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

Kai-Heng Feng kai.heng.feng at canonical.com
Thu Sep 3 06:26:16 UTC 2020 


> On Aug 26, 2020, at 21:05, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> 
> On Wed, Aug 26, 2020 at 12:40:15PM +0800, Kai-Heng Feng wrote:
>> 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
> 
> Looks like it's using the 400mV/0dB setting. Can we get the same dumps
> with the driver loaded just to confirm whether we're using different
> settings? 
> 
> Also a dump of /sys/kernel/debug/dri/0/i915_vbt would be good
> to have.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/124
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/125
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments/126

Kai-Heng

> 
>> 
>> 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
> 
> -- 
> Ville Syrjälä
> Intel

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