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

[Runyan, Arthur J]

You'll need to read out the DDI_BUF_TRANS_* and DISPIO_CR_TX_BMU_CR0 registers at boot before i915 programs them and compare with what driver programs.  
Rodrigo can probably show you how. 

-----Original Message-----
From: Kai-Heng Feng <kai.heng.feng at canonical.com> 
Sent: Thursday, August 13, 2020 10:14 PM
To: Runyan, Arthur J <arthur.j.runyan at intel.com>
Cc: Vivi, Rodrigo <rodrigo.vivi at intel.com>; 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

Hi,

> On Aug 14, 2020, at 01:56, Runyan, Arthur J <arthur.j.runyan at intel.com> wrote:
> 
> 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.

Do you mean to print out value of I915_READ()?
val = I915_READ(CHICKEN_TRANS(transcoder));

Kai-Heng

> 
> -----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
> 
>