[PATCH] drm/i915: Fix inconsistent backlight level during disabled

[PATCH] drm/i915: Fix inconsistent backlight level during disabled

[Takashi Iwai]

When the brightness property is inquired while the backlight is disabled,
the driver returns a wrong value (zero) because it probes the value after
the backlight was turned off.  This caused a black screen even after the
backlight is enabled again.  It should return the internal backlight_level
instead, so that it won't be influenced by the backlight-enable state.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=41926
BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/872652

Tested-by: Kamal Mostafa <kamal@canonical.com>
Cc: Alex Davis <alex14641@yahoo.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/gpu/drm/i915/intel_panel.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 499d4c0..21f60b7 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -326,7 +326,8 @@ static int intel_panel_update_status(struct backlight_device *bd)
 static int intel_panel_get_brightness(struct backlight_device *bd)
 {
 	struct drm_device *dev = bl_get_data(bd);
-	return intel_panel_get_backlight(dev);
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	return dev_priv->backlight_level;
 }
 
 static const struct backlight_ops intel_panel_bl_ops = {
-- 
1.7.7

Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

[Alex Davis]

>diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
>index 499d4c0..21f60b7 100644
>--- a/drivers/gpu/drm/i915/intel_panel.c
>+++ b/drivers/gpu/drm/i915/intel_panel.c
>@@ -326,7 +326,8 @@ static int intel_panel_update_status(struct backlight_device *bd)
>static int intel_panel_get_brightness(struct backlight_device *bd)
>{
>    struct drm_device *dev = bl_get_data(bd);
>-    return intel_panel_get_backlight(dev);
>+    struct drm_i915_private *dev_priv = dev->dev_private;
>+    return dev_priv->backlight_level;
>}
>
>static const struct backlight_ops intel_panel_bl_ops = {
>-- 
>1.7.7

I'll test this patch sometime this weekend.

Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

[Keith Packard]

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On Wed, 16 Nov 2011 10:58:03 +0100, Takashi Iwai <tiwai@suse.de> wrote:

> When the brightness property is inquired while the backlight is disabled,
> the driver returns a wrong value (zero) because it probes the value after
> the backlight was turned off.  This caused a black screen even after the
> backlight is enabled again.  It should return the internal backlight_level
> instead, so that it won't be influenced by the backlight-enable state.

Yes, this looks correct by inspection to me. I'll stick it into
drm-intel-fixes.

-- 
keith.packard@intel.com

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Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

[Woody Suwalski]

Takashi Iwai wrote:
> When the brightness property is inquired while the backlight is disabled,
> the driver returns a wrong value (zero) because it probes the value after
> the backlight was turned off.  This caused a black screen even after the
> backlight is enabled again.  It should return the internal backlight_level
> instead, so that it won't be influenced by the backlight-enable state.
>
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=41926
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/872652
>
> Tested-by: Kamal Mostafa<kamal@canonical.com>
> Cc: Alex Davis<alex14641@yahoo.com>
> Cc:<stable@kernel.org>
> Signed-off-by: Takashi Iwai<tiwai@suse.de>
> ---
>   drivers/gpu/drm/i915/intel_panel.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 499d4c0..21f60b7 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -326,7 +326,8 @@ static int intel_panel_update_status(struct backlight_device *bd)
>   static int intel_panel_get_brightness(struct backlight_device *bd)
>   {
>   	struct drm_device *dev = bl_get_data(bd);
> -	return intel_panel_get_backlight(dev);
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	return dev_priv->backlight_level;
>   }
>
>   static const struct backlight_ops intel_panel_bl_ops = {
Seems to be fixing a black-screen regression since 3.0 on EeePC devices 
as well...

Thanks, Woody

Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

[Alex Davis]

>>diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
>>index 499d4c0..21f60b7 100644
>>--- a/drivers/gpu/drm/i915/intel_panel.c
>>+++ b/drivers/gpu/drm/i915/intel_panel.c
>>@@ -326,7 +326,8 @@ static int intel_panel_update_status(struct backlight_device *bd)
>>static int intel_panel_get_brightness(struct backlight_device *bd)
>>{
>>    struct drm_device *dev = bl_get_data(bd);
>>-    return intel_panel_get_backlight(dev);
>>+    struct drm_i915_private *dev_priv = dev->dev_private;
>>+    return dev_priv->backlight_level;
>>}
>>
>>static const struct backlight_ops intel_panel_bl_ops = {
>>-- 
>>1.7.7
>
>I'll test this patch sometime this weekend.

This patch works for me.

Tested-by: Alex Davis<alex14641@yahoo.com>