Only synchronize fbdev output to the vblank of an active CRTC. Go over the list of CRTCs and pick the first that matches. Fixes warnings as the one shown below
[ 77.201354] WARNING: drivers/gpu/drm/drm_vblank.c:1320 at drm_crtc_wait_one_vblank+0x194/0x1cc [drm], CPU#1: kworker/1:7/1867 [ 77.201354] omapdrm omapdrm.0: [drm] vblank wait timed out on crtc 0 This currently happens if the fbdev output is not on CRTC 0. Atomic and non-atomic drivers require distinct code paths. As for other fbdev operations, implement both and select the correct one at runtime. Not finding an active CRTC is not a bug. Do not wait in this case, but flush the display update as before. v4: - avoid possible deadlocks with locking context (Sashiko) v3: - drop excessive state validation (Jani) - acquire plane and CRTC mutices (Sashiko) v2: - move look-up code into separate helper - support drivers with legacy modesetting v1: - see https://lore.kernel.org/dri-devel/[email protected]/ Co-authored-by: H. Nikolaus Schaller <[email protected]> Signed-off-by: Thomas Zimmermann <[email protected]> Fixes: d8c4bddcd8bcb ("drm/fb-helper: Synchronize dirty worker with vblank") Tested-by: Icenowy Zheng <[email protected]> Tested-by: H. Nikolaus Schaller <[email protected]> Closes: https://bugs.debian.org/1138033 --- drivers/gpu/drm/drm_fb_helper.c | 92 ++++++++++++++++++++++++++++++++- 1 file changed, 91 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 3316bb00a662..d4664ed468b2 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -225,16 +225,106 @@ static void drm_fb_helper_resume_worker(struct work_struct *work) console_unlock(); } +static int find_crtc_index_atomic(struct drm_fb_helper *helper) +{ + struct drm_device *dev = helper->dev; + int crtc_index = -EINVAL; + struct drm_modeset_acquire_ctx ctx; + struct drm_plane *plane; + int ret = 0; + + drm_modeset_acquire_init(&ctx, 0); + +retry: + drm_for_each_plane(plane, dev) { + const struct drm_plane_state *plane_state; + + if (plane->type != DRM_PLANE_TYPE_PRIMARY) + continue; + + ret = drm_modeset_lock(&plane->mutex, &ctx); + if (ret) + goto err_drm_modeset_lock; + plane_state = plane->state; + + if (plane_state->fb == helper->fb && plane_state->crtc) { + struct drm_crtc *crtc = plane_state->crtc; + + ret = drm_modeset_lock(&crtc->mutex, &ctx); + if (ret) + goto err_drm_modeset_lock; + if (crtc->state->active) + crtc_index = crtc->index; + drm_modeset_unlock(&crtc->mutex); + } + drm_modeset_unlock(&plane->mutex); + + if (crtc_index >= 0) + break; + } + + drm_modeset_drop_locks(&ctx); + drm_modeset_acquire_fini(&ctx); + + return crtc_index; + +err_drm_modeset_lock: + if (ret == -EDEADLK) { + drm_modeset_backoff(&ctx); + goto retry; + } + return ret; +} + +static int find_crtc_index_legacy(struct drm_fb_helper *helper) +{ + struct drm_device *dev = helper->dev; + struct drm_crtc *crtc; + + drm_for_each_crtc(crtc, dev) { + struct drm_plane *plane = crtc->primary; + + if (!crtc->enabled) + continue; + if (!plane || plane->fb != helper->fb) + continue; /* CRTC doesn't display fbdev emulation */ + + return crtc->index; + } + + return -EINVAL; +} + +static int drm_fb_helper_find_crtc_index(struct drm_fb_helper *helper) +{ + struct drm_device *dev = helper->dev; + int crtc_index; + + mutex_lock(&dev->mode_config.mutex); + + if (drm_drv_uses_atomic_modeset(dev)) + crtc_index = find_crtc_index_atomic(helper); + else + crtc_index = find_crtc_index_legacy(helper); + + mutex_unlock(&dev->mode_config.mutex); + + return crtc_index; +} + static void drm_fb_helper_fb_dirty(struct drm_fb_helper *helper) { struct drm_device *dev = helper->dev; struct drm_clip_rect *clip = &helper->damage_clip; struct drm_clip_rect clip_copy; + int crtc_index; unsigned long flags; int ret; mutex_lock(&helper->lock); - drm_client_modeset_wait_for_vblank(&helper->client, 0); + crtc_index = drm_fb_helper_find_crtc_index(helper); + if (crtc_index >= 0) + drm_client_modeset_wait_for_vblank(&helper->client, crtc_index); mutex_unlock(&helper->lock); if (drm_WARN_ON_ONCE(dev, !helper->funcs->fb_dirty)) -- 2.54.0
