[PATCH v2] fbdev: atmel_lcdfb: Rework backlight status updates

[PATCH v2] fbdev: atmel_lcdfb: Rework backlight status updates

[Stephen Kitt]

Instead of checking the state of various backlight_properties fields
against the memorised state in atmel_lcdfb_info.bl_power,
atmel_bl_update_status() should retrieve the desired state using
backlight_get_brightness (which takes into account the power state,
blanking etc.). This means the explicit checks using props.fb_blank
and props.power can be dropped.

The backlight framework ensures that backlight is never negative, so
the test before reading the brightness from the hardware always ends
up false and the whole block can be removed. The framework retrieves
the brightness from the hardware through atmel_bl_get_brightness()
when necessary.

As a result, bl_power in struct atmel_lcdfb_info is no longer
necessary, so remove that while we're at it. Since we only ever care
about reading the current state in backlight_properties, drop the
updates at the end of the function.

Signed-off-by: Stephen Kitt <steve@sk2.org>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-arm-kernel@lists.infradead.org
---
 drivers/video/fbdev/atmel_lcdfb.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/drivers/video/fbdev/atmel_lcdfb.c b/drivers/video/fbdev/atmel_lcdfb.c
index 1fc8de4ecbeb..8187a7c4f910 100644
--- a/drivers/video/fbdev/atmel_lcdfb.c
+++ b/drivers/video/fbdev/atmel_lcdfb.c
@@ -49,7 +49,6 @@ struct atmel_lcdfb_info {
 	struct clk		*lcdc_clk;
 
 	struct backlight_device	*backlight;
-	u8			bl_power;
 	u8			saved_lcdcon;
 
 	u32			pseudo_palette[16];
@@ -109,22 +108,7 @@ static u32 contrast_ctr = ATMEL_LCDC_PS_DIV8
 static int atmel_bl_update_status(struct backlight_device *bl)
 {
 	struct atmel_lcdfb_info *sinfo = bl_get_data(bl);
-	int			power = sinfo->bl_power;
-	int			brightness = bl->props.brightness;
-
-	/* REVISIT there may be a meaningful difference between
-	 * fb_blank and power ... there seem to be some cases
-	 * this doesn't handle correctly.
-	 */
-	if (bl->props.fb_blank != sinfo->bl_power)
-		power = bl->props.fb_blank;
-	else if (bl->props.power != sinfo->bl_power)
-		power = bl->props.power;
-
-	if (brightness < 0 && power == FB_BLANK_UNBLANK)
-		brightness = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL);
-	else if (power != FB_BLANK_UNBLANK)
-		brightness = 0;
+	int			brightness = backlight_get_brightness(bl);
 
 	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, brightness);
 	if (contrast_ctr & ATMEL_LCDC_POL_POSITIVE)
@@ -133,8 +117,6 @@ static int atmel_bl_update_status(struct backlight_device *bl)
 	else
 		lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, contrast_ctr);
 
-	bl->props.fb_blank = bl->props.power = sinfo->bl_power = power;
-
 	return 0;
 }
 
@@ -155,8 +137,6 @@ static void init_backlight(struct atmel_lcdfb_info *sinfo)
 	struct backlight_properties props;
 	struct backlight_device	*bl;
 
-	sinfo->bl_power = FB_BLANK_UNBLANK;
-
 	if (sinfo->backlight)
 		return;
 

base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
-- 
2.30.2

Re: [PATCH v2] fbdev: atmel_lcdfb: Rework backlight status updates

[Sam Ravnborg]

Hi Stephen, thanks!
On Thu, Jun 09, 2022 at 08:04:40PM +0200, Stephen Kitt wrote:
> Instead of checking the state of various backlight_properties fields
> against the memorised state in atmel_lcdfb_info.bl_power,
> atmel_bl_update_status() should retrieve the desired state using
> backlight_get_brightness (which takes into account the power state,
> blanking etc.). This means the explicit checks using props.fb_blank
> and props.power can be dropped.
> 
> The backlight framework ensures that backlight is never negative, so
> the test before reading the brightness from the hardware always ends
> up false and the whole block can be removed. The framework retrieves
> the brightness from the hardware through atmel_bl_get_brightness()
> when necessary.
> 
> As a result, bl_power in struct atmel_lcdfb_info is no longer
> necessary, so remove that while we're at it. Since we only ever care
> about reading the current state in backlight_properties, drop the
> updates at the end of the function.
> 
> Signed-off-by: Stephen Kitt <steve@sk2.org>
> Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Sam Ravnborg <sam@ravnborg.org>

	Sam