[PATCH 0/2] backlight: lp855x: Fixes after c1ff7da03e16

[PATCH 0/2] backlight: lp855x: Fixes after c1ff7da03e16

[Artur Weber]

Two small fixes after commit c1ff7da03e16 ("video: backlight: lp855x:
Get PWM for PWM mode during probe"), stemming from a review[1] by
Uwe Kleine-König.

[1] https://lore.kernel.org/all/20230614083953.e4kkweddjz7wztby@pengutronix.de/

Signed-off-by: Artur Weber <aweber.kernel@gmail.com>

Artur Weber (2):
  backlight: lp855x: Initialize PWM state on first brightness change
  backlight: lp855x: Catch errors when changing brightness

 drivers/video/backlight/lp855x_bl.c | 33 +++++++++++++++++------------
 1 file changed, 20 insertions(+), 13 deletions(-)


base-commit: 7fcd473a6455450428795d20db7afd2691c92336
-- 
2.41.0

[PATCH 1/2] backlight: lp855x: Initialize PWM state on first brightness change

[Artur Weber]

As pointed out by Uwe Kleine-König[1], the changes introduced in
commit c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode
during probe") caused the PWM state set up by the bootloader to be
re-set when the driver is probed. This differs from the behavior from
before that patch, where the PWM state would be initialized on the
first brightness change.

Fix this by moving the PWM state initialization into the PWM control
function. Add a new variable, needs_pwm_init, to the device info struct
to allow us to check whether we need the initialization, or whether it
has already been done.

[1] https://lore.kernel.org/lkml/20230614083953.e4kkweddjz7wztby@pengutronix.de/

Fixes: c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode during probe")
Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
---
 drivers/video/backlight/lp855x_bl.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index 1c9e921bca14..349ec324bc1e 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -71,6 +71,7 @@ struct lp855x {
 	struct device *dev;
 	struct lp855x_platform_data *pdata;
 	struct pwm_device *pwm;
+	bool needs_pwm_init;
 	struct regulator *supply;	/* regulator for VDD input */
 	struct regulator *enable;	/* regulator for EN/VDDIO input */
 };
@@ -220,7 +221,15 @@ static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 {
 	struct pwm_state state;
 
-	pwm_get_state(lp->pwm, &state);
+	if (lp->needs_pwm_init) {
+		pwm_init_state(lp->pwm, &state);
+		/* Legacy platform data compatibility */
+		if (lp->pdata->period_ns > 0)
+			state.period = lp->pdata->period_ns;
+		lp->needs_pwm_init = false;
+	} else {
+		pwm_get_state(lp->pwm, &state);
+	}
 
 	state.duty_cycle = div_u64(br * state.period, max_br);
 	state.enabled = state.duty_cycle;
@@ -387,7 +396,6 @@ static int lp855x_probe(struct i2c_client *cl)
 	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
 	const struct acpi_device_id *acpi_id = NULL;
 	struct device *dev = &cl->dev;
-	struct pwm_state pwmstate;
 	struct lp855x *lp;
 	int ret;
 
@@ -470,15 +478,11 @@ static int lp855x_probe(struct i2c_client *cl)
 		else
 			return dev_err_probe(dev, ret, "getting PWM\n");
 
+		lp->needs_pwm_init = false;
 		lp->mode = REGISTER_BASED;
 		dev_dbg(dev, "mode: register based\n");
 	} else {
-		pwm_init_state(lp->pwm, &pwmstate);
-		/* Legacy platform data compatibility */
-		if (lp->pdata->period_ns > 0)
-			pwmstate.period = lp->pdata->period_ns;
-		pwm_apply_state(lp->pwm, &pwmstate);
-
+		lp->needs_pwm_init = true;
 		lp->mode = PWM_BASED;
 		dev_dbg(dev, "mode: PWM based\n");
 	}
-- 
2.41.0

[PATCH 2/2] backlight: lp855x: Catch errors when changing brightness

[Artur Weber]

The lp855x_bl_update_status function's return type is int, but
it always returns 0, without checking for the results of the
write_byte/pwm_ctrl functions called within.

Make this function return the return values of the functions it
calls, and modify the lp855x_pwm_ctrl function to return errors.

Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
---
 drivers/video/backlight/lp855x_bl.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index 349ec324bc1e..61a7f45bfad8 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -217,7 +217,7 @@ static int lp855x_configure(struct lp855x *lp)
 	return ret;
 }
 
-static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
+static int lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 {
 	struct pwm_state state;
 
@@ -234,23 +234,26 @@ static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 	state.duty_cycle = div_u64(br * state.period, max_br);
 	state.enabled = state.duty_cycle;
 
-	pwm_apply_state(lp->pwm, &state);
+	return pwm_apply_state(lp->pwm, &state);
 }
 
 static int lp855x_bl_update_status(struct backlight_device *bl)
 {
 	struct lp855x *lp = bl_get_data(bl);
 	int brightness = bl->props.brightness;
+	int ret;
 
 	if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
 		brightness = 0;
 
 	if (lp->mode == PWM_BASED)
-		lp855x_pwm_ctrl(lp, brightness, bl->props.max_brightness);
+		ret = lp855x_pwm_ctrl(lp, brightness,
+				      bl->props.max_brightness);
 	else if (lp->mode == REGISTER_BASED)
-		lp855x_write_byte(lp, lp->cfg->reg_brightness, (u8)brightness);
+		ret = lp855x_write_byte(lp, lp->cfg->reg_brightness,
+					(u8)brightness);
 
-	return 0;
+	return ret;
 }
 
 static const struct backlight_ops lp855x_bl_ops = {
-- 
2.41.0

Re: [PATCH 1/2] backlight: lp855x: Initialize PWM state on first brightness change

[Daniel Thompson]

On Fri, Jul 14, 2023 at 02:14:39PM +0200, Artur Weber wrote:
> As pointed out by Uwe Kleine-König[1], the changes introduced in
> commit c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode
> during probe") caused the PWM state set up by the bootloader to be
> re-set when the driver is probed. This differs from the behavior from
> before that patch, where the PWM state would be initialized on the
> first brightness change.
>
> Fix this by moving the PWM state initialization into the PWM control
> function. Add a new variable, needs_pwm_init, to the device info struct
> to allow us to check whether we need the initialization, or whether it
> has already been done.
>
> [1] https://lore.kernel.org/lkml/20230614083953.e4kkweddjz7wztby@pengutronix.de/
>
> Fixes: c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode during probe")
> Signed-off-by: Artur Weber <aweber.kernel@gmail.com>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>

Re: [PATCH 2/2] backlight: lp855x: Catch errors when changing brightness

[Daniel Thompson]

On Fri, Jul 14, 2023 at 02:14:40PM +0200, Artur Weber wrote:
> The lp855x_bl_update_status function's return type is int, but
> it always returns 0, without checking for the results of the
> write_byte/pwm_ctrl functions called within.
>
> Make this function return the return values of the functions it
> calls, and modify the lp855x_pwm_ctrl function to return errors.
>
> Signed-off-by: Artur Weber <aweber.kernel@gmail.com>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>

Re: [PATCH 0/2] backlight: lp855x: Fixes after c1ff7da03e16

[Lee Jones]

On Fri, 14 Jul 2023 14:14:38 +0200, Artur Weber wrote:
> Two small fixes after commit c1ff7da03e16 ("video: backlight: lp855x:
> Get PWM for PWM mode during probe"), stemming from a review[1] by
> Uwe Kleine-König.
> 
> [1] https://lore.kernel.org/all/20230614083953.e4kkweddjz7wztby@pengutronix.de/
> 
> Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
> 
> [...]

Applied, thanks!

[1/2] backlight: lp855x: Initialize PWM state on first brightness change
      commit: 4c09e20b3c85f60353ace21092e34f35f5e3ab00
[2/2] backlight: lp855x: Catch errors when changing brightness
      commit: 5145531be5fbad0e914d1dc1cbd392d7b756abaa

--
Lee Jones [李琼斯]