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Douglas Anderson 906f7797a3 drm/msm/dp: Avoid unpowered AUX xfers that caused crashes [ Upstream commit `d03fcc1de0` ] If you happened to try to access `/dev/drm_dp_aux` devices provided by the MSM DP AUX driver too early at bootup you could go boom. Let's avoid that by only allowing AUX transfers when the controller is powered up. Specifically the crash that was seen (on Chrome OS 5.4 tree with relevant backports): Kernel panic - not syncing: Asynchronous SError Interrupt CPU: 0 PID: 3131 Comm: fwupd Not tainted 5.4.144-16620-g28af11b73efb #1 Hardware name: Google Lazor (rev3+) with KB Backlight (DT) Call trace: dump_backtrace+0x0/0x14c show_stack+0x20/0x2c dump_stack+0xac/0x124 panic+0x150/0x390 nmi_panic+0x80/0x94 arm64_serror_panic+0x78/0x84 do_serror+0x0/0x118 do_serror+0xa4/0x118 el1_error+0xbc/0x160 dp_catalog_aux_write_data+0x1c/0x3c dp_aux_cmd_fifo_tx+0xf0/0x1b0 dp_aux_transfer+0x1b0/0x2bc drm_dp_dpcd_access+0x8c/0x11c drm_dp_dpcd_read+0x64/0x10c auxdev_read_iter+0xd4/0x1c4 I did a little bit of tracing and found that: * We register the AUX device very early at bootup. * Power isn't actually turned on for my system until hpd_event_thread() -> dp_display_host_init() -> dp_power_init() * You can see that dp_power_init() calls dp_aux_init() which is where we start allowing AUX channel requests to go through. In general this patch is a bit of a bandaid but at least it gets us out of the current state where userspace acting at the wrong time can fully crash the system. * I think the more proper fix (which requires quite a bit more changes) is to power stuff on while an AUX transfer is happening. This is like the solution we did for ti-sn65dsi86. This might be required for us to move to populating the panel via the DP-AUX bus. * Another fix considered was to dynamically register / unregister. I tried that at <https://crrev.com/c/3169431/3> but it got ugly. Currently there's a bug where the pm_runtime() state isn't tracked properly and that causes us to just keep registering more and more. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com> Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> Link: https://lore.kernel.org/r/20211109100403.1.I4e23470d681f7efe37e2e7f1a6466e15e9bb1d72@changeid Signed-off-by: Rob Clark <robdclark@chromium.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-12-17 10:30:14 +01:00
arch	csky: fix typo of fpu config macro	2021-12-14 10:57:22 +01:00
block	block: fix ioprio_get(IOPRIO_WHO_PGRP) vs setuid(2)	2021-12-14 10:57:16 +01:00
certs	certs: Add support for using elliptic curve keys for signing modules	2021-08-23 19:55:42 +03:00
crypto	crypto: pcrypt - Delay write to padata->info	2021-11-18 19:16:44 +01:00
Documentation	dt-bindings: media: nxp,imx7-mipi-csi2: Drop bad if/then schema	2021-12-17 10:30:13 +01:00
drivers	drm/msm/dp: Avoid unpowered AUX xfers that caused crashes	2021-12-17 10:30:14 +01:00
fs	netfs: Fix lockdep warning from taking sb_writers whilst holding mmap_lock	2021-12-17 10:30:13 +01:00
include	bus: mhi: core: Add support for forced PM resume	2021-12-14 10:57:22 +01:00
init	init: make unknown command line param message clearer	2021-11-18 19:17:11 +01:00
ipc	shm: extend forced shm destroy to support objects from several IPC nses	2021-11-25 09:48:42 +01:00
kernel	wait: add wake_up_pollfree()	2021-12-14 10:57:15 +01:00
lib	siphash: use _unaligned version by default	2021-12-08 09:04:47 +01:00
LICENSES	LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"	2021-07-15 06:31:24 -06:00
mm	mm: bdi: initialize bdi_min_ratio when bdi is unregistered	2021-12-14 10:57:11 +01:00
net	inet: use #ifdef CONFIG_SOCK_RX_QUEUE_MAPPING consistently	2021-12-17 10:30:13 +01:00
samples	samples/bpf: Fix incorrect use of strlen in xdp_redirect_cpu	2021-11-25 09:48:33 +01:00
scripts	leaking_addresses: Always print a trailing newline	2021-11-18 19:16:16 +01:00
security	selinux: fix NULL-pointer dereference when hashtab allocation fails	2021-11-25 09:49:07 +01:00
sound	ASoC: codecs: wcd934x: return correct value from mixer put	2021-12-14 10:57:17 +01:00
tools	perf bpf_skel: Do not use typedef to avoid error on old clang	2021-12-17 10:30:13 +01:00
usr	.gitignore: prefix local generated files with a slash	2021-05-02 00:43:35 +09:00
virt	KVM: Ensure local memslot copies operate on up-to-date arch-specific data	2021-12-08 09:04:43 +01:00
.clang-format	clang-format: Update with the latest for_each macro list	2021-05-12 23:32:39 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	.gitignore: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: add Andrej Shadura	2021-10-18 20:22:03 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Daniel Drake to credits	2021-09-21 08:34:58 +03:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	drm fixes for 5.15 final	2021-10-28 12:17:01 -07:00
Makefile	Linux 5.15.9	2021-12-16 15:17:49 +01:00
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.