diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 42ffd2e..df6f042 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -54,16 +54,18 @@
 static void sample_timer(struct timer_list *t)
 {
 	struct pwm_fan_ctx *ctx = from_timer(ctx, t, rpm_timer);
+	unsigned int delta = ktime_ms_delta(ktime_get(), ctx->sample_start);
 	int pulses;
-	u64 tmp;
 
-	pulses = atomic_read(&ctx->pulses);
-	atomic_sub(pulses, &ctx->pulses);
-	tmp = (u64)pulses * ktime_ms_delta(ktime_get(), ctx->sample_start) * 60;
-	do_div(tmp, ctx->pulses_per_revolution * 1000);
-	ctx->rpm = tmp;
+	if (delta) {
+		pulses = atomic_read(&ctx->pulses);
+		atomic_sub(pulses, &ctx->pulses);
+		ctx->rpm = (unsigned int)(pulses * 1000 * 60) /
+			(ctx->pulses_per_revolution * delta);
 
-	ctx->sample_start = ktime_get();
+		ctx->sample_start = ktime_get();
+	}
+
 	mod_timer(&ctx->rpm_timer, jiffies + HZ);
 }
 
@@ -328,8 +330,18 @@
 
 	ctx->pwm_value = MAX_PWM;
 
-	/* Set duty cycle to maximum allowed and enable PWM output */
 	pwm_init_state(ctx->pwm, &state);
+	/*
+	 * __set_pwm assumes that MAX_PWM * (period - 1) fits into an unsigned
+	 * long. Check this here to prevent the fan running at a too low
+	 * frequency.
+	 */
+	if (state.period > ULONG_MAX / MAX_PWM + 1) {
+		dev_err(dev, "Configured period too big\n");
+		return -EINVAL;
+	}
+
+	/* Set duty cycle to maximum allowed and enable PWM output */
 	state.duty_cycle = ctx->pwm->args.period - 1;
 	state.enabled = true;