On 2021-09-07 10:10 a.m., Nicholas Kazlauskas wrote:
> [Why]
> If we're running a headless config with 0 links then the vblank
> workqueue will be NULL - causing a NULL pointer exception during
> any commit.
>
> [How]
> Guard access to the workqueue if it's NULL and don't queue or flush
> work if it is.
>
> Cc: Roman Li <roman...@amd.com>
> Cc: Wayne Lin <wayne....@amd.com>
> Cc: Harry Wentland <harry.wentl...@amd.com>
> Reported-by: Mike Lothian <m...@fireburn.co.uk>
> BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1700
> Fixes: 91f86d4cce2 ("drm/amd/display: Use vblank control events for PSR
> enable/disable")
> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlaus...@amd.com>
Reviewed-by: Harry Wentland <harry.wentl...@amd.com>
Harry
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 32 +++++++++++--------
> 1 file changed, 18 insertions(+), 14 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 8837259215d..46e08736f94 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6185,21 +6185,23 @@ static inline int dm_set_vblank(struct drm_crtc
> *crtc, bool enable)
> return 0;
>
> #if defined(CONFIG_DRM_AMD_DC_DCN)
> - work = kzalloc(sizeof(*work), GFP_ATOMIC);
> - if (!work)
> - return -ENOMEM;
> + if (dm->vblank_control_workqueue) {
> + work = kzalloc(sizeof(*work), GFP_ATOMIC);
> + if (!work)
> + return -ENOMEM;
>
> - INIT_WORK(&work->work, vblank_control_worker);
> - work->dm = dm;
> - work->acrtc = acrtc;
> - work->enable = enable;
> + INIT_WORK(&work->work, vblank_control_worker);
> + work->dm = dm;
> + work->acrtc = acrtc;
> + work->enable = enable;
>
> - if (acrtc_state->stream) {
> - dc_stream_retain(acrtc_state->stream);
> - work->stream = acrtc_state->stream;
> - }
> + if (acrtc_state->stream) {
> + dc_stream_retain(acrtc_state->stream);
> + work->stream = acrtc_state->stream;
> + }
>
> - queue_work(dm->vblank_control_workqueue, &work->work);
> + queue_work(dm->vblank_control_workqueue, &work->work);
> + }
> #endif
>
> return 0;
> @@ -8809,7 +8811,8 @@ static void amdgpu_dm_commit_planes(struct
> drm_atomic_state *state,
> * If PSR or idle optimizations are enabled then flush out
> * any pending work before hardware programming.
> */
> - flush_workqueue(dm->vblank_control_workqueue);
> + if (dm->vblank_control_workqueue)
> + flush_workqueue(dm->vblank_control_workqueue);
> #endif
>
> bundle->stream_update.stream = acrtc_state->stream;
> @@ -9144,7 +9147,8 @@ static void amdgpu_dm_atomic_commit_tail(struct
> drm_atomic_state *state)
> /* if there mode set or reset, disable eDP PSR */
> if (mode_set_reset_required) {
> #if defined(CONFIG_DRM_AMD_DC_DCN)
> - flush_workqueue(dm->vblank_control_workqueue);
> + if (dm->vblank_control_workqueue)
> + flush_workqueue(dm->vblank_control_workqueue);
> #endif
> amdgpu_dm_psr_disable_all(dm);
> }
>
