[PATCH 5.10-stable] gpio: mvebu: fix pwm .get_state period calculation

[PATCH 5.10-stable] gpio: mvebu: fix pwm .get_state period calculation

[Baruch Siach]

commit e73b0101ae5124bf7cd3fb5d250302ad2f16a416 upstream.

The period is the sum of on and off values. That is, calculate period as

  ($on + $off) / clkrate

instead of

  $off / clkrate - $on / clkrate

that makes no sense.

Reported-by: Russell King <linux@armlinux.org.uk>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---

This backported patch applies to all kernels between 4.14 and 5.10
(inclusive).
---
 drivers/gpio/gpio-mvebu.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index 2f245594a90a..ed7c5fc47f52 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -660,9 +660,8 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
 
 	spin_lock_irqsave(&mvpwm->lock, flags);
 
-	val = (unsigned long long)
-		readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
-	val *= NSEC_PER_SEC;
+	u = readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
+	val = (unsigned long long) u * NSEC_PER_SEC;
 	do_div(val, mvpwm->clk_rate);
 	if (val > UINT_MAX)
 		state->duty_cycle = UINT_MAX;
@@ -671,21 +670,17 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->duty_cycle = 1;
 
-	val = (unsigned long long)
-		readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
+	val = (unsigned long long) u; /* on duration */
+	/* period = on + off duration */
+	val += readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
 	val *= NSEC_PER_SEC;
 	do_div(val, mvpwm->clk_rate);
-	if (val < state->duty_cycle) {
+	if (val > UINT_MAX)
+		state->period = UINT_MAX;
+	else if (val)
+		state->period = val;
+	else
 		state->period = 1;
-	} else {
-		val -= state->duty_cycle;
-		if (val > UINT_MAX)
-			state->period = UINT_MAX;
-		else if (val)
-			state->period = val;
-		else
-			state->period = 1;
-	}
 
 	regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u);
 	if (u)
-- 
2.29.2

Re: [PATCH 5.10-stable] gpio: mvebu: fix pwm .get_state period calculation

[Uwe Kleine-König]

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On Tue, Jan 26, 2021 at 11:00:11AM +0200, Baruch Siach wrote:
> commit e73b0101ae5124bf7cd3fb5d250302ad2f16a416 upstream.
> 
> The period is the sum of on and off values. That is, calculate period as
> 
>   ($on + $off) / clkrate
> 
> instead of
> 
>   $off / clkrate - $on / clkrate
> 
> that makes no sense.
> 
> Reported-by: Russell King <linux@armlinux.org.uk>
> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Doesn't this need something like:

	[baruch: Backported to 5.10]

plus a new S-o-B?

> ---
> 
> This backported patch applies to all kernels between 4.14 and 5.10
> (inclusive).
> ---
>  drivers/gpio/gpio-mvebu.c | 25 ++++++++++---------------
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
> index 2f245594a90a..ed7c5fc47f52 100644
> --- a/drivers/gpio/gpio-mvebu.c
> +++ b/drivers/gpio/gpio-mvebu.c
> @@ -660,9 +660,8 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
>  
>  	spin_lock_irqsave(&mvpwm->lock, flags);
>  
> -	val = (unsigned long long)
> -		readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
> -	val *= NSEC_PER_SEC;
> +	u = readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
> +	val = (unsigned long long) u * NSEC_PER_SEC;
>  	do_div(val, mvpwm->clk_rate);
>  	if (val > UINT_MAX)
>  		state->duty_cycle = UINT_MAX;
> @@ -671,21 +670,17 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
>  	else
>  		state->duty_cycle = 1;
>  
> -	val = (unsigned long long)
> -		readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
> +	val = (unsigned long long) u; /* on duration */
> +	/* period = on + off duration */
> +	val += readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
>  	val *= NSEC_PER_SEC;
>  	do_div(val, mvpwm->clk_rate);
> -	if (val < state->duty_cycle) {
> +	if (val > UINT_MAX)
> +		state->period = UINT_MAX;
> +	else if (val)
> +		state->period = val;
> +	else
>  		state->period = 1;
> -	} else {
> -		val -= state->duty_cycle;
> -		if (val > UINT_MAX)
> -			state->period = UINT_MAX;
> -		else if (val)
> -			state->period = val;
> -		else
> -			state->period = 1;
> -	}
>  
>  	regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u);
>  	if (u)

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH 5.10-stable] gpio: mvebu: fix pwm .get_state period calculation

[Baruch Siach]

Hi Uwe,

Thanks for your review.

On Tue, Jan 26 2021, Uwe Kleine-König wrote:
> On Tue, Jan 26, 2021 at 11:00:11AM +0200, Baruch Siach wrote:
>> commit e73b0101ae5124bf7cd3fb5d250302ad2f16a416 upstream.
>> 
>> The period is the sum of on and off values. That is, calculate period as
>> 
>>   ($on + $off) / clkrate
>> 
>> instead of
>> 
>>   $off / clkrate - $on / clkrate
>> 
>> that makes no sense.
>> 
>> Reported-by: Russell King <linux@armlinux.org.uk>
>> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
>> Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
>> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> Doesn't this need something like:
>
> 	[baruch: Backported to 5.10]
>
> plus a new S-o-B?

I could not find this requirement in the stable-kernel-rules.rst (Option
3) text.

Greg, should I resend the patch with another SoB?

Thanks,
baruch

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -

Re: [PATCH 5.10-stable] gpio: mvebu: fix pwm .get_state period calculation

[Greg Kroah-Hartman]

On Wed, Jan 27, 2021 at 03:06:55PM +0200, Baruch Siach wrote:
> Hi Uwe,
> 
> Thanks for your review.
> 
> On Tue, Jan 26 2021, Uwe Kleine-König wrote:
> > On Tue, Jan 26, 2021 at 11:00:11AM +0200, Baruch Siach wrote:
> >> commit e73b0101ae5124bf7cd3fb5d250302ad2f16a416 upstream.
> >> 
> >> The period is the sum of on and off values. That is, calculate period as
> >> 
> >>   ($on + $off) / clkrate
> >> 
> >> instead of
> >> 
> >>   $off / clkrate - $on / clkrate
> >> 
> >> that makes no sense.
> >> 
> >> Reported-by: Russell King <linux@armlinux.org.uk>
> >> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> >> Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
> >> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> >> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > Doesn't this need something like:
> >
> > 	[baruch: Backported to 5.10]
> >
> > plus a new S-o-B?
> 
> I could not find this requirement in the stable-kernel-rules.rst (Option
> 3) text.
> 
> Greg, should I resend the patch with another SoB?

Please do!

thanks,

greg k-h