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Thomas Zimmermann aa87c43ea5 drm/client: Send hotplug event after registering a client 
commit 27655b9bb9 upstream.

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 6e3f17ee73 ("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 0e3172bac3 ("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 <MoritzDuge@kolahilft.de>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2649
Fixes: 6e3f17ee73 ("drm/fb-helper: generic: Call drm_client_add() after setup is done")
Fixes: 8ab59da26b ("drm/fb-helper: Move generic fbdev emulation into separate source file")
Fixes: b79fe9abd5 ("drm/fbdev-dma: Implement fbdev emulation for GEM DMA helpers")
Fixes: 63c381552f ("drm/armada: Implement fbdev emulation as in-kernel client")
Fixes: 49953b70e7 ("drm/exynos: Implement fbdev emulation as in-kernel client")
Fixes: 8f1aaccb04 ("drm/gma500: Implement client-based fbdev emulation")
Fixes: 940b869c2f ("drm/msm: Implement fbdev emulation as in-kernel client")
Fixes: 9e69bcd88e ("drm/omapdrm: Implement fbdev emulation as in-kernel client")
Fixes: e317a69fe8 ("drm/radeon: Implement client-based fbdev emulation")
Fixes: 71ec16f45e ("drm/tegra: Implement fbdev emulation as in-kernel client")
Fixes: 0e3172bac3 ("drm/amdgpu: Don't set struct drm_driver.output_poll_changed")
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Moritz Duge <MoritzDuge@kolahilft.de>
Tested-by: Torsten Krah <krah.tm@gmail.com>
Tested-by: Paul Schyska <pschyska@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@gmail.com>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Mikko Perttunen <mperttunen@nvidia.com>
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: <stable@vger.kernel.org> # v5.2+
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # msm
Link: https://patchwork.freedesktop.org/patch/msgid/20230710091029.27503-1-tzimmermann@suse.de
[ Dropped changes to drivers/gpu/drm/armada/armada_fbdev.c as
  174c3c38e3 drm/armada: Initialize fbdev DRM client
  was introduced in 6.5-rc1 ]
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-07-23 13:53:50 +02:00
arch riscv: mm: fix truncation warning on RV32 2023-07-23 13:53:48 +02:00
block blk-crypto: use dynamic lock class for blk_crypto_profile::lock 2023-07-23 13:53:39 +02:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:36:19 +02:00
Documentation fs: Lock moved directories 2023-07-19 16:36:55 +02:00
drivers drm/client: Send hotplug event after registering a client 2023-07-23 13:53:50 +02:00
fs smb: client: fix parsing of source mount option 2023-07-23 13:53:50 +02:00
include net/sched: make psched_mtu() RTNL-less safe 2023-07-23 13:53:49 +02:00
init kbuild: Fix CFI failures with GCOV 2023-07-19 16:36:23 +02:00
io_uring io_uring: Use io_schedule* in cqring wait 2023-07-19 16:37:03 +02:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel bpf: cpumap: Fix memory leak in cpu_map_update_elem 2023-07-23 13:53:47 +02:00
lib lib: dhry: fix sleeping allocations inside non-preemptable section 2023-07-19 16:36:50 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm shmem: use ramfs_kill_sb() for kill_sb method of ramfs-based tmpfs 2023-07-19 16:36:54 +02:00
net net/sched: sch_qfq: account for stab overhead in qfq_enqueue 2023-07-23 13:53:49 +02:00
rust Rust changes for v6.4 2023-04-30 11:20:22 -07:00
samples samples/bpf: xdp1 and xdp2 reduce XDPBUFSIZE to 60 2023-07-19 16:35:25 +02:00
scripts kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS 2023-07-19 16:37:00 +02:00
security security/integrity: fix pointer to ESL data and its size on pseries 2023-07-23 13:53:34 +02:00
sound ASoC: mediatek: mt8173: Fix snd_soc_component_initialize error path 2023-07-19 16:36:58 +02:00
tools wireguard: netlink: send staged packets when setting initial private key 2023-07-19 16:37:02 +02:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: Avoid illegal stage2 mapping on invalid memory slot 2023-06-22 15:14:57 -04:00
.clang-format cxl for v6.4 2023-04-30 11:51:51 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore linux-kselftest-kunit-6.4-rc1 2023-04-24 12:31:32 -07:00
.mailmap mailmap: add entries for Ben Dooks 2023-06-19 13:19:35 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: sctp: move Neil to CREDITS 2023-05-12 08:51:32 +01:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking fixes for 6.4-rc8, including fixes from ipsec, bpf, 2023-06-22 17:59:51 -07:00
Makefile Linux 6.4.4 2023-07-19 16:37:03 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.