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35e282c186
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Luca Ceresoli 35e282c186
drm/bridge: ti-sn65dsi83: ignore PLL_UNLOCK errors 
On hardware based on Toradex Verdin AM62 the recovery mechanism added by
commit ad5c6ecef2 ("drm: bridge: ti-sn65dsi83: Add error recovery
mechanism") has been reported [0] to make the display turn on and off and
and the kernel logging "Unexpected link status 0x01".

According to the report, the error recovery mechanism is triggered by the
PLL_UNLOCK error going active. Analysis suggested the board is unable to
provide the correct DSI clock neede by the SN65DSI84, to which the TI
SN65DSI84 reacts by raising the PLL_UNLOCK, while the display still works
apparently without issues.

On other hardware, where all the clocks are within the components
specifications, the PLL_UNLOCK bit does not trigger while the display is in
normal use. It can trigger for e.g. electromagnetic interference, which is
a transient event and exactly the reason why the error recovery mechanism
has been implemented.

Idelly the PLL_UNLOCK bit could be ignored when working out of
specification, but this requires to detect in software whether it triggers
because the device is working out of specification but visually correctly
for the user or for good reasons (e.g. EMI, or even because working out of
specifications but compromising the visual output).

The ongoing analysis as of this writing [1][2] has not yet found a way for
the driver to discriminate among the two cases. So as a temporary measure
mask the PLL_UNLOCK error bit unconditionally.

[0] https://lore.kernel.org/r/bhkn6hley4xrol5o3ytn343h4unkwsr26p6s6ltcwexnrsjsdx@mgkdf6ztow42
[1] https://lore.kernel.org/all/b71e941c-fc8a-4ac1-9407-0fe7df73b412@gmail.com/
[2] https://lore.kernel.org/all/20251125103900.31750-1-francesco@dolcini.it/

Fixes: ad5c6ecef2 ("drm: bridge: ti-sn65dsi83: Add error recovery mechanism")
Closes: https://lore.kernel.org/r/bhkn6hley4xrol5o3ytn343h4unkwsr26p6s6ltcwexnrsjsdx@mgkdf6ztow42
Cc: stable@vger.kernel.org # 6.15+
Reported-by: João Paulo Gonçalves <joao.goncalves@toradex.com>
Tested-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Co-developed-by: Hervé Codina <herve.codina@bootlin.com>
Signed-off-by: Hervé Codina <herve.codina@bootlin.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://patch.msgid.link/20251127-drm-ti-sn65dsi83-ignore-pll-unlock-v1-1-8a03fdf562e9@bootlin.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>
2025-12-05 10:00:17 +01:00
arch 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
block block-6.18-20251031 2025-10-31 12:57:19 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation sound fixes for 6.18-rc6 2025-11-14 12:50:08 -08:00
drivers drm/bridge: ti-sn65dsi83: ignore PLL_UNLOCK errors 2025-12-05 10:00:17 +01:00
fs More NFS Client Bugfixes for Linux 6.18-rc 2025-11-14 13:44:23 -08:00
include 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs 2025-11-12 08:25:33 -07:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
lib lib/test_kho: check if KHO is enabled 2025-11-15 10:52:01 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
net bpf-fixes 2025-11-14 15:39:39 -08:00
rust rust: Add -fno-isolate-erroneous-paths-dereference to bindgen_skip_c_flags 2025-11-10 08:37:06 +08:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Rust fixes for v6.18 (2nd) 2025-11-14 15:36:15 -08:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound ALSA: usb-audio: Add native DSD quirks for PureAudio DAC series 2025-11-14 14:19:47 +01:00
tools perf tools fixes for v6.18: 2nd batch 2025-11-16 13:45:03 -08:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-04 09:16:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS 7 hotfixes. 5 are cc:stable, 4 are against mm/. 2025-11-16 13:31:14 -08:00
Makefile Linux 6.18-rc6 2025-11-16 14:25:38 -08:00
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.