[Intel-gfx] [Regression] "drm/i915: Implement display w/a #1143" breaks HDMI on ASUS GL552VW

[Runyan, Arthur J]

The workaround is freeing up stuck vswing values to let new vswing programming kick in.  Maybe the new vswing values are wrong.
Try checking the vswing that driver programs against what BIOS/GOP programs.

-----Original Message-----
From: Vivi, Rodrigo <rodrigo.vivi at intel.com> 
Sent: Thursday, August 13, 2020 9:50 AM
To: Kai-Heng Feng <kai.heng.feng at canonical.com>; Runyan, Arthur J <arthur.j.runyan at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>; intel-gfx <intel-gfx at lists.freedesktop.org>
Subject: Re: [Regression] "drm/i915: Implement display w/a #1143" breaks HDMI on ASUS GL552VW

Art, any comment here?

I just checked and the  W/a 1143 is implemented as described, but it is failing HDMI on this hybrid system.

> On Aug 12, 2020, at 9:07 PM, Kai-Heng Feng <kai.heng.feng at canonical.com> wrote:
> 
> Hi,
> 
> There's a regression reported that HDMI output stops working after os upgrade:
> https://bugs.launchpad.net/bugs/1871721
> 
> Here's the bisect result:
> 0519c102f5285476d7868a387bdb6c58385e4074 is the first bad commit 
> commit 0519c102f5285476d7868a387bdb6c58385e4074
> Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Date:   Mon Jan 22 19:41:31 2018 +0200
> 
>    drm/i915: Implement display w/a #1143
> 
>    Apparently SKL/KBL/CFL need some manual help to get the
>    programmed HDMI vswing to stick. Implement the relevant
>    workaround (display w/a #1143).
> 
>    Note that the relevant chicken bits live in a transcoder register
>    even though the bits affect a specific DDI port rather than a
>    specific transcoder. Hence we must pick the correct transcoder
>    register instance based on the port rather than based on the
>    cpu_transcoder.
> 
>    Also note that for completeness I included support for DDI A/E
>    in the code even though we never have HDMI on those ports.
> 
>    v2: CFL needs the w/a as well (Rodrigo and Art)
> 
>    Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>    Cc: Art Runyan <arthur.j.runyan at intel.com>
>    Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>    Link: https://patchwork.freedesktop.org/patch/msgid/20180122174131.28046-1-ville.syrjala@linux.intel.com
>    Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> 
> 
> dmesg from drm-tip with drm.debug=0xe can be found here:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/
> 64
> 
> Kai-Heng