev = rdev;
+ return 0;
+ }
+
+ if (of_property_read_bool(np, "nvidia,tegra-cpu-regulator") &&
+ !tegra->cpu_rdev) {
+ tegra->cpu_rdev = rdev;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+static int tegra30_regulator_detach(struct regulator_coupler *coupler,
+ struct regulator_dev *rdev)
+{
+ struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
+
+ if (tegra->core_rdev == rdev) {
+ tegra->core_rdev = NULL;
+ return 0;
+ }
+
+ if (tegra->cpu_rdev == rdev) {
+ tegra->cpu_rdev = NULL;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+static struct tegra_regulator_coupler tegra30_coupler = {
+ .coupler = {
+ .attach_regulator = tegra30_regulator_attach,
+ .detach_regulator = tegra30_regulator_detach,
+ .balance_voltage = tegra30_regulator_balance_voltage,
+ },
+};
+
+static int __init tegra_regulator_coupler_init(void)
+{
+ if (!of_machine_is_compatible("nvidia,tegra30"))
+ return 0;
+
+ return regulator_coupler_register(&tegra30_coupler.coupler);
+}
+arch_initcall(tegra_regulator_coupler_init);
--
2.22.0