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

Wed Aug 26 04:40:15 UTC 2020

Hi,

> On Aug 25, 2020, at 02:46, Runyan, Arthur J <arthur.j.runyan at intel.com> wrote:
> 
> I remember some strangeness about the blnclegdisbl.  I'll see if I can dig up some more.

The register read can be found at [1] and [2].

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/119
[2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/120

Kai-Heng

> 
> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com> 
> Sent: Monday, August 24, 2020 11:05 AM
> To: Kai-Heng Feng <kai.heng.feng at canonical.com>
> Cc: Runyan, Arthur J <arthur.j.runyan at intel.com>; Vivi, Rodrigo <rodrigo.vivi at 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
> 
> On Mon, Aug 17, 2020 at 02:17:49PM +0800, Kai-Heng Feng wrote:
>> 
>> 
>>> 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 :)
> 
> To grab the BIOS reg values we just have to make sure the driver doesn't load. Eg. pass something like "modprobe.blacklist=i915,snd_hda_intel 3" to the kernel cmdline (+ whatever other magic ubuntu might require). Confirm with something like "lsmod | grep i915" to make sure the driver didn't sneak in despite our best efforts.
> 
> Then we can dump the registers with intel_reg from igt-gpu-tools:
> intel_reg read --count 20 0x64E00 0x64E60 0x64EC0 0x64F20 0x64F80 intel_reg read 0x64000 0x64100 0x64200 0x64300 0x64400 0x6C00C
> 
> The only somewhat suspicious thing I noticed is that we treat DISPIO_CR_TX_BMU_CR0:tx_blnclegdisbl as a bitmask (bit 23 -> DDI A, bit 24 -> DDI B, etc.) whereas the spec seems to be saying that we should just zero out all the bits of tx_blnclegdisbl when any DDI needs iboost. Art, is our interpretation of the bits correct or just a fairy tale?
> 
>> 
>> 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 at 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/comme
>>>>> nts
>>>>> /
>>>>> 64
>>>>> 
>>>>> Kai-Heng
>>>> 
>>>> 
>>> 
> 
> --
> Ville Syrjälä
> Intel