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Marc Kleine-Budde 30447a1bc0 can: mcp251xfd: mcp251xfd_get_tef_len(): work around erratum DS80000789E 6. 
Commit b8e0ddd36c ("can: mcp251xfd: tef: prepare to workaround
broken TEF FIFO tail index erratum") introduced
mcp251xfd_get_tef_len() to get the number of unhandled transmit events
from the Transmit Event FIFO (TEF).

As the TEF has no head index, the driver uses the TX-FIFO's tail index
instead, assuming that send frames are completed.

When calculating the number of unhandled TEF events, that commit
didn't take mcp2518fd erratum DS80000789E 6. into account. According
to that erratum, the FIFOCI bits of a FIFOSTA register, here the
TX-FIFO tail index might be corrupted.

However here it seems the bit indicating that the TX-FIFO is
empty (MCP251XFD_REG_FIFOSTA_TFERFFIF) is not correct while the
TX-FIFO tail index is.

Assume that the TX-FIFO is indeed empty if:
- Chip's head and tail index are equal (len == 0).
- The TX-FIFO is less than half full.
  (The TX-FIFO empty case has already been checked at the
   beginning of this function.)
- No free buffers in the TX ring.

If the TX-FIFO is assumed to be empty, assume that the TEF is full and
return the number of elements in the TX-FIFO (which equals the number
of TEF elements).

If these assumptions are false, the driver might read to many objects
from the TEF. mcp251xfd_handle_tefif_one() checks the sequence numbers
and will refuse to process old events.

Reported-by: Renjaya Raga Zenta <renjaya.zenta@formulatrix.com>
Closes: https://patch.msgid.link/CAJ7t6HgaeQ3a_OtfszezU=zB-FqiZXqrnATJ3UujNoQJJf7GgA@mail.gmail.com
Fixes: b8e0ddd36c ("can: mcp251xfd: tef: prepare to workaround broken TEF FIFO tail index erratum")
Tested-by: Renjaya Raga Zenta <renjaya.zenta@formulatrix.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20241126-mcp251xfd-fix-length-calculation-v2-1-c2ed516ed6ba@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
History 2024-11-26 11:42:32 +01:00
arch Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
block for-6.13/block-20241118 2024-11-18 16:50:08 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Random number generator updates for Linux 6.13-rc1. 2024-11-19 10:43:44 -08:00
Documentation Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
drivers can: mcp251xfd: mcp251xfd_get_tef_len(): work around erratum DS80000789E 6. 2024-11-26 11:42:32 +01:00
fs Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
include Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
init printk changes for 6.13 2024-11-20 09:21:11 -08:00
io_uring A rather large update for timekeeping and timers: 2024-11-19 16:35:06 -08:00
ipc fdget(), more trivial conversions 2024-11-03 01:28:06 -05:00
kernel Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
lib Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
net netlink: fix false positive warning in extack during dumps 2024-11-24 16:58:07 -08:00
rust Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
samples bpf-next-bpf-next-6.13 2024-11-21 08:11:04 -08:00
scripts bpf-next-bpf-next-6.13 2024-11-21 08:11:04 -08:00
security This update includes the following changes: 2024-11-19 10:28:41 -08:00
sound Devicetree updates for v6.13: 2024-11-20 13:19:25 -08:00
tools selftests: net: test extacks in netlink dumps 2024-11-24 17:00:06 -08:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt the bulk of struct fd memory safety stuff 2024-11-18 12:24:06 -08:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +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: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap media updates for v6.13-rc1 2024-11-20 14:01:15 -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 cgroup: Changes for v6.13 2024-11-20 09:54:49 -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 Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
Makefile Linux 6.12 2024-11-17 14:15:08 -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.