pwm: lpss: Add pwm_lpss_prepare_enable() helper

In the not-enabled -> enabled path pwm_lpss_apply() needs to get a
runtime-pm reference; and then on any errors it needs to release it
again.

This leads to somewhat hard to read code. This commit introduces a new
pwm_lpss_prepare_enable() helper and moves all the steps necessary for
the not-enabled -> enabled transition there, so that we can error check
the entire transition in a single place and only have one pm_runtime_put()
on failure call site.

While working on this I noticed that the enabled -> enabled (update
settings) path was quite similar, so I've added an enable parameter to
the new pwm_lpss_prepare_enable() helper, which allows using it in that
path too.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200903112337.4113-6-hdegoede@redhat.com

drivers/pwm/pwm-lpss.c

@@ -122,41 +122,48 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 		pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
 }
 
+static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
+				   struct pwm_device *pwm,
+				   const struct pwm_state *state,
+				   bool enable)
+{
+	int ret;
+
+	ret = pwm_lpss_is_updating(pwm);
+	if (ret)
+		return ret;
+
+	pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
+	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == false);
+	ret = pwm_lpss_wait_for_update(pwm);
+	if (ret)
+		return ret;
+
+	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == true);
+	return 0;
+}
+
 static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			  const struct pwm_state *state)
 {
 	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
-	int ret;
+	int ret = 0;
 
 	if (state->enabled) {
 		if (!pwm_is_enabled(pwm)) {
 			pm_runtime_get_sync(chip->dev);
-			ret = pwm_lpss_is_updating(pwm);
-			if (ret) {
-				pm_runtime_put(chip->dev);
-				return ret;
-			}
-			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
-			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
-			ret = pwm_lpss_wait_for_update(pwm);
-			if (ret) {
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true);
+			if (ret)
 				pm_runtime_put(chip->dev);
-				return ret;
-			}
-			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
 		} else {
-			ret = pwm_lpss_is_updating(pwm);
-			if (ret)
-				return ret;
-			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
-			return pwm_lpss_wait_for_update(pwm);
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false);
 		}
 	} else if (pwm_is_enabled(pwm)) {
 		pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
 		pm_runtime_put(chip->dev);
 	}
 
-	return 0;
+	return ret;
 }
 
 static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm,