diff mbox series

[v1,1/2] pwm: bcm-iproc: handle clk_get_rate() return

Message ID 20200323065318.16533-2-rayagonda.kokatanur@broadcom.com (mailing list archive)
State New, archived
Headers show
Series Handle return value and remove unnecessary check | expand

Commit Message

Rayagonda Kokatanur March 23, 2020, 6:53 a.m. UTC 
Handle clk_get_rate() returning <= 0 condition to avoid
possible division by zero.

Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
---
 drivers/pwm/pwm-bcm-iproc.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

Comments

Uwe Kleine-König March 23, 2020, 8:25 a.m. UTC | #1 
On Mon, Mar 23, 2020 at 12:23:17PM +0530, Rayagonda Kokatanur wrote:
> Handle clk_get_rate() returning <= 0 condition to avoid
> possible division by zero.

Was this noticed during a review and is more theoretic. Or does this
(depending on pre-boot state) result in a kernel crash?

> Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
> Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
> ---
>  drivers/pwm/pwm-bcm-iproc.c | 32 +++++++++++++++++++-------------
>  1 file changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
> index 1f829edd8ee7..8bbd2a04fead 100644
> --- a/drivers/pwm/pwm-bcm-iproc.c
> +++ b/drivers/pwm/pwm-bcm-iproc.c
> @@ -99,19 +99,25 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>  	else
>  		state->polarity = PWM_POLARITY_INVERSED;
>  
> -	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> -	prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
> -	prescale &= IPROC_PWM_PRESCALE_MAX;
> -
> -	multi = NSEC_PER_SEC * (prescale + 1);
> -
> -	value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
> -	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> -	state->period = div64_u64(tmp, rate);
> -
> -	value = readl(ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
> -	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> -	state->duty_cycle = div64_u64(tmp, rate);
> +	if (rate == 0) {
> +		state->period = 0;
> +		state->duty_cycle = 0;
> +	} else {
> +		value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> +		prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
> +		prescale &= IPROC_PWM_PRESCALE_MAX;
> +
> +		multi = NSEC_PER_SEC * (prescale + 1);
> +
> +		value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
> +		tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> +		state->period = div64_u64(tmp, rate);
> +
> +		value = readl(ip->base +
> +			      IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
> +		tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> +		state->duty_cycle = div64_u64(tmp, rate);
> +	}

The change looks fine.

Best regards
Uwe
Rayagonda Kokatanur March 23, 2020, 9:05 a.m. UTC | #2 
On Mon, Mar 23, 2020 at 1:55 PM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
>
> On Mon, Mar 23, 2020 at 12:23:17PM +0530, Rayagonda Kokatanur wrote:
> > Handle clk_get_rate() returning <= 0 condition to avoid
> > possible division by zero.
>
> Was this noticed during a review and is more theoretic. Or does this
> (depending on pre-boot state) result in a kernel crash?

This is reported by internal coverity tool.
>
> > Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
> > Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
> > ---
> >  drivers/pwm/pwm-bcm-iproc.c | 32 +++++++++++++++++++-------------
> >  1 file changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
> > index 1f829edd8ee7..8bbd2a04fead 100644
> > --- a/drivers/pwm/pwm-bcm-iproc.c
> > +++ b/drivers/pwm/pwm-bcm-iproc.c
> > @@ -99,19 +99,25 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> >       else
> >               state->polarity = PWM_POLARITY_INVERSED;
> >
> > -     value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> > -     prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
> > -     prescale &= IPROC_PWM_PRESCALE_MAX;
> > -
> > -     multi = NSEC_PER_SEC * (prescale + 1);
> > -
> > -     value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
> > -     tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> > -     state->period = div64_u64(tmp, rate);
> > -
> > -     value = readl(ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
> > -     tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> > -     state->duty_cycle = div64_u64(tmp, rate);
> > +     if (rate == 0) {
> > +             state->period = 0;
> > +             state->duty_cycle = 0;
> > +     } else {
> > +             value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> > +             prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
> > +             prescale &= IPROC_PWM_PRESCALE_MAX;
> > +
> > +             multi = NSEC_PER_SEC * (prescale + 1);
> > +
> > +             value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
> > +             tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> > +             state->period = div64_u64(tmp, rate);
> > +
> > +             value = readl(ip->base +
> > +                           IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
> > +             tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
> > +             state->duty_cycle = div64_u64(tmp, rate);
> > +     }
>
> The change looks fine.
>
> Best regards
> Uwe
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | https://www.pengutronix.de/ |
diff mbox series

Patch

diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
index 1f829edd8ee7..8bbd2a04fead 100644
--- a/drivers/pwm/pwm-bcm-iproc.c
+++ b/drivers/pwm/pwm-bcm-iproc.c
@@ -99,19 +99,25 @@  static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	else
 		state->polarity = PWM_POLARITY_INVERSED;
 
-	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
-	prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
-	prescale &= IPROC_PWM_PRESCALE_MAX;
-
-	multi = NSEC_PER_SEC * (prescale + 1);
-
-	value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
-	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
-	state->period = div64_u64(tmp, rate);
-
-	value = readl(ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
-	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
-	state->duty_cycle = div64_u64(tmp, rate);
+	if (rate == 0) {
+		state->period = 0;
+		state->duty_cycle = 0;
+	} else {
+		value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
+		prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
+		prescale &= IPROC_PWM_PRESCALE_MAX;
+
+		multi = NSEC_PER_SEC * (prescale + 1);
+
+		value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
+		tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
+		state->period = div64_u64(tmp, rate);
+
+		value = readl(ip->base +
+			      IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
+		tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
+		state->duty_cycle = div64_u64(tmp, rate);
+	}
 }
 
 static int iproc_pwmc_apply(struct pwm_chip *chip, struct pwm_device *pwm,