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Maxime Chevallier a1ae283929 net: mdio: mdio-i2c: Hold the i2c bus lock during smbus transactions
[ Upstream commit 4dc8b26a3a ]

When accessing an MDIO register using single-byte smbus accesses, we have to
perform 2 consecutive operations targeting the same address,
first accessing the MSB then the LSB of the 16 bit register:

  read_1_byte(addr); <- returns MSB of register at address 'addr'
  read_1_byte(addr); <- returns LSB

Some PHY devices present in SFP such as the Broadcom 5461 don't like
seeing foreign i2c transactions in-between these 2 smbus accesses, and
will return the MSB a second time when trying to read the LSB :

  read_1_byte(addr); <- returns MSB

  	i2c_transaction_for_other_device_on_the_bus();

  read_1_byte(addr); <- returns MSB again

Given the already fragile nature of accessing PHYs/SFPs with single-byte
smbus accesses, it's safe to say that this Broadcom PHY may not be the
only one acting like this.

Let's therefore hold the i2c bus lock while performing our smbus
transactions to avoid interleaved accesses.

Fixes: d4bd3aca33 ("net: mdio: mdio-i2c: Add support for single-byte SMBus operations")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251003070311.861135-1-maxime.chevallier@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-19 16:37:12 +02:00
arch LoongArch: Init acpi_gbl_use_global_lock to false 2025-10-19 16:37:08 +02:00
block blk-throttle: fix throtl_data leak during disk release 2025-10-15 12:03:34 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto KEYS: X.509: Fix Basic Constraints CA flag parsing 2025-10-15 12:04:11 +02:00
Documentation Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram 2025-10-15 12:04:01 +02:00
drivers net: mdio: mdio-i2c: Hold the i2c bus lock during smbus transactions 2025-10-19 16:37:12 +02:00
fs nfsd: fix timestamp updates in CB_GETATTR 2025-10-19 16:37:06 +02:00
include vfs: add ATTR_CTIME_SET flag 2025-10-19 16:37:06 +02:00
init Fix CC_HAS_ASM_GOTO_OUTPUT on non-x86 architectures 2025-10-15 12:03:13 +02:00
io_uring io_uring/zcrx: fix overshooting recv limit 2025-10-15 12:04:15 +02:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel rseq: Protect event mask against membarrier IPI 2025-10-19 16:36:59 +02:00
lib vdso/datastore: Gate time data behind CONFIG_GENERIC_GETTIMEOFDAY 2025-10-15 12:03:24 +02:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm memcg: skip cgroup_file_notify if spinning is not allowed 2025-10-19 16:37:00 +02:00
net bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6} 2025-10-19 16:37:11 +02:00
rust cpufreq: Make drivers using CPUFREQ_ETERNAL specify transition latency 2025-10-19 16:37:00 +02:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts scripts/misc-check: update export checks for EXPORT_SYMBOL_FOR_MODULES() 2025-10-15 12:03:22 +02:00
security lsm: CONFIG_LSM can depend on CONFIG_SECURITY 2025-10-15 12:03:17 +02:00
sound ASoC: SOF: Intel: Read the LLP via the associated Link DMA channel 2025-10-19 16:37:09 +02:00
tools perf tools: Fix arm64 libjvmti build by generating unistd_64.h 2025-10-19 16:37:11 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.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: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap 7 hotfixes. 4 are cc:stable and the remainder address post-6.16 issues or 2025-09-28 09:32:00 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -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: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc8 2025-09-28 13:19:23 -07:00
Makefile Linux 6.17.3 2025-10-15 12:04:23 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.