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Brian Norris 9b78ee2341 drm/bridge: analogix_dp: Make PSR-exit block less 
commit c4c6ef2295 upstream.

Prior to commit 6c836d965b ("drm/rockchip: Use the helpers for PSR"),
"PSR exit" used non-blocking analogix_dp_send_psr_spd(). The refactor
started using the blocking variant, for a variety of reasons -- quoting
Sean Paul's potentially-faulty memory:

"""
 - To avoid racing a subsequent PSR entry (if exit takes a long time)
 - To avoid racing disable/modeset
 - We're not displaying new content while exiting PSR anyways, so there
   is minimal utility in allowing frames to be submitted
 - We're lying to userspace telling them frames are on the screen when
   we're just dropping them on the floor
"""

However, I'm finding that this blocking transition is causing upwards of
60+ ms of unneeded latency on PSR-exit, to the point that initial cursor
movements when leaving PSR are unbearably jumpy.

It turns out that we need to meet in the middle somewhere: Sean is right
that we were "lying to userspace" with a non-blocking PSR-exit, but the
new blocking behavior is also waiting too long:

According to the eDP specification, the sink device must support PSR
entry transitions from both state 4 (ACTIVE_RESYNC) and state 0
(INACTIVE). It also states that in ACTIVE_RESYNC, "the Sink device must
display the incoming active frames from the Source device with no
visible glitches and/or artifacts."

Thus, for our purposes, we only need to wait for ACTIVE_RESYNC before
moving on; we are ready to display video, and subsequent PSR-entry is
safe.

Tested on a Samsung Chromebook Plus (i.e., Rockchip RK3399 Gru Kevin),
where this saves about 60ms of latency, for PSR-exit that used to
take about 80ms.

Fixes: 6c836d965b ("drm/rockchip: Use the helpers for PSR")
Cc: <stable@vger.kernel.org>
Cc: Zain Wang <wzz@rock-chips.com>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211103135112.v3.1.I67612ea073c3306c71b46a87be894f79707082df@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-27 10:54:25 +01:00
arch s390/mm: fix 2KB pgtable release race 2022-01-27 10:54:25 +01:00
block scsi: block: pm: Always set request queue runtime active in blk_post_runtime_resume() 2022-01-27 10:54:08 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:50:29 +02:00
crypto crypto: jitter - consider 32 LSB for APT 2022-01-27 10:54:12 +01:00
Documentation counter: stm32-lptimer-cnt: remove iio counter abi 2022-01-27 10:54:08 +01:00
drivers drm/bridge: analogix_dp: Make PSR-exit block less 2022-01-27 10:54:25 +01:00
fs fuse: Pass correct lend value to filemap_write_and_wait_range() 2022-01-27 10:54:25 +01:00
include ACPICA: actypes.h: Expand the ACPI_ACCESS_ definitions 2022-01-27 10:54:18 +01:00
init bpf: Add kconfig knob for disabling unpriv bpf by default 2022-01-05 12:40:34 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:19:10 +01:00
kernel tracing/kprobes: 'nmissed' not showed correctly for kretprobe 2022-01-27 10:54:25 +01:00
lib lib/mpi: Add the return value check of kcalloc() 2022-01-27 10:54:02 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode 2022-01-27 10:53:44 +01:00
net mac80211: allow non-standard VHT MCS-10/11 2022-01-27 10:54:19 +01:00
samples ftrace/samples: Add missing prototypes direct functions 2022-01-11 15:25:00 +01:00
scripts recordmcount.pl: fix typo in s390 mcount regex 2022-01-05 12:40:29 +01:00
security selinux: fix potential memleak in selinux_add_opt() 2022-01-27 10:53:58 +01:00
sound ASoC: mediatek: mt8183: fix device_node leak 2022-01-27 10:54:24 +01:00
tools selftests/powerpc/spectre_v2: Return skip code when miss_percent is high 2022-01-27 10:54:23 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-12-22 09:30:50 +01:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.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 kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 MAINTAINERS: adjust GCC PLUGINS after gcc-plugin.sh removal 2021-12-14 11:32:46 +01:00
Makefile Linux 5.10.93 2022-01-20 09:17:52 +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.