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

Wed Aug 26 13:05:11 UTC 2020

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.

> 
> 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