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

Rodrigo Vivi rodrigo.vivi at intel.com
Wed Apr 7 14:34:02 UTC 2021 

On Tue, Oct 13, 2020 at 02:15:32PM +0300, Ville Syrjälä wrote:
> 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...

any update on this?
Cc: Jani

> 
> > 
> > > 
> > > 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

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