From 27655b9bb9f0d9c32b8de8bec649b676898c52d5 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Mon, 10 Jul 2023 11:10:17 +0200 Subject: drm/client: Send hotplug event after registering a client MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Generate a hotplug event after registering a client to allow the client to configure its display. Remove the hotplug calls from the existing clients for fbdev emulation. This change fixes a concurrency bug between registering a client and receiving events from the DRM core. The bug is present in the fbdev emulation of all drivers. The fbdev emulation currently generates a hotplug event before registering the client to the device. For each new output, the DRM core sends an additional hotplug event to each registered client. If the DRM core detects first output between sending the artificial hotplug and registering the device, the output's hotplug event gets lost. If this is the first output, the fbdev console display remains dark. This has been observed with amdgpu and fbdev-generic. Fix this by adding hotplug generation directly to the client's register helper drm_client_register(). Registering the client and receiving events are serialized by struct drm_device.clientlist_mutex. So an output is either configured by the initial hotplug event, or the client has already been registered. The bug was originally added in commit 6e3f17ee73f7 ("drm/fb-helper: generic: Call drm_client_add() after setup is done"), in which adding a client and receiving a hotplug event switched order. It was hidden, as most hardware and drivers have at least on static output configured. Other drivers didn't use the internal DRM client or still had struct drm_mode_config_funcs.output_poll_changed set. That callback handled hotplug events as well. After not setting the callback in amdgpu in commit 0e3172bac3f4 ("drm/amdgpu: Don't set struct drm_driver.output_poll_changed"), amdgpu did not show a framebuffer console if output events got lost. The bug got copy-pasted from fbdev-generic into the other fbdev emulation. Reported-by: Moritz Duge Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2649 Fixes: 6e3f17ee73f7 ("drm/fb-helper: generic: Call drm_client_add() after setup is done") Fixes: 8ab59da26bc0 ("drm/fb-helper: Move generic fbdev emulation into separate source file") Fixes: b79fe9abd58b ("drm/fbdev-dma: Implement fbdev emulation for GEM DMA helpers") Fixes: 63c381552f69 ("drm/armada: Implement fbdev emulation as in-kernel client") Fixes: 49953b70e7d3 ("drm/exynos: Implement fbdev emulation as in-kernel client") Fixes: 8f1aaccb04b7 ("drm/gma500: Implement client-based fbdev emulation") Fixes: 940b869c2f2f ("drm/msm: Implement fbdev emulation as in-kernel client") Fixes: 9e69bcd88e45 ("drm/omapdrm: Implement fbdev emulation as in-kernel client") Fixes: e317a69fe891 ("drm/radeon: Implement client-based fbdev emulation") Fixes: 71ec16f45ef8 ("drm/tegra: Implement fbdev emulation as in-kernel client") Fixes: 0e3172bac3f4 ("drm/amdgpu: Don't set struct drm_driver.output_poll_changed") Signed-off-by: Thomas Zimmermann Tested-by: Moritz Duge Tested-by: Torsten Krah Tested-by: Paul Schyska Cc: Daniel Vetter Cc: David Airlie Cc: Noralf Trønnes Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Javier Martinez Canillas Cc: Russell King Cc: Inki Dae Cc: Seung-Woo Kim Cc: Kyungmin Park Cc: Krzysztof Kozlowski Cc: Patrik Jakobsson Cc: Rob Clark Cc: Abhinav Kumar Cc: Dmitry Baryshkov Cc: Tomi Valkeinen Cc: Alex Deucher Cc: "Christian König" Cc: "Pan, Xinhui" Cc: Thierry Reding Cc: Mikko Perttunen Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-arm-msm@vger.kernel.org Cc: freedreno@lists.freedesktop.org Cc: amd-gfx@lists.freedesktop.org Cc: linux-tegra@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: # v5.2+ Reviewed-by: Javier Martinez Canillas Reviewed-by: Dmitry Baryshkov # msm Link: https://patchwork.freedesktop.org/patch/msgid/20230710091029.27503-1-tzimmermann@suse.de --- drivers/gpu/drm/tegra/fbdev.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'drivers/gpu/drm/tegra') diff --git a/drivers/gpu/drm/tegra/fbdev.c b/drivers/gpu/drm/tegra/fbdev.c index e74d9be981c7..d042234e1807 100644 --- a/drivers/gpu/drm/tegra/fbdev.c +++ b/drivers/gpu/drm/tegra/fbdev.c @@ -225,10 +225,6 @@ void tegra_fbdev_setup(struct drm_device *dev) if (ret) goto err_drm_client_init; - ret = tegra_fbdev_client_hotplug(&helper->client); - if (ret) - drm_dbg_kms(dev, "client hotplug ret=%d\n", ret); - drm_client_register(&helper->client); return; -- cgit