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.
-----Original Message----- From: Kai-Heng Feng <[email protected]> Sent: Thursday, August 13, 2020 10:14 PM To: Runyan, Arthur J <[email protected]> Cc: Vivi, Rodrigo <[email protected]>; Ville Syrjälä <[email protected]>; intel-gfx <[email protected]> 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 <[email protected]> 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 <[email protected]> > Sent: Thursday, August 13, 2020 9:50 AM > To: Kai-Heng Feng <[email protected]>; Runyan, Arthur J > <[email protected]> > Cc: Ville Syrjälä <[email protected]>; intel-gfx > <[email protected]> > 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 <[email protected]> >> 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 <[email protected]> >> 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 <[email protected]> >> Cc: Art Runyan <[email protected]> >> Signed-off-by: Ville Syrjälä <[email protected]> >> Link: >> https://patchwork.freedesktop.org/patch/msgid/[email protected] >> Reviewed-by: Rodrigo Vivi <[email protected]> >> >> >> dmesg from drm-tip with drm.debug=0xe can be found here: >> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1871721/comments >> / >> 64 >> >> Kai-Heng > > _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
