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

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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 <lyude@redhat.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Fangzhi Zuo <Jerry.Zuo@amd.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220817193847.557945-9-lyude@redhat.com
This commit is contained in:
Lyude Paul
2022-08-17 15:38:37 -04:00
parent 0b4e477e08
commit a5c2c0d164
5 changed files with 124 additions and 2 deletions
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5
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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@@ -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;