linux-kernel - Re: [PATCH v2] drm: use mgr->dev in drm_dbg_kms in drm_dp_add_payload

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Message-ID: <Zi7PgLmTp5lJWS91@debian.local>
Date: Sun, 28 Apr 2024 23:36:48 +0100
From: Chris Bainbridge <chris.bainbridge@...il.com>
To: Lyude Paul <lyude@...hat.com>
Cc: Jeff Layton <jlayton@...nel.org>, David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>, Wayne.Lin@....com,
	alexdeucher@...il.com, Jani Nikula <jani.nikula@...ux.intel.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm: use mgr->dev in drm_dbg_kms in
 drm_dp_add_payload_part2

On Tue, Jun 20, 2023 at 03:59:24PM -0400, Lyude Paul wrote:
> Also since I forgot, so patchwork picks this up:
> 
> Reviewed-by: Lyude Paul <lyude@...hat.com>
> 
> On Tue, 2023-06-20 at 15:50 -0400, Lyude Paul wrote:
> > Eek - this might have been a situation where everyone involved assumed someone
> > else would push it, whoops. I'll make sure this is pushed upstream :).
> > 
> > FWIW: You could definitely send an MR to the fedora kernel's gitlab to get
> > this included earlier. If you don't get to it before me I'll try to do that
> > today
> > 
> > On Tue, 2023-06-20 at 07:18 -0400, Jeff Layton wrote:
> > > I've noticed that this patch is not included in linux-next currently.
> > > 
> > > Can I get some confirmation that this is going to be included in v6.5?
> > > Currently, I've been having to rebuild Fedora kernels to avoid this
> > > panic, and I'd like to know there is a light at the end of that tunnel.
> > > 
> > > Thanks,
> > > Jeff
> > > 
> > > On Wed, 2023-04-19 at 16:54 -0400, Lyude Paul wrote:
> > > > Reviewed-by: Lyude Paul <lyude@...hat.com>
> > > > 
> > > > Thanks!
> > > > 
> > > > On Wed, 2023-04-19 at 07:24 -0400, Jeff Layton wrote:
> > > > > I've been experiencing some intermittent crashes down in the display
> > > > > driver code. The symptoms are ususally a line like this in dmesg:
> > > > > 
> > > > >     amdgpu 0000:30:00.0: [drm] Failed to create MST payload for port 000000006d3a3885: -5
> > > > > 
> > > > > ...followed by an Oops due to a NULL pointer dereference.
> > > > > 
> > > > > Switch to using mgr->dev instead of state->dev since "state" can be
> > > > > NULL in some cases.
> > > > > 
> > > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2184855
> > > > > Suggested-by: Jani Nikula <jani.nikula@...ux.intel.com>
> > > > > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > > > > ---
> > > > >  drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > 
> > > > > I've been running this patch for a couple of days, but the problem
> > > > > hasn't occurred again as of yet. It seems sane though as long as we can
> > > > > assume that mgr->dev will be valid even when "state" is a NULL pointer.
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > index 38dab76ae69e..e2e21ce79510 100644
> > > > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > @@ -3404,7 +3404,7 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
> > > > >  
> > > > >  	/* Skip failed payloads */
> > > > >  	if (payload->vc_start_slot == -1) {
> > > > > -		drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
> > > > > +		drm_dbg_kms(mgr->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
> > > > >  			    payload->port->connector->name);
> > > > >  		return -EIO;
> > > > >  	}
> > > > 
> > > 
> > 
> 
> -- 
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
> 

Hello, this patch regressed in Wayne's 5aa1dfcdf0a42 commit:

$ git show 5aa1dfcdf0a42 | grep -A6 'Skip failed payloads'
 	/* Skip failed payloads */
-	if (payload->vc_start_slot == -1) {
-		drm_dbg_kms(mgr->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
+	if (payload->payload_allocation_status != DRM_DP_MST_PAYLOAD_ALLOCATION_DFP) {
+		drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
 			    payload->port->connector->name);
 		return -EIO;

$ git tag --contains 5aa1dfcdf0a42
v6.7
v6.7-rc1
v6.7-rc2
v6.7-rc3
v6.7-rc4
v6.7-rc5
v6.7-rc6
v6.7-rc7
v6.7-rc8
v6.7.1
v6.7.10
v6.7.11
v6.7.12
v6.7.2
v6.7.3
v6.7.4
v6.7.5
v6.7.6
v6.7.7
v6.7.8
v6.7.9
v6.8
v6.8-rc1
v6.8-rc2
v6.8-rc3
v6.8-rc4
v6.8-rc5
v6.8-rc6
v6.8-rc7
v6.8.1
v6.8.2
v6.8.3
v6.8.4
v6.8.5
v6.8.6
v6.8.7
v6.8.8
v6.9-rc1
v6.9-rc2
v6.9-rc3
v6.9-rc4
v6.9-rc5