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Siddharth Vadapalli e55273aa2a net: ethernet: ti: am65-cpsw: default to round-robin for host port receive 
commit 4a4d38ace1 upstream.

The Host Port (i.e. CPU facing port) of CPSW receives traffic from Linux
via TX DMA Channels which are Hardware Queues consisting of traffic
categorized according to their priority. The Host Port is configured to
dequeue traffic from these Hardware Queues on the basis of priority i.e.
as long as traffic exists on a Hardware Queue of a higher priority, the
traffic on Hardware Queues of lower priority isn't dequeued. An alternate
operation is also supported wherein traffic can be dequeued by the Host
Port in a Round-Robin manner.

Until commit under Fixes, the am65-cpsw driver enabled a single TX DMA
Channel, due to which, unless modified by user via "ethtool", all traffic
from Linux is transmitted on DMA Channel 0. Therefore, configuring
the Host Port for priority based dequeuing or Round-Robin operation
is identical since there is a single DMA Channel.

Since commit under Fixes, all 8 TX DMA Channels are enabled by default.
Additionally, the default "tc mapping" doesn't take into account
the possibility of different traffic profiles which various users
might have. This results in traffic starvation at the Host Port
due to the priority based dequeuing which has been enabled by default
since the inception of the driver. The traffic starvation triggers
NETDEV WATCHDOG timeout for all TX DMA Channels that haven't been serviced
due to the presence of traffic on the higher priority TX DMA Channels.

Fix this by defaulting to Round-Robin dequeuing at the Host Port, which
shall ensure that traffic is dequeued from all TX DMA Channels irrespective
of the traffic profile. This will address the NETDEV WATCHDOG timeouts.
At the same time, users can still switch from Round-Robin to Priority
based dequeuing at the Host Port with the help of the "p0-rx-ptype-rrobin"
private flag of "ethtool". Users are expected to setup an appropriate
"tc mapping" that suits their traffic profile when switching to priority
based dequeuing at the Host Port.

Fixes: be397ea347 ("net: ethernet: am65-cpsw: Set default TX channels to maximum")
Cc: <stable@vger.kernel.org>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Link: https://patch.msgid.link/20241220075618.228202-1-s-vadapalli@ti.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-01-09 13:33:52 +01:00
arch ARC: build: Try to guess GCC variant of cross compiler 2025-01-09 13:33:47 +01:00
block block: lift bio_is_zone_append to bio.h 2025-01-09 13:33:32 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ecdsa - Avoid signed integer overflow on signature decoding 2024-12-14 20:03:36 +01:00
Documentation dt-bindings: display: adi,adv7533: Drop single lane support 2025-01-09 13:33:51 +01:00
drivers net: ethernet: ti: am65-cpsw: default to round-robin for host port receive 2025-01-09 13:33:52 +01:00
fs ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv 2025-01-09 13:33:49 +01:00
include RDMA/mlx5: Enable multiplane mode only when it is supported 2025-01-09 13:33:48 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring/rw: fix downgraded mshot read 2025-01-09 13:33:51 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel fgraph: Add READ_ONCE() when accessing fgraph_array[] 2025-01-09 13:33:52 +01:00
lib maple_tree: reload mas before the second call for mas_empty_area 2025-01-09 13:33:50 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: convert partially_mapped set/clear operations to be atomic 2024-12-27 14:02:20 +01:00
net net/sctp: Prevent autoclose integer overflow in sctp_association_init() 2025-01-09 13:33:51 +01:00
rust rust: kbuild: set bindgen's Rust target version 2024-12-19 18:13:22 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:03:46 +01:00
scripts scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity 2025-01-09 13:33:50 +01:00
security selinux: ignore unknown extended permissions 2025-01-09 13:33:32 +01:00
sound ALSA: seq: oss: Fix races at processing SysEx messages 2025-01-09 13:33:49 +01:00
tools bpf: consider that tail calls invalidate packet pointers 2025-01-09 13:33:47 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.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 Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.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 mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -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 MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile Linux 6.12.8 2025-01-02 10:34:26 +01:00
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.