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Michael Walle ff3d5d04db
drm: bridge: samsung-dsim: Don't use FORCE_STOP_STATE
The FORCE_STOP_STATE bit is unsuitable to force the DSI link into LP-11
mode. It seems the bridge internally queues DSI packets and when the
FORCE_STOP_STATE bit is cleared, they are sent in close succession
without any useful timing (this also means that the DSI lanes won't go
into LP-11 mode). The length of this gibberish varies between 1ms and
5ms. This sometimes breaks an attached bridge (TI SN65DSI84 in this
case). In our case, the bridge will fail in about 1 per 500 reboots.

The FORCE_STOP_STATE handling was introduced to have the DSI lanes in
LP-11 state during the .pre_enable phase. But as it turns out, none of
this is needed at all. Between samsung_dsim_init() and
samsung_dsim_set_display_enable() the lanes are already in LP-11 mode.
The code as it was before commit 20c827683d ("drm: bridge:
samsung-dsim: Fix init during host transfer") and 0c14d31306 ("drm:
bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") was correct
in this regard.

This patch basically reverts both commits. It was tested on an i.MX8M
SoC with an SN65DSI84 bridge. The signals were probed and the DSI
packets were decoded during initialization and link start-up. After this
patch the first DSI packet on the link is a VSYNC packet and the timing
is correct.

Command mode between .pre_enable and .enable was also briefly tested by
a quick hack. There was no DSI link partner which would have responded,
but it was made sure the DSI packet was send on the link. As a side
note, the command mode seems to just work in HS mode. I couldn't find
that the bridge will handle commands in LP mode.

Fixes: 20c827683d ("drm: bridge: samsung-dsim: Fix init during host transfer")
Fixes: 0c14d31306 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec")
Signed-off-by: Michael Walle <mwalle@kernel.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231113164344.1612602-1-mwalle@kernel.org
2024-01-26 22:48:47 +09:00
arch powerpc fixes for 6.8 #2 2024-01-21 11:04:29 -08:00
block for-6.8/block-2024-01-18 2024-01-18 18:22:40 -08:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: scomp - fix req->dst buffer overflow 2023-12-29 11:25:56 +08:00
Documentation Updates for time and clocksources: 2024-01-21 11:14:40 -08:00
drivers drm: bridge: samsung-dsim: Don't use FORCE_STOP_STATE 2024-01-26 22:48:47 +09:00
fs More bcachefs updates for 6.7-rc1 2024-01-21 14:01:12 -08:00
include accel/ivpu: Deprecate DRM_IVPU_PARAM_CONTEXT_PRIORITY param 2024-01-22 10:31:54 +01:00
init Driver core changes for 6.8-rc1 2024-01-18 09:48:40 -08:00
io_uring for-6.8/io_uring-2024-01-18 2024-01-18 18:17:57 -08:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel Updates for time and clocksources: 2024-01-21 11:14:40 -08:00
lib RISC-V Patches for the 6.8 Merge Window, Part 4 2024-01-20 11:06:04 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm vfs-6.8.netfs 2024-01-19 09:10:23 -08:00
net Assorted CephFS fixes and cleanups with nothing standing out. 2024-01-19 09:58:55 -08:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples RISC-V Patches for the 6.8 Merge Window, Part 4 2024-01-20 11:06:04 -08:00
scripts Coccinelle change for v6.8 2024-01-20 14:20:34 -08:00
security + Features 2024-01-19 10:53:55 -08:00
sound sound fixes for 6.8-rc1 2024-01-19 12:30:29 -08:00
tools RISC-V Patches for the 6.8 Merge Window, Part 4 2024-01-20 11:06:04 -08:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt Generic: 2024-01-17 13:03:37 -08:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap Char/Misc and other Driver changes for 6.8-rc1 2024-01-17 16:47:17 -08:00
.rustfmt.toml
COPYING
CREDITS Including fixes from bpf and netfilter. 2024-01-18 17:33:50 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS Various smb client fixes, including multichannel and for SMB3.1.1 POSIX extensions 2024-01-20 16:48:07 -08:00
Makefile Linux 6.8-rc1 2024-01-21 14:11:32 -08:00
README

Linux kernel
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