[PATCH v1 18/30] pwm: tegra: Support OPP and core voltage scaling

Dmitry Osipenko
2020-11-04T23:48:04Z

Add OPP and SoC core voltage scaling support to the Tegra PWM driver.
This is required for enabling system-wide DVFS on older Tegra SoCs.

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/pwm/Kconfig | 1 +
drivers/pwm/pwm-tegra.c | 84 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 82 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 63be5362fd3a..61d35ef759f2 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -509,6 +509,7 @@ config PWM_SUN4I
config PWM_TEGRA
tristate "NVIDIA Tegra PWM support"
depends on ARCH_TEGRA || COMPILE_TEST
+ select PM_OPP
help
Generic PWM framework driver for the PWFM controller found on NVIDIA
Tegra SoCs.
diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
index 1daf591025c0..96c253127ff3 100644
--- a/drivers/pwm/pwm-tegra.c
+++ b/drivers/pwm/pwm-tegra.c
@@ -42,12 +42,15 @@
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
+#include <linux/pm_opp.h>
#include <linux/pwm.h>
#include <linux/platform_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/slab.h>
#include <linux/reset.h>

+#include <soc/tegra/common.h>
+
#define PWM_ENABLE (1 << 31)
#define PWM_DUTY_WIDTH 8
#define PWM_DUTY_SHIFT 16
@@ -145,7 +148,7 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
required_clk_rate =
(NSEC_PER_SEC / period_ns) << PWM_DUTY_WIDTH;

- err = clk_set_rate(pc->clk, required_clk_rate);
+ err = dev_pm_opp_set_rate(pc->dev, required_clk_rate);
if (err < 0)
return -EINVAL;

@@ -181,6 +184,10 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
* before writing the register. Otherwise, keep it enabled.
*/
if (!pwm_is_enabled(pwm)) {
+ err = dev_pm_opp_set_rate(pc->dev, pc->clk_rate);
+ if (err < 0)
+ return err;
+
err = clk_prepare_enable(pc->clk);
if (err < 0)
return err;
@@ -191,9 +198,12 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,

/*
* If the PWM is not enabled, turn the clock off again to save power.
+ * Remove OPP performance/voltage vote after disabling the clock.
*/
- if (!pwm_is_enabled(pwm))
+ if (!pwm_is_enabled(pwm)) {
clk_disable_unprepare(pc->clk);
+ dev_pm_opp_set_rate(pc->dev, 0);
+ }

return 0;
}
@@ -204,6 +214,10 @@ static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
int rc = 0;
u32 val;

+ rc = dev_pm_opp_set_rate(pc->dev, pc->clk_rate);
+ if (rc < 0)
+ return rc;
+
rc = clk_prepare_enable(pc->clk);
if (rc < 0)
return rc;
@@ -225,6 +239,7 @@ static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
pwm_writel(pc, pwm->hwpwm, val);

clk_disable_unprepare(pc->clk);
+ dev_pm_opp_set_rate(pc->dev, 0);
}

static const struct pwm_ops tegra_pwm_ops = {
@@ -234,6 +249,60 @@ static const struct pwm_ops tegra_pwm_ops = {
.owner = THIS_MODULE,
};

+static void tegra_pwm_deinit_opp_table(void *data)
+{
+ struct device *dev = data;
+ struct opp_table *opp_table;
+
+ opp_table = dev_pm_opp_get_opp_table(dev);
+ dev_pm_opp_of_remove_table(dev);
+ dev_pm_opp_put_regulators(opp_table);
+ dev_pm_opp_put_opp_table(opp_table);
+}
+
+static int devm_tegra_pwm_init_opp_table(struct device *dev)
+{
+ struct opp_table *opp_table;
+ const char *rname = "core";
+ int err;
+
+ /* voltage scaling is optional */
+ if (device_property_present(dev, "core-supply"))
+ opp_table = dev_pm_opp_set_regulators(dev, &rname, 1);
+ else
+ opp_table = dev_pm_opp_get_opp_table(dev);
+
+ if (IS_ERR(opp_table))
+ return dev_err_probe(dev, PTR_ERR(opp_table),
+ "failed to prepare OPP table\n");
+
+ /*
+ * OPP table presence is optional and we want the set_rate() of OPP
+ * API to work similarly to clk_set_rate() if table is missing in a
+ * device-tree. The add_table() errors out if OPP is missing in DT.
+ */
+ if (device_property_present(dev, "operating-points-v2")) {
+ err = dev_pm_opp_of_add_table(dev);
+ if (err) {
+ dev_err(dev, "failed to add OPP table: %d\n", err);
+ goto put_table;
+ }
+ }
+
+ err = devm_add_action(dev, tegra_pwm_deinit_opp_table, dev);
+ if (err)
+ goto remove_table;
+
+ return 0;
+
+remove_table:
+ dev_pm_opp_of_remove_table(dev);
+put_table:
+ dev_pm_opp_put_regulators(opp_table);
+
+ return err;
+}
+
static int tegra_pwm_probe(struct platform_device *pdev)
{
struct tegra_pwm_chip *pwm;
@@ -258,8 +327,12 @@ static int tegra_pwm_probe(struct platform_device *pdev)
if (IS_ERR(pwm->clk))
return PTR_ERR(pwm->clk);

+ ret = devm_tegra_pwm_init_opp_table(&pdev->dev);
+ if (ret)
+ return ret;
+
/* Set maximum frequency of the IP */
- ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
+ ret = dev_pm_opp_set_rate(pwm->dev, pwm->soc->max_frequency);
if (ret < 0) {
dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
return ret;
@@ -309,6 +382,10 @@ static int tegra_pwm_remove(struct platform_device *pdev)
if (WARN_ON(!pc))
return -ENODEV;

+ err = dev_pm_opp_set_rate(pc->dev, pc->clk_rate);
+ if (err < 0)
+ return err;
+
err = clk_prepare_enable(pc->clk);
if (err < 0)
return err;
@@ -375,6 +452,7 @@ static struct platform_driver tegra_pwm_driver = {
.name = "tegra-pwm",
.of_match_table = tegra_pwm_of_match,
.pm = &tegra_pwm_pm_ops,
+ .sync_state = tegra_soc_device_sync_state,
},
.probe = tegra_pwm_probe,
.remove = tegra_pwm_remove,
--
2.27.0