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Leo Li 2a2b7b6f90 drm/amd/display: Increase vblank offdelay for PSR panels 
commit f21e6d149b upstream.

[Why]

Depending on when the HW latching event (vupdate) of double-buffered
registers happen relative to the PSR SDP (signals panel psr enter/exit)
deadline, and how bad the Panel clock has drifted since the last ALPM
off event, there can be up to 3 frames of delay between sending the PSR
exit cmd to DMUB fw, and when the panel starts displaying live frames.
This can manifest as micro-stuttering when userspace commit patterns
cause rapid toggling of the DRM vblank counter, since PSR enter/exit is
hooked up to DRM vblank disable/enable respectively.

In the ideal world, the panel should present the live frame immediately
on PSR exit cmd. But due to HW design and PSR limitations, immediate
exit can only happen by chance, when:

1. PSR exit cmd is ack'd by FW before HW latching (vupdate) event, and
2. Panel's SDP deadline -- determined by it's PSR Start Delay in DPCD
  71h -- is after the vupdate event. The PSR exit SDP can then be sent
  immediately after HW latches. Otherwise, we have to wait 1 frame. And
3. There is negligible drift between the panel's clock and source clock.
  Otherwise, there can be up to 1 frame of drift.

Note that this delay is not expected with Panel Replay.

[How]

Since PSR power savings can be quite substantial, and there are a lot of
systems in the wild with PSR panels, It'll be nice to have a middle
ground that balances user experience with power savings.

A simple way to achieve this is by extending the vblank offdelay, such
that additional PSR exit delays will be less perceivable.

We can set:

   20/100 * offdelay_ms = 3_frames_ms
=> offdelay_ms = 5 * 3_frames_ms

This ensures that `3_frames_ms` will only be experienced as a 20% delay
on top how long the panel has been static, and thus make the delay
less perceivable.

If this ends up being too high of a percentage, it can be dropped
further in a future change.

Fixes: 537ef0f888 ("drm/amd/display: use new vblank enable policy for DCN35+")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-04-25 10:47:58 +02:00
arch perf/x86/intel/uncore: Fix the scale of IIO free running counters on SPR 2025-04-25 10:47:57 +02:00
block block: integrity: Do not call set_page_dirty_lock() 2025-04-25 10:47:50 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix larval relookup type and mask 2025-04-10 14:39:20 +02:00
Documentation netlink: specs: rt-link: adjust mctp attribute naming 2025-04-25 10:47:45 +02:00
drivers drm/amd/display: Increase vblank offdelay for PSR panels 2025-04-25 10:47:58 +02:00
fs virtiofs: add filesystem context source name check 2025-04-25 10:47:55 +02:00
include nfs: add missing selections of CONFIG_CRC32 2025-04-25 10:47:50 +02:00
init ARM: 9443/1: Require linker to support KEEP within OVERLAY for DCE 2025-04-10 14:39:40 +02:00
io_uring io_uring/kbuf: reject zero sized provided buffers 2025-04-20 10:15:40 +02:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel tracing: Fix filter string testing 2025-04-25 10:47:55 +02:00
lib string: Add load_unaligned_zeropad() code path to sized_strscpy() 2025-04-25 10:47:55 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm slab: ensure slab->obj_exts is clear in a newly allocated slab page 2025-04-25 10:47:55 +02:00
net Bluetooth: l2cap: Process valid commands in too long frame 2025-04-25 10:47:51 +02:00
rust rust: Fix enabling Rust and building with GCC for LoongArch 2025-04-10 14:39:36 +02:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts rust: kbuild: use pound to support GNU Make < 4.3 2025-04-25 10:47:49 +02:00
security landlock: Prepare to add second errata 2025-04-20 10:15:56 +02:00
sound ASoC: qcom: Fix sc7280 lpass potential buffer overflow 2025-04-25 10:47:50 +02:00
tools selftests/mm: generate a temporary mountpoint for cgroup filesystem 2025-04-25 10:47:54 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow building irqbypass.ko as as module when kvm.ko is a module 2025-04-20 10:15:54 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile rust: disable clippy::needless_continue 2025-04-25 10:47:49 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.