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Message-ID: <20170412085350.GB29222@lahna.fi.intel.com>
Date: Wed, 12 Apr 2017 11:53:50 +0300
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Sven Van Asbroeck <thesven73@...il.com>
Cc: thierry.reding@...il.com, linux-pwm@...r.kernel.org,
linux-kernel@...r.kernel.org, clemens.gruber@...ruber.com,
andriy.shevchenko@...ux.intel.com,
Sven Van Asbroeck <TheSven73@...glemail.com>
Subject: Re: [PATCH v2 1/1] pwm: pca9685: fix gpio-only operation.
On Tue, Apr 11, 2017 at 03:19:05PM -0400, Sven Van Asbroeck wrote:
> 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.
Looks like going to the right direction. I have a couple of comments see
below.
>
> Fixes: bccec89f0a35 ("Allow any of the 16 PWMs to be used as a GPIO")
> Reported-by: Sven Van Asbroeck <TheSven73@...glemail.com>
> Signed-off-by: Sven Van Asbroeck <TheSven73@...glemail.com>
> Suggested-by: Mika Westerberg <mika.westerberg@...ux.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..465eb57 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);
> +}
Why did you move the function here?
> +
> 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 +265,19 @@ 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.
> + */
The comment style should follow the one in
Documentation/process/coding-style.rst.
> /* 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 +419,15 @@ 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 +499,53 @@ 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_suspend(&client->dev);
Is it necessary to call this?
In principle you need to undo whatever you did in ->probe() so calling
pm_runtime_set_suspended() here makes more sense IMHO.
You can try how it works if you load/unload the driver several times-.
> + 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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