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Brian Norris 95df03b471 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 11:05:11 +01:00
arch s390/mm: fix 2KB pgtable release race 2022-01-27 11:05:10 +01:00
block block: check minor range in device_add_disk() 2022-01-27 11:04:48 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: jitter - consider 32 LSB for APT 2022-01-27 11:04:31 +01:00
Documentation HID: i2c-hid-of: Expose the touchscreen-inverted properties 2022-01-27 11:04:41 +01:00
drivers drm/bridge: analogix_dp: Make PSR-exit block less 2022-01-27 11:05:11 +01:00
fs fuse: Pass correct lend value to filemap_write_and_wait_range() 2022-01-27 11:05:08 +01:00
include udp6: Use Segment Routing Header for dest address if present 2022-01-27 11:05:05 +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 tracing: Have syscall trace events use trace_event_buffer_lock_reserve() 2022-01-27 11:05:09 +01:00
lib kunit: Don't crash if no parameters are generated 2022-01-27 11:04:40 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode 2022-01-27 11:03:01 +01:00
net udp6: Use Segment Routing Header for dest address if present 2022-01-27 11:05:05 +01:00
samples samples: bpf: Fix 'unknown warning group' build warning on Clang 2022-01-27 11:03:29 +01:00
scripts recordmcount.pl: fix typo in s390 mcount regex 2022-01-05 12:42:33 +01:00
security selinux: fix potential memleak in selinux_add_opt() 2022-01-27 11:03:43 +01:00
sound ASoC: mediatek: mt8183: fix device_node leak 2022-01-27 11:05:04 +01:00
tools selftests/powerpc: Add a test of sigreturning to the kernel 2022-01-27 11:05:03 +01:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-12-22 09:32:34 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.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 5.15.16 2022-01-20 09:13:16 +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.