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Mon, 22 Jun 2026 11:34:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id d3z5FtIdOWrEMgAAD6G6ig (envelope-from ); Mon, 22 Jun 2026 11:34:42 +0000 From: Thomas Zimmermann To: hns@goldelico.com, zhengxingda@iscas.ac.cn, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch, akemnade@kernel.org Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org, kernel@pyra-handheld.com, sashiko-reviews@lists.linux.dev, Thomas Zimmermann , stable@vger.kernel.org Subject: [PATCH v2] drm/fb-helper: Only consider active CRTCs for vblank sync Date: Mon, 22 Jun 2026 13:33:34 +0200 Message-ID: <20260622113434.682292-1-tzimmermann@suse.de> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; FREEMAIL_TO(0.00)[goldelico.com,iscas.ac.cn,linux.intel.com,kernel.org,gmail.com,ffwll.ch]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_TWELVE(0.00)[14]; MIME_TRACE(0.00)[0:+]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[iscas.ac.cn:email,suse.de:email,suse.de:mid,imap1.dmz-prg2.suse.org:helo]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com] X-Spam-Level: X-Spam-Score: -2.80 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. v2: - move look-up code into separate helper - support drivers with legacy modesetting v1: - see https://lore.kernel.org/dri-devel/1c9e0e24-9c4a-4259-8700-cf9e5fd60ca3@suse.de/ Co-authored-by: H. Nikolaus Schaller Signed-off-by: Thomas Zimmermann Fixes: d8c4bddcd8bcb ("drm/fb-helper: Synchronize dirty worker with vblank") Tested-by: Icenowy Zheng Closes: https://bugs.debian.org/1138033 Cc: # v6.19+ --- drivers/gpu/drm/drm_fb_helper.c | 71 ++++++++++++++++++++++++++++++++- 1 file changed, 70 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 7b11a582f8ec..cbf0a9a7b8e5 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -225,16 +225,85 @@ 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; + struct drm_plane *plane; + + drm_for_each_plane(plane, dev) { + const struct drm_plane_state *plane_state; + const struct drm_crtc *crtc; + + if (plane->type != DRM_PLANE_TYPE_PRIMARY) + continue; + + plane_state = plane->state; + if (plane_state->fb != helper->fb || !plane_state->crtc) + continue; /* plane doesn't display fbdev emulation */ + + crtc = plane_state->crtc; + if (!crtc->state->active) + continue; + if (drm_WARN_ON_ONCE(dev, crtc->index > INT_MAX)) + continue; /* driver bug */ + + return crtc->index; + } + + return -EINVAL; +} + +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 */ + if (drm_WARN_ON_ONCE(dev, crtc->index > INT_MAX)) + continue; /* driver bug */ + + 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