linux-kernel - Re: Bogus video resolution in Linux 3.5-rc4

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Date:	Mon, 25 Jun 2012 17:53:12 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Sven Joachim <svenjoac@....de>
Cc:	dri-devel@...ts.freedesktop.org, Adam Jackson <ajax@...hat.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Dave Airlie <airlied@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: Bogus video resolution in Linux 3.5-rc4

At Mon, 25 Jun 2012 16:03:36 +0200,
Sven Joachim wrote:
> 
> After upgrading to Linux 3.5-rc4 from 3.4.4, I noticed that my monitor
> switched to a resolution of 1280x960 rather than the native 1280x1024,
> and nouveau has set up a framebuffer of 1680x945.  It goes without
> saying that the result looks terrible.
> 
> Bisecting shows that the problem started with commit cb21aafe1:
> 
> --8<---------------cut here---------------start------------->8---
> commit cb21aafe121b1c3ad4c77cc5c22320163f16ba42
> Author: Adam Jackson <ajax@...hat.com>
> Date:   Fri Apr 13 16:33:36 2012 -0400
> 
>     drm/edid: Do drm_dmt_modes_for_range() for all range descriptor types
>     
>     EDID 1.4 retcons the meaning of the "GTF feature" bit to mean "is
>     continuous frequency", and moves the set of supported timing formulas
>     into the range descriptor itself.  In any event, the range descriptor
>     can act as a filter on the DMT list without regard to a specific timing
>     formula.
>     
>     Signed-off-by: Adam Jackson <ajax@...hat.com>
>     Tested-by: Takashi Iwai <tiwai@...e.de>
>     Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
>     Signed-off-by: Dave Airlie <airlied@...hat.com>
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index cb40611..9363349 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -1042,12 +1042,13 @@ do_inferred_modes(struct detailed_timing *timing, void *c)
>  {
>  	struct detailed_mode_closure *closure = c;
>  	struct detailed_non_pixel *data = &timing->data.other_data;
> -	int gtf = (closure->edid->features & DRM_EDID_FEATURE_DEFAULT_GTF);
>  
> -	if (gtf && data->type == EDID_DETAIL_MONITOR_RANGE)
> -		closure->modes += drm_dmt_modes_for_range(closure->connector,
> -							  closure->edid,
> -							  timing);
> +	if (data->type != EDID_DETAIL_MONITOR_RANGE)
> +		return;
> +
> +	closure->modes += drm_dmt_modes_for_range(closure->connector,
> +						  closure->edid,
> +						  timing);
>  }
>  
>  static int
> --8<---------------cut here---------------end--------------->8---
> 
> With a kernel from this commit nouveau sets up a resolution of
> 1400x1050; kernels built from commits cffd754 and fc48f16 complain about
> an invalid EDID and use the 1024x768 fallback.
> 
> Attached is the /sys/class/drm/card0-DVI-I-1/edid file from a working
> kernel; in 3.5-rc4 it is identical.

Looking at the EDID data, the problem is likely that your monitor
doesn't give the proper preferred mode.
What does xrandr output show?

And, does the patch below help?


Takashi

---
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 5873e48..dab8580 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -116,6 +116,7 @@ static struct edid_quirk {
 
 	/* Proview AY765C */
 	{ "PTS", 765, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
+	{ "PTS", 793, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
 
 	/* Samsung SyncMaster 205BW.  Note: irony */
 	{ "SAM", 541, EDID_QUIRK_DETAILED_SYNC_PP },
@@ -1404,7 +1405,9 @@ do_detailed_mode(struct detailed_timing *timing, void *c)
 		if (!newmode)
 			return;
 
-		if (closure->preferred)
+		if (closure->preferred ||
+		    ((closure->quirks & EDID_QUIRK_FIRST_DETAILED_PREFERRED) &&
+		     !closure->modes))
 			newmode->type |= DRM_MODE_TYPE_PREFERRED;
 
 		drm_mode_probed_add(closure->connector, newmode);
--
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