diff mbox series

[v2,1/2] pwm: bcm-iproc: handle clk_get_rate() return

Message ID 20200323092424.22664-2-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, 9:24 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, 9:35 a.m. UTC | #1 
On Mon, Mar 23, 2020 at 02:54:23PM +0530, Rayagonda Kokatanur wrote:
> Handle clk_get_rate() returning <= 0 condition to avoid
> possible division by zero.

The idea I wanted to transport with my question about how this problem
was found is that the commit log is amended with this information. This
is important information as it helps people having to decide if this
change should be backported. Also it would be great to know if this can
really make the kernel crash or if (e.g.) said clock cannot be off in
practise.

Best regards
Uwe
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,