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

[Kai-Heng Feng]

> On Aug 17, 2020, at 00:22, Runyan, Arthur J <arthur.j.runyan at intel.com> wrote:
> 
> 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. 

Right, I'll wait for a patch then :)

Kai-Heng

> 
> -----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
>> 
>> 
>