drm/display/dp_mst: Add nonblocking helpers for DP MST

As Daniel Vetter pointed out, if we only use the atomic modesetting locks
with MST it's technically possible for a driver with non-blocking modesets
to race when it comes to MST displays - as we make the mistake of not doing
our own CRTC commit tracking in the topology_state object.

This could potentially cause problems if something like this happens:

* User starts non-blocking commit to disable CRTC-1 on MST topology 1
* User starts non-blocking commit to enable CRTC-2 on MST topology 1

There's no guarantee here that the commit for disabling CRTC-2 will only
occur after CRTC-1 has finished, since neither commit shares a CRTC - only
the private modesetting object for MST. Keep in mind this likely isn't a
problem for blocking modesets, only non-blocking.

So, begin fixing this by keeping track of which CRTCs on a topology have
changed by keeping track of which CRTCs we release or allocate timeslots
on. As well, add some helpers for:

* Setting up the drm_crtc_commit structs in the ->commit_setup hook
* Waiting for any CRTC dependencies from the previous topology state

v2:
* Use drm_dp_mst_atomic_setup_commit() directly - Jani

Signed-off-by: Lyude Paul <[email protected]>
Cc: Wayne Lin <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Fangzhi Zuo <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Sean Paul <[email protected]>
Acked-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index cd30b02af8ee..c97a4d759b94 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2808,7 +2808,8 @@ static const struct drm_mode_config_funcs amdgpu_dm_mode_funcs = {
 };
 
 static struct drm_mode_config_helper_funcs amdgpu_dm_mode_config_helperfuncs = {
-	.atomic_commit_tail = amdgpu_dm_atomic_commit_tail
+	.atomic_commit_tail = amdgpu_dm_atomic_commit_tail,
+	.atomic_commit_setup = drm_dp_mst_atomic_setup_commit,
 };
 
 static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
@@ -7959,6 +7960,7 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		DRM_ERROR("Waiting for fences timed out!");
 
 	drm_atomic_helper_update_legacy_modeset_state(dev, state);
+	drm_dp_mst_atomic_wait_for_dependencies(state);
 
 	dm_state = dm_atomic_get_new_state(state);
 	if (dm_state && dm_state->context) {
@@ -8357,7 +8359,6 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		dc_release_state(dc_state_temp);
 }
 
-
 static int dm_force_atomic_commit(struct drm_connector *connector)
 {
 	int ret = 0;