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Christian Marangi d04084d09f net: dsa: qca8k: enable use_single_write for qca8xxx 
commit 2c39dd025d upstream.

The qca8xxx switch supports 2 way to write reg values, a slow way using
mdio and a fast way by sending specially crafted mgmt packet to
read/write reg.

The fast way can support up to 32 bytes of data as eth packet are used
to send/receive.

This correctly works for almost the entire regmap of the switch but with
the use of some kernel selftests for dsa drivers it was found a funny
and interesting hw defect/limitation.

For some specific reg, bulk write won't work and will result in writing
only part of the requested regs resulting in half data written. This was
especially hard to track and discover due to the total strangeness of
the problem and also by the specific regs where this occurs.

This occurs in the specific regs of the ATU table, where multiple entry
needs to be written to compose the entire entry.
It was discovered that with a bulk write of 12 bytes on
QCA8K_REG_ATU_DATA0 only QCA8K_REG_ATU_DATA0 and QCA8K_REG_ATU_DATA2
were written, but QCA8K_REG_ATU_DATA1 was always zero.
Tcpdump was used to make sure the specially crafted packet was correct
and this was confirmed.

The problem was hard to track as the lack of QCA8K_REG_ATU_DATA1
resulted in an entry somehow possible as the first bytes of the mac
address are set in QCA8K_REG_ATU_DATA0 and the entry type is set in
QCA8K_REG_ATU_DATA2.

Funlly enough writing QCA8K_REG_ATU_DATA1 results in the same problem
with QCA8K_REG_ATU_DATA2 empty and QCA8K_REG_ATU_DATA1 and
QCA8K_REG_ATU_FUNC correctly written.
A speculation on the problem might be that there are some kind of
indirection internally when accessing these regs and they can't be
accessed all together, due to the fact that it's really a table mapped
somewhere in the switch SRAM.

Even more funny is the fact that every other reg was tested with all
kind of combination and they are not affected by this problem. Read
operation was also tested and always worked so it's not affected by this
problem.

The problem is not present if we limit writing a single reg at times.

To handle this hardware defect, enable use_single_write so that bulk
api can correctly split the write in multiple different operation
effectively reverting to a non-bulk write.

Cc: Mark Brown <broonie@kernel.org>
Fixes: c766e077d9 ("net: dsa: qca8k: convert to regmap read/write API")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-08-03 10:26:09 +02:00
arch x86/cpu: Enable STIBP on AMD if Automatic IBRS is enabled 2023-08-03 10:26:08 +02:00
block blk-mq: Fix stall due to recursive flush plug 2023-08-03 10:25:41 +02:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:36:19 +02:00
Documentation xen: speed up grant-table reclaim 2023-08-03 10:26:09 +02:00
drivers net: dsa: qca8k: enable use_single_write for qca8xxx 2023-08-03 10:26:09 +02:00
fs proc/vmcore: fix signedness bug in read_from_oldmem() 2023-08-03 10:26:09 +02:00
include block: Fix a source code comment in include/uapi/linux/blkzoned.h 2023-08-03 10:25:57 +02:00
init kbuild: Fix CFI failures with GCOV 2023-07-19 16:36:23 +02:00
io_uring io_uring: don't audit the capability check in io_uring_create() 2023-08-03 10:25:42 +02:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel locking/rtmutex: Fix task->pi_waiters integrity 2023-08-03 10:26:09 +02:00
lib maple_tree: fix 32 bit mas_next testing 2023-08-03 10:25:46 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/mlock: fix vma iterator conversion of apply_vma_lock_flags() 2023-07-27 08:56:32 +02:00
net tipc: stop tipc crypto on failure in tipc_node_create 2023-08-03 10:25:54 +02:00
rust Rust changes for v6.4 2023-04-30 11:20:22 -07:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:54:09 +02:00
scripts kbuild: rust: avoid creating temporary files 2023-07-27 08:57:06 +02:00
security security: keys: Modify mismatched function name 2023-07-27 08:56:59 +02:00
sound ALSA: hda/relatek: Enable Mute LED on HP 250 G8 2023-08-03 10:26:06 +02:00
tools tools: ynl-gen: fix enum index in _decode_enum(..) 2023-08-03 10:25:53 +02:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:26:01 +02:00
.clang-format cxl for v6.4 2023-04-30 11:51:51 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore linux-kselftest-kunit-6.4-rc1 2023-04-24 12:31:32 -07:00
.mailmap mailmap: add entries for Ben Dooks 2023-06-19 13:19:35 -07:00
.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: sctp: move Neil to CREDITS 2023-05-12 08:51:32 +01:00
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 Networking fixes for 6.4-rc8, including fixes from ipsec, bpf, 2023-06-22 17:59:51 -07:00
Makefile Linux 6.4.7 2023-07-27 08:57:07 +02:00
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.