• Daniel Vetter's avatar
    drm/atomic-helper: reset vblank on crtc reset · 51f644b4
    Daniel Vetter authored
    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: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
    Acked-by: default avatarMaxime Ripard <mripard@kernel.org>
    Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
    Acked-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
    Acked-by: default avatarThierry Reding <treding@nvidia.com>
    Link: https://syzkaller.appspot.com/bug?id=0ba17d70d062b2595e1f061231474800f076c7cbReported-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Reported-by: syzbot+0871b14ca2e2fb64f6e3@syzkaller.appspotmail.com
    Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: "James (Qian) Wang" <james.qian.wang@arm.com>
    Cc: Liviu Dudau <liviu.dudau@arm.com>
    Cc: Mihail Atanassov <mihail.atanassov@arm.com>
    Cc: Brian Starkey <brian.starkey@arm.com>
    Cc: Sam Ravnborg <sam@ravnborg.org>
    Cc: Boris Brezillon <bbrezillon@kernel.org>
    Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
    Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
    Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
    Cc: Maxime Ripard <mripard@kernel.org>
    Cc: Thomas Zimmermann <tzimmermann@suse.de>
    Cc: David Airlie <airlied@linux.ie>
    Cc: Daniel Vetter <daniel@ffwll.ch>
    Cc: Thierry Reding <thierry.reding@gmail.com>
    Cc: Jonathan Hunter <jonathanh@nvidia.com>
    Cc: Jyri Sarha <jsarha@ti.com>
    Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
    Cc: Rob Clark <robdclark@gmail.com>
    Cc: Sean Paul <seanpaul@chromium.org>
    Cc: Brian Masney <masneyb@onstation.org>
    Cc: Emil Velikov <emil.velikov@collabora.com>
    Cc: zhengbin <zhengbin13@huawei.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-tegra@vger.kernel.org
    Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: linux-renesas-soc@vger.kernel.org
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20200612160056.2082681-1-daniel.vetter@ffwll.ch
    51f644b4
omap_crtc.c 22.7 KB