[PATCH] drm/panel: s6e63m0: Support max-brightness

[PATCH] drm/panel: s6e63m0: Support max-brightness

[Linus Walleij]

The "max-brightness" is a standard backlight property that
we need to support for the Samsung GT-I8190 Golden because
the display will go black if we crank up the brightness
too high.

As the platform needs this ability to give picture this is
a regression fix along with the addition of the property
to the GT-I8190 device tree.

Cc: Stephan Gerhold <stephan@gerhold.net>
Fixes: 9c3f0a0dd6a1 ("drm/panel: s6e63m0: Implement 28 backlight levels")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpu/drm/panel/panel-samsung-s6e63m0.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
index bf6d704d4d27..603c5dfe8768 100644
--- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
+++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
@@ -692,12 +692,12 @@ static const struct backlight_ops s6e63m0_backlight_ops = {
 	.update_status	= s6e63m0_set_brightness,
 };
 
-static int s6e63m0_backlight_register(struct s6e63m0 *ctx)
+static int s6e63m0_backlight_register(struct s6e63m0 *ctx, u32 max_brightness)
 {
 	struct backlight_properties props = {
 		.type		= BACKLIGHT_RAW,
-		.brightness	= MAX_BRIGHTNESS,
-		.max_brightness = MAX_BRIGHTNESS
+		.brightness	= max_brightness,
+		.max_brightness = max_brightness,
 	};
 	struct device *dev = ctx->dev;
 	int ret = 0;
@@ -719,6 +719,7 @@ int s6e63m0_probe(struct device *dev,
 		  bool dsi_mode)
 {
 	struct s6e63m0 *ctx;
+	u32 max_brightness;
 	int ret;
 
 	ctx = devm_kzalloc(dev, sizeof(struct s6e63m0), GFP_KERNEL);
@@ -734,6 +735,14 @@ int s6e63m0_probe(struct device *dev,
 	ctx->enabled = false;
 	ctx->prepared = false;
 
+	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
+	if (ret)
+		max_brightness = MAX_BRIGHTNESS;
+	if (max_brightness > MAX_BRIGHTNESS) {
+		dev_err(dev, "illegal max brightness specified\n");
+		max_brightness = MAX_BRIGHTNESS;
+	}
+
 	ctx->supplies[0].supply = "vdd3";
 	ctx->supplies[1].supply = "vci";
 	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
@@ -753,7 +762,7 @@ int s6e63m0_probe(struct device *dev,
 		       dsi_mode ? DRM_MODE_CONNECTOR_DSI :
 		       DRM_MODE_CONNECTOR_DPI);
 
-	ret = s6e63m0_backlight_register(ctx);
+	ret = s6e63m0_backlight_register(ctx, max_brightness);
 	if (ret < 0)
 		return ret;
 
-- 
2.29.2

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Re: [PATCH] drm/panel: s6e63m0: Support max-brightness

[Sam Ravnborg]

Hi Linus.
On Mon, Dec 14, 2020 at 11:22:10PM +0100, Linus Walleij wrote:
> The "max-brightness" is a standard backlight property that
> we need to support for the Samsung GT-I8190 Golden because
> the display will go black if we crank up the brightness
> too high.
> 
> As the platform needs this ability to give picture this is
> a regression fix along with the addition of the property
> to the GT-I8190 device tree.
> 
> Cc: Stephan Gerhold <stephan@gerhold.net>
> Fixes: 9c3f0a0dd6a1 ("drm/panel: s6e63m0: Implement 28 backlight levels")
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Looks good. backlight_properties.max_brightness is an int, but this
looks like a sub-optimal type so the use of u32 in this patch is fine.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>

As we are in the merge window it should be drm-next-fixes material,
but you may have to wait until -rc2 before the drm-next-fixes branched
is ready.

	Sam

> ---
>  drivers/gpu/drm/panel/panel-samsung-s6e63m0.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
> index bf6d704d4d27..603c5dfe8768 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
> @@ -692,12 +692,12 @@ static const struct backlight_ops s6e63m0_backlight_ops = {
>  	.update_status	= s6e63m0_set_brightness,
>  };
>  
> -static int s6e63m0_backlight_register(struct s6e63m0 *ctx)
> +static int s6e63m0_backlight_register(struct s6e63m0 *ctx, u32 max_brightness)
>  {
>  	struct backlight_properties props = {
>  		.type		= BACKLIGHT_RAW,
> -		.brightness	= MAX_BRIGHTNESS,
> -		.max_brightness = MAX_BRIGHTNESS
> +		.brightness	= max_brightness,
> +		.max_brightness = max_brightness,
>  	};
>  	struct device *dev = ctx->dev;
>  	int ret = 0;
> @@ -719,6 +719,7 @@ int s6e63m0_probe(struct device *dev,
>  		  bool dsi_mode)
>  {
>  	struct s6e63m0 *ctx;
> +	u32 max_brightness;
>  	int ret;
>  
>  	ctx = devm_kzalloc(dev, sizeof(struct s6e63m0), GFP_KERNEL);
> @@ -734,6 +735,14 @@ int s6e63m0_probe(struct device *dev,
>  	ctx->enabled = false;
>  	ctx->prepared = false;
>  
> +	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
> +	if (ret)
> +		max_brightness = MAX_BRIGHTNESS;
> +	if (max_brightness > MAX_BRIGHTNESS) {
> +		dev_err(dev, "illegal max brightness specified\n");
> +		max_brightness = MAX_BRIGHTNESS;
> +	}
> +
>  	ctx->supplies[0].supply = "vdd3";
>  	ctx->supplies[1].supply = "vci";
>  	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
> @@ -753,7 +762,7 @@ int s6e63m0_probe(struct device *dev,
>  		       dsi_mode ? DRM_MODE_CONNECTOR_DSI :
>  		       DRM_MODE_CONNECTOR_DPI);
>  
> -	ret = s6e63m0_backlight_register(ctx);
> +	ret = s6e63m0_backlight_register(ctx, max_brightness);
>  	if (ret < 0)
>  		return ret;
>  
> -- 
> 2.29.2
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