1 files changed, 16 insertions, 5 deletions

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index cc63f9baa481..16c70147ec40 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -43,7 +43,7 @@
 
 struct pwm_sifive_ddata {
 	struct pwm_chip	chip;
-	struct mutex lock; /* lock to protect user_count */
+	struct mutex lock; /* lock to protect user_count and approx_period */
 	struct notifier_block notifier;
 	struct clk *clk;
 	void __iomem *regs;
@@ -78,6 +78,7 @@ static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
 	mutex_unlock(&ddata->lock);
 }
 
+/* Called holding ddata->lock */
 static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
 				    unsigned long rate)
 {
@@ -166,7 +167,6 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 		return ret;
 	}
 
-	mutex_lock(&ddata->lock);
 	cur_state = pwm->state;
 	enabled = cur_state.enabled;
 
@@ -185,14 +185,23 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	/* The hardware cannot generate a 100% duty cycle */
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
 
+	mutex_lock(&ddata->lock);
 	if (state->period != ddata->approx_period) {
-		if (ddata->user_count != 1) {
+		/*
+		 * Don't let a 2nd user change the period underneath the 1st user.
+		 * However if ddate->approx_period == 0 this is the first time we set
+		 * any period, so let whoever gets here first set the period so other
+		 * users who agree on the period won't fail.
+		 */
+		if (ddata->user_count != 1 && ddata->approx_period) {
+			mutex_unlock(&ddata->lock);
 			ret = -EBUSY;
 			goto exit;
 		}
 		ddata->approx_period = state->period;
 		pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
 	}
+	mutex_unlock(&ddata->lock);
 
 	writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +
 	       pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
@@ -202,7 +211,6 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 exit:
 	clk_disable(ddata->clk);
-	mutex_unlock(&ddata->lock);
 	return ret;
 }
 
@@ -221,8 +229,11 @@ static int pwm_sifive_clock_notifier(struct notifier_block *nb,
 	struct pwm_sifive_ddata *ddata =
 		container_of(nb, struct pwm_sifive_ddata, notifier);
 
-	if (event == POST_RATE_CHANGE)
+	if (event == POST_RATE_CHANGE) {
+		mutex_lock(&ddata->lock);
 		pwm_sifive_update_clock(ddata, ndata->new_rate);
+		mutex_unlock(&ddata->lock);
+	}
 
 	return NOTIFY_OK;
 }