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* [PATCH] video: backlight: Drop maximum brightness override for brightness zero
@ 2021-07-09 13:26 Marek Vasut
  2021-07-09 13:53 ` Noralf Trønnes
  0 siblings, 1 reply; 3+ messages in thread
From: Marek Vasut @ 2021-07-09 13:26 UTC (permalink / raw)
  To: dri-devel
  Cc: linux-fbdev, Marek Vasut, Daniel Thompson, Meghana Madhyastha,
	Noralf Trønnes, Sean Paul, Thierry Reding

The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
in backlight.c") says that gpio-backlight uses brightness as power state.
This has been fixed since in ec665b756e6f7 ("backlight: gpio-backlight:
Correct initial power state handling") and other backlight drivers do not
require this workaround. Drop the workaround.

This fixes the case where e.g. pwm-backlight can perfectly well be set to
brightness 0 on boot in DT, which without this patch leads to the display
brightness to be max instead of off.

Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Thierry Reding <treding@nvidia.com>
---
 drivers/video/backlight/backlight.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 537fe1b376ad7..fc990e576340b 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -688,12 +688,6 @@ static struct backlight_device *of_find_backlight(struct device *dev)
 			of_node_put(np);
 			if (!bd)
 				return ERR_PTR(-EPROBE_DEFER);
-			/*
-			 * Note: gpio_backlight uses brightness as
-			 * power state during probe
-			 */
-			if (!bd->props.brightness)
-				bd->props.brightness = bd->props.max_brightness;
 		}
 	}
 
-- 
2.30.2


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] video: backlight: Drop maximum brightness override for brightness zero
  2021-07-09 13:26 [PATCH] video: backlight: Drop maximum brightness override for brightness zero Marek Vasut
@ 2021-07-09 13:53 ` Noralf Trønnes
  2021-07-12 10:25   ` Daniel Thompson
  0 siblings, 1 reply; 3+ messages in thread
From: Noralf Trønnes @ 2021-07-09 13:53 UTC (permalink / raw)
  To: Marek Vasut, dri-devel
  Cc: linux-fbdev, Daniel Thompson, Meghana Madhyastha, Sean Paul,
	Thierry Reding



Den 09.07.2021 15.26, skrev Marek Vasut:
> The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
> in backlight.c") says that gpio-backlight uses brightness as power state.
> This has been fixed since in ec665b756e6f7 ("backlight: gpio-backlight:
> Correct initial power state handling") and other backlight drivers do not
> require this workaround. Drop the workaround.
> 
> This fixes the case where e.g. pwm-backlight can perfectly well be set to
> brightness 0 on boot in DT, which without this patch leads to the display
> brightness to be max instead of off.
> 
> Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")

I not sure about the rules, but if this is automatically picked up for
stable, maybe this is needed to avoid changing behaviour on 4.19:

Cc: <stable@vger.kernel.org> # 5.4+

of_find_backlight() was added in 4.17 and the gpio fix in 5.4.

Or perhaps there are other ways to signal this dependency.

> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Daniel Thompson <daniel.thompson@linaro.org>
> Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> Cc: Noralf Trønnes <noralf@tronnes.org>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Thierry Reding <treding@nvidia.com>
> ---

Acked-by: Noralf Trønnes <noralf@tronnes.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] video: backlight: Drop maximum brightness override for brightness zero
  2021-07-09 13:53 ` Noralf Trønnes
@ 2021-07-12 10:25   ` Daniel Thompson
  0 siblings, 0 replies; 3+ messages in thread
From: Daniel Thompson @ 2021-07-12 10:25 UTC (permalink / raw)
  To: Noralf Trønnes
  Cc: Marek Vasut, dri-devel, linux-fbdev, Meghana Madhyastha,
	Sean Paul, Thierry Reding

On Fri, Jul 09, 2021 at 03:53:16PM +0200, Noralf Trønnes wrote:
> 
> 
> Den 09.07.2021 15.26, skrev Marek Vasut:
> > The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
> > in backlight.c") says that gpio-backlight uses brightness as power state.
> > This has been fixed since in ec665b756e6f7 ("backlight: gpio-backlight:
> > Correct initial power state handling") and other backlight drivers do not
> > require this workaround. Drop the workaround.
> > 
> > This fixes the case where e.g. pwm-backlight can perfectly well be set to
> > brightness 0 on boot in DT, which without this patch leads to the display
> > brightness to be max instead of off.
> > 
> > Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")
> 
> I not sure about the rules, but if this is automatically picked up for
> stable, maybe this is needed to avoid changing behaviour on 4.19:
> 
> 
> of_find_backlight() was added in 4.17 and the gpio fix in 5.4.
> 
> Or perhaps there are other ways to signal this dependency.

Agree we need to make sure the Fixes: tag doesn't provoke regressions
in v4.19.

Is this the syntax appropriate?

Cc: <stable@vger.kernel.org> # 5.4+
Cc: <stable@vger.kernel.org> # 4.19.x: ec665b756e6f7: backlight: gpio-backlight: Correct initial power state handling


> > Signed-off-by: Marek Vasut <marex@denx.de>
> > Cc: Daniel Thompson <daniel.thompson@linaro.org>
> > Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> > Cc: Noralf Trønnes <noralf@tronnes.org>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Cc: Thierry Reding <treding@nvidia.com>
> > ---
> 
> Acked-by: Noralf Trønnes <noralf@tronnes.org>

With the above (or something similar to avoid problems with v4.19):
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-07-12 10:26 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-07-09 13:26 [PATCH] video: backlight: Drop maximum brightness override for brightness zero Marek Vasut
2021-07-09 13:53 ` Noralf Trønnes
2021-07-12 10:25   ` Daniel Thompson

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