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Subject[PATCH v3 1/1] pwm: pca9685: fix gpio-only operation.
Date
gpio-only driver operation never clears the SLEEP bit, which can
cause the gpios to become unusable.

Example:
1. user requests first pwm -> driver clears SLEEP bit
2. user frees last pwm -> driver sets SLEEP bit
3. user requests gpio
4. user switches gpio on -> output does not turn on
because SLEEP bit is set

Prevent this behaviour by letting the runtime_pm framework
control the SLEEP bit. This will put the chip to SLEEP if
no pwms/gpios are exported/in use.

Fixes: bccec89f0a35 ("Allow any of the 16 PWMs to be used as a GPIO")
Reported-by: Sven Van Asbroeck <TheSven73@googlemail.com>
Signed-off-by: Sven Van Asbroeck <TheSven73@googlemail.com>
Suggested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
drivers/pwm/pwm-pca9685.c | 111 ++++++++++++++++++++++++++++++++--------------
1 file changed, 78 insertions(+), 33 deletions(-)

diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 0cfb357..f4c422a 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -30,6 +30,7 @@
#include <linux/regmap.h>
#include <linux/slab.h>
#include <linux/delay.h>
+#include <linux/pm_runtime.h>

/*
* Because the PCA9685 has only one prescaler per chip, changing the period of
@@ -79,7 +80,6 @@
struct pca9685 {
struct pwm_chip chip;
struct regmap *regmap;
- int active_cnt;
int duty_ns;
int period_ns;
#if IS_ENABLED(CONFIG_GPIOLIB)
@@ -111,20 +111,10 @@ static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset)
pwm_set_chip_data(pwm, (void *)1);

mutex_unlock(&pca->lock);
+ pm_runtime_get_sync(pca->chip.dev);
return 0;
}

-static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset)
-{
- struct pca9685 *pca = gpiochip_get_data(gpio);
- struct pwm_device *pwm;
-
- mutex_lock(&pca->lock);
- pwm = &pca->chip.pwms[offset];
- pwm_set_chip_data(pwm, NULL);
- mutex_unlock(&pca->lock);
-}
-
static bool pca9685_pwm_is_gpio(struct pca9685 *pca, struct pwm_device *pwm)
{
bool is_gpio = false;
@@ -177,6 +167,19 @@ static void pca9685_pwm_gpio_set(struct gpio_chip *gpio, unsigned int offset,
regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), on);
}

+static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset)
+{
+ struct pca9685 *pca = gpiochip_get_data(gpio);
+ struct pwm_device *pwm;
+
+ pca9685_pwm_gpio_set(gpio, offset, 0);
+ pm_runtime_put(pca->chip.dev);
+ mutex_lock(&pca->lock);
+ pwm = &pca->chip.pwms[offset];
+ pwm_set_chip_data(pwm, NULL);
+ mutex_unlock(&pca->lock);
+}
+
static int pca9685_pwm_gpio_get_direction(struct gpio_chip *chip,
unsigned int offset)
{
@@ -238,6 +241,16 @@ static inline int pca9685_pwm_gpio_probe(struct pca9685 *pca)
}
#endif

+static void pca9685_set_sleep_mode(struct pca9685 *pca, int sleep)
+{
+ regmap_update_bits(pca->regmap, PCA9685_MODE1,
+ MODE1_SLEEP, sleep ? MODE1_SLEEP : 0);
+ if (!sleep) {
+ /* Wait 500us for the oscillator to be back up */
+ udelay(500);
+ }
+}
+
static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
@@ -252,19 +265,20 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,

if (prescale >= PCA9685_PRESCALE_MIN &&
prescale <= PCA9685_PRESCALE_MAX) {
+ /*
+ * putting the chip briefly into SLEEP mode
+ * at this point won't interfere with the
+ * pm_runtime framework, because the pm_runtime
+ * state is guaranteed active here.
+ */
/* Put chip into sleep mode */
- regmap_update_bits(pca->regmap, PCA9685_MODE1,
- MODE1_SLEEP, MODE1_SLEEP);
+ pca9685_set_sleep_mode(pca, 1);

/* Change the chip-wide output frequency */
regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);

/* Wake the chip up */
- regmap_update_bits(pca->regmap, PCA9685_MODE1,
- MODE1_SLEEP, 0x0);
-
- /* Wait 500us for the oscillator to be back up */
- udelay(500);
+ pca9685_set_sleep_mode(pca, 0);

pca->period_ns = period_ns;
} else {
@@ -406,21 +420,15 @@ static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)

if (pca9685_pwm_is_gpio(pca, pwm))
return -EBUSY;
-
- if (pca->active_cnt++ == 0)
- return regmap_update_bits(pca->regmap, PCA9685_MODE1,
- MODE1_SLEEP, 0x0);
+ pm_runtime_get_sync(chip->dev);

return 0;
}

static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
- struct pca9685 *pca = to_pca(chip);
-
- if (--pca->active_cnt == 0)
- regmap_update_bits(pca->regmap, PCA9685_MODE1, MODE1_SLEEP,
- MODE1_SLEEP);
+ pca9685_pwm_disable(chip, pwm);
+ pm_runtime_put(chip->dev);
}

static const struct pwm_ops pca9685_pwm_ops = {
@@ -492,21 +500,52 @@ static int pca9685_pwm_probe(struct i2c_client *client,
return ret;

ret = pca9685_pwm_gpio_probe(pca);
- if (ret < 0)
+ if (ret < 0) {
pwmchip_remove(&pca->chip);
+ return ret;
+ }

- return ret;
+ /* the chip comes out of power-up in the active state */
+ pm_runtime_set_active(&client->dev);
+ /* enable will put the chip into suspend, which is what we
+ * want as all outputs are disabled at this point
+ */
+ pm_runtime_enable(&client->dev);
+
+ return 0;
}

static int pca9685_pwm_remove(struct i2c_client *client)
{
struct pca9685 *pca = i2c_get_clientdata(client);
+ int ret;
+
+ ret = pwmchip_remove(&pca->chip);
+ if (ret)
+ return ret;
+ pm_runtime_disable(&client->dev);
+ return 0;
+}
+
+#ifdef CONFIG_PM
+static int pca9685_pwm_runtime_suspend(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct pca9685 *pca = i2c_get_clientdata(client);

- regmap_update_bits(pca->regmap, PCA9685_MODE1, MODE1_SLEEP,
- MODE1_SLEEP);
+ pca9685_set_sleep_mode(pca, 1);
+ return 0;
+}

- return pwmchip_remove(&pca->chip);
+static int pca9685_pwm_runtime_resume(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct pca9685 *pca = i2c_get_clientdata(client);
+
+ pca9685_set_sleep_mode(pca, 0);
+ return 0;
}
+#endif

static const struct i2c_device_id pca9685_id[] = {
{ "pca9685", 0 },
@@ -530,11 +569,17 @@ static int pca9685_pwm_remove(struct i2c_client *client)
MODULE_DEVICE_TABLE(of, pca9685_dt_ids);
#endif

+static const struct dev_pm_ops pca9685_pwm_pm = {
+ SET_RUNTIME_PM_OPS(pca9685_pwm_runtime_suspend,
+ pca9685_pwm_runtime_resume, NULL)
+};
+
static struct i2c_driver pca9685_i2c_driver = {
.driver = {
.name = "pca9685-pwm",
.acpi_match_table = ACPI_PTR(pca9685_acpi_ids),
.of_match_table = of_match_ptr(pca9685_dt_ids),
+ .pm = &pca9685_pwm_pm,
},
.probe = pca9685_pwm_probe,
.remove = pca9685_pwm_remove,
--
1.9.1
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