[PATCH] drm/dp_mst: Don't return error code when crtc is null

[Lakha, Bhawanpreet]

[AMD Official Use Only - Internal Distribution Only]


pos->port->connector?
This is checking the crtc not the connector. The crtc can be null if its disabled.

Since it is happening after a unplug->hotplug, I guess we are missing something in the disable sequence and the old connector is still in the list.

Bhawan

>>-----Original Message-----
>>From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf Of
>>Bhawanpreet Lakha
>>Sent: Friday, August 14, 2020 1:02 PM
>>To: mikita.lipski at amd.com; nicholas.kazlauskas at amd.com;
>>alexander.deucher at amd.com
>>Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>; dri-
>>devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org
>>Subject: [PATCH] drm/dp_mst: Don't return error code when crtc is null
>>
>>[Why]
>>In certain cases the crtc can be NULL and returning -EINVAL causes
>>atomic check to fail when it shouln't. This leads to valid
>>configurations failing because atomic check fails.
>
>So is this a bug fix or an exception case, or an expected possibility?
>
>From my reading of the function comments, it is not clear that pos->port->connector
>might be NULL for some reason.

>A better explanation of why this would occur would make this a much more
>useful commit message.
>

>My reading is that you ran into this issue an are masking it with this fix.
>
>Rather than this is a real possibility and this is the correct fix.
>
>Mike
>
>>[How]
>>Don't early return if crtc is null
>>
>>Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
>>---
>> drivers/gpu/drm/drm_dp_mst_topology.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>>diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
>>b/drivers/gpu/drm/drm_dp_mst_topology.c
>>index 70c4b7afed12..bc90a1485699 100644
>>--- a/drivers/gpu/drm/drm_dp_mst_topology.c
>>+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
>>@@ -5037,8 +5037,8 @@ int drm_dp_mst_add_affected_dsc_crtcs(struct
>>drm_atomic_state *state, struct drm
>>
>>                crtc = conn_state->crtc;
>>
>>-              if (WARN_ON(!crtc))
>>-                      return -EINVAL;
>>+              if (!crtc)
>>+                      continue;
>>
>>                if (!drm_dp_mst_dsc_aux_for_port(pos->port))
>>                        continue;
>>--
>>2.17.1
>>
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