pwm: sysfs: Add suspend/resume support

According to the Documentation/pwm.txt, all PWM consumers should have
power management. Since this sysfs interface is one of consumers so that
this patch adds suspend/resume support.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
[thierry.reding@gmail.com: fix build warnings for !PM]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/sysfs.c

@@ -27,6 +27,7 @@ struct pwm_export {
 	struct device child;
 	struct pwm_device *pwm;
 	struct mutex lock;
+	struct pwm_state suspend;
 };
 
 static struct pwm_export *child_to_pwm_export(struct device *child)
@@ -381,10 +382,111 @@ static struct attribute *pwm_chip_attrs[] = {
 };
 ATTRIBUTE_GROUPS(pwm_chip);
 
+/* takes export->lock on success */
+static struct pwm_export *pwm_class_get_state(struct device *parent,
+					      struct pwm_device *pwm,
+					      struct pwm_state *state)
+{
+	struct device *child;
+	struct pwm_export *export;
+
+	if (!test_bit(PWMF_EXPORTED, &pwm->flags))
+		return NULL;
+
+	child = device_find_child(parent, pwm, pwm_unexport_match);
+	if (!child)
+		return NULL;
+
+	export = child_to_pwm_export(child);
+	put_device(child);	/* for device_find_child() */
+
+	mutex_lock(&export->lock);
+	pwm_get_state(pwm, state);
+
+	return export;
+}
+
+static int pwm_class_apply_state(struct pwm_export *export,
+				 struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	int ret = pwm_apply_state(pwm, state);
+
+	/* release lock taken in pwm_class_get_state */
+	mutex_unlock(&export->lock);
+
+	return ret;
+}
+
+static int pwm_class_resume_npwm(struct device *parent, unsigned int npwm)
+{
+	struct pwm_chip *chip = dev_get_drvdata(parent);
+	unsigned int i;
+	int ret = 0;
+
+	for (i = 0; i < npwm; i++) {
+		struct pwm_device *pwm = &chip->pwms[i];
+		struct pwm_state state;
+		struct pwm_export *export;
+
+		export = pwm_class_get_state(parent, pwm, &state);
+		if (!export)
+			continue;
+
+		state.enabled = export->suspend.enabled;
+		ret = pwm_class_apply_state(export, pwm, &state);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+
+static int __maybe_unused pwm_class_suspend(struct device *parent)
+{
+	struct pwm_chip *chip = dev_get_drvdata(parent);
+	unsigned int i;
+	int ret = 0;
+
+	for (i = 0; i < chip->npwm; i++) {
+		struct pwm_device *pwm = &chip->pwms[i];
+		struct pwm_state state;
+		struct pwm_export *export;
+
+		export = pwm_class_get_state(parent, pwm, &state);
+		if (!export)
+			continue;
+
+		export->suspend = state;
+		state.enabled = false;
+		ret = pwm_class_apply_state(export, pwm, &state);
+		if (ret < 0) {
+			/*
+			 * roll back the PWM devices that were disabled by
+			 * this suspend function.
+			 */
+			pwm_class_resume_npwm(parent, i);
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static int __maybe_unused pwm_class_resume(struct device *parent)
+{
+	struct pwm_chip *chip = dev_get_drvdata(parent);
+
+	return pwm_class_resume_npwm(parent, chip->npwm);
+}
+
+static SIMPLE_DEV_PM_OPS(pwm_class_pm_ops, pwm_class_suspend, pwm_class_resume);
+
 static struct class pwm_class = {
 	.name = "pwm",
 	.owner = THIS_MODULE,
 	.dev_groups = pwm_chip_groups,
+	.pm = &pwm_class_pm_ops,
 };
 
 static int pwmchip_sysfs_match(struct device *parent, const void *data)