[PATCH v2] backlight: pwm_bl: switch to using "atomic" PWM API

[Enric Balletbo i Serra]

The "atomic" API allows us to configure PWM period and duty_cycle and
enable it in one call.

The patch also moves the pwm_init_state just before any use of the
pwm_state struct, this fixes a potential bug where pwm_get_state
can be called before pwm_init_state.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
---

Changes in v2:
- Do not force the PWM be off in the first call to pwm_apply_state.
- Delayed applying the state until we know what the period is.
- Removed pb->period as after the conversion is not needed.

 drivers/video/backlight/pwm_bl.c | 71 ++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 30 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index bdfcc0a71db1..dd1cb29b5332 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -28,7 +28,6 @@
 struct pwm_bl_data {
 	struct pwm_device	*pwm;
 	struct device		*dev;
-	unsigned int		period;
 	unsigned int		lth_brightness;
 	unsigned int		*levels;
 	bool			enabled;
@@ -46,7 +45,8 @@ struct pwm_bl_data {
 	void			(*exit)(struct device *);
 };
 
-static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
+static void pwm_backlight_power_on(struct pwm_bl_data *pb,
+				   struct pwm_state *state)
 {
 	int err;
 
@@ -57,7 +57,8 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 	if (err < 0)
 		dev_err(pb->dev, "failed to enable power supply\n");
 
-	pwm_enable(pb->pwm);
+	state->enabled = true;
+	pwm_apply_state(pb->pwm, state);
 
 	if (pb->post_pwm_on_delay)
 		msleep(pb->post_pwm_on_delay);
@@ -70,6 +71,8 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 
 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 {
+	struct pwm_state state;
+
 	if (!pb->enabled)
 		return;
 
@@ -79,8 +82,10 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 	if (pb->pwm_off_delay)
 		msleep(pb->pwm_off_delay);
 
-	pwm_config(pb->pwm, 0, pb->period);
-	pwm_disable(pb->pwm);
+	pwm_get_state(pb->pwm, &state);
+	state.enabled = false;
+	state.duty_cycle = 0;
+	pwm_apply_state(pb->pwm, &state);
 
 	regulator_disable(pb->power_supply);
 	pb->enabled = false;
@@ -89,14 +94,17 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
 {
 	unsigned int lth = pb->lth_brightness;
+	struct pwm_state state;
 	u64 duty_cycle;
 
+	pwm_get_state(pb->pwm, &state);
+
 	if (pb->levels)
 		duty_cycle = pb->levels[brightness];
 	else
 		duty_cycle = brightness;
 
-	duty_cycle *= pb->period - lth;
+	duty_cycle *= state.period - lth;
 	do_div(duty_cycle, pb->scale);
 
 	return duty_cycle + lth;
@@ -106,6 +114,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 {
 	struct pwm_bl_data *pb = bl_get_data(bl);
 	int brightness = bl->props.brightness;
+	struct pwm_state state;
 	int duty_cycle;
 
 	if (bl->props.power != FB_BLANK_UNBLANK ||
@@ -118,8 +127,12 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 
 	if (brightness > 0) {
 		duty_cycle = compute_duty_cycle(pb, brightness);
-		pwm_config(pb->pwm, duty_cycle, pb->period);
-		pwm_backlight_power_on(pb, brightness);
+		pwm_get_state(pb->pwm, &state);
+		state.duty_cycle = duty_cycle;
+		if (!state.enabled)
+			pwm_backlight_power_on(pb, &state);
+		else
+			pwm_apply_state(pb->pwm, &state);
 	} else
 		pwm_backlight_power_off(pb);
 
@@ -447,7 +460,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	struct device_node *node = pdev->dev.of_node;
 	struct pwm_bl_data *pb;
 	struct pwm_state state;
-	struct pwm_args pargs;
 	unsigned int i;
 	int ret;
 
@@ -539,10 +551,26 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 
 	dev_dbg(&pdev->dev, "got pwm for backlight\n");
 
-	if (!data->levels) {
-		/* Get the PWM period (in nanoseconds) */
-		pwm_get_state(pb->pwm, &state);
+	/* Sync up PWM state. */
+	pwm_init_state(pb->pwm, &state);
+
+	/*
+	 * The DT case will set the pwm_period_ns field to 0 and store the
+	 * period, parsed from the DT, in the PWM device. For the non-DT case,
+	 * set the period from platform data if it has not already been set
+	 * via the PWM lookup table.
+	 */
+	if (!state.period && (data->pwm_period_ns > 0))
+		state.period = data->pwm_period_ns;
 
+	ret = pwm_apply_state(pb->pwm, &state);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
+			ret);
+		goto err_alloc;
+	}
+
+	if (!data->levels) {
 		ret = pwm_backlight_brightness_default(&pdev->dev, data,
 						       state.period);
 		if (ret < 0) {
@@ -559,24 +587,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		pb->levels = data->levels;
 	}
 
-	/*
-	 * FIXME: pwm_apply_args() should be removed when switching to
-	 * the atomic PWM API.
-	 */
-	pwm_apply_args(pb->pwm);
-
-	/*
-	 * The DT case will set the pwm_period_ns field to 0 and store the
-	 * period, parsed from the DT, in the PWM device. For the non-DT case,
-	 * set the period from platform data if it has not already been set
-	 * via the PWM lookup table.
-	 */
-	pwm_get_args(pb->pwm, &pargs);
-	pb->period = pargs.period;
-	if (!pb->period && (data->pwm_period_ns > 0))
-		pb->period = data->pwm_period_ns;
-
-	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
+	pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
 
 	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW;
-- 
2.18.0