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

Tue Oct 13 11:15:32 UTC 2020

On Tue, Oct 13, 2020 at 01:20:35PM +0800, Kai-Heng Feng wrote:
> 
> 
> > On Sep 3, 2020, at 14:26, Kai-Heng Feng <kai.heng.feng at canonical.com> wrote:
> > 
> > 
> > 
> >> 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
> 
> A gentle ping...

I cooked up some hacks for you to try:
git://github.com/vsyrjala/linux.git skl_vswing_wa_hacks

An upstream bug report would probably be a good idea so that the
communication doesn't have to go through a middle man over email...

> 
> > 
> > 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
> > 

-- 
Ville Syrjälä
Intel