[PATCH v4 0/1] pwm: pca9685: fix gpio-only operation.

[PATCH v4 0/1] pwm: pca9685: fix gpio-only operation.

[Sven Van Asbroeck]

v4:
	fix coding style for multi-line comment
	added Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

v3:
	remove unnecessary call to pm_runtime_suspend()

	fix coding style for multi-line comment
	(checkpatch.pl should ideally catch this, but did not?)

v2:
	the pm_runtime framework controls the SLEEP bit, as suggested by
	Mika Westerberg.

v1:
	the SLEEP bit is always on.

Sven Van Asbroeck (1):
  pwm: pca9685: fix gpio-only operation.

 drivers/pwm/pwm-pca9685.c | 112 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 79 insertions(+), 33 deletions(-)

-- 
1.9.1

[PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Sven Van Asbroeck]

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>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/pwm/pwm-pca9685.c | 112 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 79 insertions(+), 33 deletions(-)

diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 0cfb357..5f55cfa 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 = {
@@ -492,22 +500,54 @@ 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;
+	}
+
+	/* 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 ret;
+	return 0;
 }
 
 static int pca9685_pwm_remove(struct i2c_client *client)
 {
 	struct pca9685 *pca = i2c_get_clientdata(client);
+	int ret;
 
-	regmap_update_bits(pca->regmap, PCA9685_MODE1, MODE1_SLEEP,
-			   MODE1_SLEEP);
+	ret = pwmchip_remove(&pca->chip);
+	if (ret)
+		return ret;
+	pm_runtime_disable(&client->dev);
+	return 0;
+}
 
-	return pwmchip_remove(&pca->chip);
+#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);
+
+	pca9685_set_sleep_mode(pca, 1);
+	return 0;
 }
 
+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 },
 	{ /* sentinel */ },
@@ -530,11 +570,17 @@ 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

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Thierry Reding]

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On Thu, Apr 13, 2017 at 08:58:11AM -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.
> 
> 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>
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> ---
>  drivers/pwm/pwm-pca9685.c | 112 ++++++++++++++++++++++++++++++++--------------
>  1 file changed, 79 insertions(+), 33 deletions(-)

Applied with s/gpio/GPIO/ and s/pwm/PWM/.

Thanks,
Thierry

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Andy Shevchenko]

+Cc: Rafael (one question to you below)

On Thu, 2017-04-13 at 08:58 -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.
> 

I know the patch is applied already, though please consider below to be
addressed as usual (w/o Fixes tag).

> +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);
> +	}

I would go with

/* Wait for @sleep microseconds for the oscillator to be back up */
if (sleep)
 udelay(sleep);

Otherwise int sleep is oddly here.

Or

bool sleep

/* Wait 500us ... */
if (sleep)
 udelay(500);

> +}


> +#ifdef CONFIG_PM
> +static int pca9685_pwm_runtime_suspend(struct device *dev)

__maybe_unused and remove ugly #ifdef:ery.

> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct pca9685 *pca = i2c_get_clientdata(client);
> +
> +	pca9685_set_sleep_mode(pca, 1);
> +	return 0;
>  }
>  
> +static int pca9685_pwm_runtime_resume(struct device *dev)

Ditto.

> +{
> +	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 dev_pm_ops pca9685_pwm_pm = {
> +	SET_RUNTIME_PM_OPS(pca9685_pwm_runtime_suspend,
> +			   pca9685_pwm_runtime_resume, NULL)
> +};
> +

Perhaps we may introduce RUNTIME_DEV_PM_OPS() macro and re-use it here.
Rafael?

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Sven Van Asbroeck]

Thanks for the feedback Andy !!

> I would go with
>
> /* Wait for @sleep microseconds for the oscillator to be back up */
> if (sleep)
>  udelay(sleep);
>
> Otherwise int sleep is oddly here.
>
> Or
>
> bool sleep
>
> /* Wait 500us ... */
> if (sleep)
>  udelay(500);
>
>> +}

I think you may be getting confused between:
- the chip's SLEEP bit (int sleep)
- the amount of time to delay after chip comes _out of_ sleep.
(always 500 us)

If it's confusing for you, it might be confusing for others?
Perhaps change the parameter to 'bool sleep_bit' or 'bool do_sleep'
to make the distinction clearer?

> __maybe_unused and remove ugly #ifdef:ery.

If this works on non- CONFIG_PM systems, I'm all for it !
Grepping the drivers/ directory, I see that some drivers use
#ifdef CONFIG_PM, some use __maybe_unused for runtime_pm.

Mika and Thierry, thoughts ?

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Mika Westerberg]

On Tue, Apr 18, 2017 at 11:52:49AM -0400, Sven Van Asbroeck wrote:
> > __maybe_unused and remove ugly #ifdef:ery.
> 
> If this works on non- CONFIG_PM systems, I'm all for it !
> Grepping the drivers/ directory, I see that some drivers use
> #ifdef CONFIG_PM, some use __maybe_unused for runtime_pm.
> 
> Mika and Thierry, thoughts ?

I actually prefer CONFIG_PM here but up to Thierry to decide, I guess.

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Andy Shevchenko]

On Tue, Apr 18, 2017 at 6:52 PM, Sven Van Asbroeck <thesven73@gmail.com> wrote:
> Thanks for the feedback Andy !!

You're welcome.

>
>> I would go with
>>
>> /* Wait for @sleep microseconds for the oscillator to be back up */
>> if (sleep)
>>  udelay(sleep);
>>
>> Otherwise int sleep is oddly here.
>>
>> Or
>>
>> bool sleep
>>
>> /* Wait 500us ... */
>> if (sleep)
>>  udelay(500);
>>
>>> +}
>
> I think you may be getting confused between:
> - the chip's SLEEP bit (int sleep)
> - the amount of time to delay after chip comes _out of_ sleep.
> (always 500 us)
>
> If it's confusing for you, it might be confusing for others?
> Perhaps change the parameter to 'bool sleep_bit' or 'bool do_sleep'
> to make the distinction clearer?

Taking above into consideration perhaps sleep is not quite good word
at all. By functional description it sounds like latency tolerance to
me.

>> __maybe_unused and remove ugly #ifdef:ery.
>
> If this works on non- CONFIG_PM systems, I'm all for it !
> Grepping the drivers/ directory, I see that some drivers use
> #ifdef CONFIG_PM, some use __maybe_unused for runtime_pm.

This approach kinda new that's why you see variety of approaches.

> Mika and Thierry, thoughts ?

At the end it's Thierry's call, so, I'm not insisting.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Sven Van Asbroeck]

> Taking above into consideration perhaps sleep is not quite good word
> at all. By functional description it sounds like latency tolerance to
> me.

That's true, but the bit description in the chip datasheet is 'SLEEP'.
(its real function is suspend/low power, but the chip designers called
it 'SLEEP')

Calling the bit/function something else is likely to confuse someone
who's reading the driver in combination with the chip datasheet.

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Andy Shevchenko]

On Thu, Apr 20, 2017 at 5:12 PM, Sven Van Asbroeck <thesven73@gmail.com> wrote:
>> Taking above into consideration perhaps sleep is not quite good word
>> at all. By functional description it sounds like latency tolerance to
>> me.
>
> That's true, but the bit description in the chip datasheet is 'SLEEP'.
> (its real function is suspend/low power, but the chip designers called
> it 'SLEEP')
>
> Calling the bit/function something else is likely to confuse someone
> who's reading the driver in combination with the chip datasheet.

Looking again into the patch I have noticed:
1) word 'sleep' is used as a part of a function name;
2) int sleep is used as binary value.

Thus, I would suggest: int sleep -> bool enable (or alike).

Would we agree on that?
-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Sven Van Asbroeck]

> Thus, I would suggest: int sleep -> bool enable (or alike).
>
> Would we agree on that?

I would. Perhaps also:
set_sleep_mode(int sleep) -> enable_sleep_mode(bool enable) ?

Let's see what Mika and Thierry think.

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Mika Westerberg]

On Thu, Apr 20, 2017 at 06:07:37PM +0300, Andy Shevchenko wrote:
> On Thu, Apr 20, 2017 at 5:12 PM, Sven Van Asbroeck <thesven73@gmail.com> wrote:
> >> Taking above into consideration perhaps sleep is not quite good word
> >> at all. By functional description it sounds like latency tolerance to
> >> me.
> >
> > That's true, but the bit description in the chip datasheet is 'SLEEP'.
> > (its real function is suspend/low power, but the chip designers called
> > it 'SLEEP')
> >
> > Calling the bit/function something else is likely to confuse someone
> > who's reading the driver in combination with the chip datasheet.
> 
> Looking again into the patch I have noticed:
> 1) word 'sleep' is used as a part of a function name;
> 2) int sleep is used as binary value.
> 
> Thus, I would suggest: int sleep -> bool enable (or alike).
> 
> Would we agree on that?

That sounds good to me. I guess it will have to be an incremental patch
since this one has already been applied.

Re: [PATCH v4 1/1] pwm: pca9685: fix gpio-only operation.

[Andy Shevchenko]

On Thu, 2017-04-20 at 11:50 -0400, Sven Van Asbroeck wrote:
> > Thus, I would suggest: int sleep -> bool enable (or alike).
> > 
> > Would we agree on that?
> 
> I would. Perhaps also:
> set_sleep_mode(int sleep) -> enable_sleep_mode(bool enable) ?

I'm okay with a such (don't forget to change 0/1 in call sites to
false/true as well).

> Let's see what Mika and Thierry think.

I suppose Mika's answer is an acknowledge to the change.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy