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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 <laurent.pinchart@ideasonboard.com> Acked-by: Maxime Ripard <mripard@kernel.org> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> Acked-by: Liviu Dudau <liviu.dudau@arm.com> Acked-by: Thierry Reding <treding@nvidia.com> Link: https://syzkaller.appspot.com/bug?id=0ba17d70d062b2595e1f061231474800f076c7cb Reported-by: Tetsuo 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: Daniel Vetter <daniel.vetter@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200612160056.2082681-1-daniel.vetter@ffwll.ch |
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| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
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| mm | ||
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| usr | ||
| virt | ||
| .clang-format | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.