From 51f644b40b4b794b28b982fdd5d0dd8ee63f9272 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Fri, 12 Jun 2020 18:00:49 +0200 Subject: drm/atomic-helper: reset vblank on crtc reset Only when vblanks are supported ofc. Some drivers do this already, but most unfortunately missed it. This opens up bugs after driver load, before the crtc is enabled for the first time. syzbot spotted this when loading vkms as a secondary output. Given how many drivers are buggy it's best to solve this once and for all in shared helper code. Aside from moving the few existing calls to drm_crtc_vblank_reset into helpers (i915 doesn't use helpers, so keeps its own) I think the regression risk is minimal: atomic helpers already rely on drivers calling drm_crtc_vblank_on/off correctly in their hooks when they support vblanks. And driver that's failing to handle vblanks after this is missing those calls already, and vblanks could only work by accident when enabling a CRTC for the first time right after boot. Big thanks to Tetsuo for helping track down what's going wrong here. There's only a few drivers which already had the necessary call and needed some updating: - komeda, atmel and tidss also needed to be changed to call __drm_atomic_helper_crtc_reset() intead of open coding it - tegra and msm even had it in the same place already, just code motion, and malidp already uses __drm_atomic_helper_crtc_reset(). - Laurent noticed that rcar-du and omap open-code their crtc reset and hence would actually be broken by this patch now. So fix them up by reusing the helpers, which brings the drm_crtc_vblank_reset() back. Only call left is in i915, which doesn't use drm_mode_config_reset, but has its own fastboot infrastructure. So that's the only case where we actually want this in the driver still. I've also reviewed all other drivers which set up vblank support with drm_vblank_init. After the previous patch fixing mxsfb all atomic drivers do call drm_crtc_vblank_on/off as they should, the remaining drivers are either legacy kms or legacy dri1 drivers, so not affected by this change to atomic helpers. v2: Use the drm_dev_has_vblank() helper. v3: Laurent pointed out that omap and rcar-du used drm_crtc_vblank_off instead of drm_crtc_vblank_reset. Adjust them too. v4: Laurent noticed that rcar-du and omap open-code their crtc reset and hence would actually be broken by this patch now. So fix them up by reusing the helpers, which brings the drm_crtc_vblank_reset() back. v5: also mention rcar-du and ompadrm in the proper commit message above (Laurent). Reviewed-by: Laurent Pinchart Acked-by: Maxime Ripard Cc: Laurent Pinchart Reviewed-by: Boris Brezillon Acked-by: Liviu Dudau Acked-by: Thierry Reding Link: https://syzkaller.appspot.com/bug?id=0ba17d70d062b2595e1f061231474800f076c7cb Reported-by: Tetsuo Handa Reported-by: syzbot+0871b14ca2e2fb64f6e3@syzkaller.appspotmail.com Cc: Tetsuo Handa Cc: "James (Qian) Wang" Cc: Liviu Dudau Cc: Mihail Atanassov Cc: Brian Starkey Cc: Sam Ravnborg Cc: Boris Brezillon Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Ludovic Desroches Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Daniel Vetter Cc: Thierry Reding Cc: Jonathan Hunter Cc: Jyri Sarha Cc: Tomi Valkeinen Cc: Rob Clark Cc: Sean Paul Cc: Brian Masney Cc: Emil Velikov Cc: zhengbin Cc: Thomas Gleixner Cc: linux-tegra@vger.kernel.org Cc: Kieran Bingham Cc: linux-arm-kernel@lists.infradead.org Cc: linux-renesas-soc@vger.kernel.org Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200612160056.2082681-1-daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_atomic_state_helper.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/gpu/drm/drm_atomic_state_helper.c') diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c index 8fce6a115dfe..9ad74045158e 100644 --- a/drivers/gpu/drm/drm_atomic_state_helper.c +++ b/drivers/gpu/drm/drm_atomic_state_helper.c @@ -32,6 +32,7 @@ #include #include #include +#include #include #include @@ -93,6 +94,9 @@ __drm_atomic_helper_crtc_reset(struct drm_crtc *crtc, if (crtc_state) __drm_atomic_helper_crtc_state_reset(crtc_state, crtc); + if (drm_dev_has_vblank(crtc->dev)) + drm_crtc_vblank_reset(crtc); + crtc->state = crtc_state; } EXPORT_SYMBOL(__drm_atomic_helper_crtc_reset); -- cgit