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Marek Behún 526c8ee04b net: dsa: qca8k: fix potential MDIO bus conflict when accessing internal PHYs via management frames 
Besides the QCA8337 switch the Turris 1.x device has on it's MDIO bus
also Micron ethernet PHY (dedicated to the WAN port).

We've been experiencing a strange behavior of the WAN ethernet
interface, wherein the WAN PHY started timing out the MDIO accesses, for
example when the interface was brought down and then back up.

Bisecting led to commit 2cd5485663 ("net: dsa: qca8k: add support for
phy read/write with mgmt Ethernet"), which added support to access the
QCA8337 switch's internal PHYs via management ethernet frames.

Connecting the MDIO bus pins onto an oscilloscope, I was able to see
that the MDIO bus was active whenever a request to read/write an
internal PHY register was done via an management ethernet frame.

My theory is that when the switch core always communicates with the
internal PHYs via the MDIO bus, even when externally we request the
access via ethernet. This MDIO bus is the same one via which the switch
and internal PHYs are accessible to the board, and the board may have
other devices connected on this bus. An ASCII illustration may give more
insight:

           +---------+
      +----|         |
      |    | WAN PHY |
      | +--|         |
      | |  +---------+
      | |
      | |  +----------------------------------+
      | |  | QCA8337                          |
MDC   | |  |                        +-------+ |
------o-+--|--------o------------o--|       | |
MDIO    |  |        |            |  | PHY 1 |-|--to RJ45
--------o--|---o----+---------o--+--|       | |
           |   |    |         |  |  +-------+ |
	   | +-------------+  |  o--|       | |
	   | | MDIO MDC    |  |  |  | PHY 2 |-|--to RJ45
eth1	   | |             |  o--+--|       | |
-----------|-|port0        |  |  |  +-------+ |
           | |             |  |  o--|       | |
	   | | switch core |  |  |  | PHY 3 |-|--to RJ45
           | +-------------+  o--+--|       | |
	   |                  |  |  +-------+ |
	   |                  |  o--|  ...  | |
	   +----------------------------------+

When we send a request to read an internal PHY register via an ethernet
management frame via eth1, the switch core receives the ethernet frame
on port 0 and then communicates with the internal PHY via MDIO. At this
time, other potential devices, such as the WAN PHY on Turris 1.x, cannot
use the MDIO bus, since it may cause a bus conflict.

Fix this issue by locking the MDIO bus even when we are accessing the
PHY registers via ethernet management frames.

Fixes: 2cd5485663 ("net: dsa: qca8k: add support for phy read/write with mgmt Ethernet")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-10-06 11:41:52 +01:00
arch Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
block block: fix kernel-doc for disk_force_media_change() 2023-09-26 00:43:34 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: sm2 - Fix crash caused by uninitialized context 2023-09-20 13:10:10 +08:00
Documentation Couple of small fixes, including: 2023-10-05 11:03:20 -07:00
drivers net: dsa: qca8k: fix potential MDIO bus conflict when accessing internal PHYs via management frames 2023-10-06 11:41:52 +01:00
fs overlayfs fixes for 6.6-rc5 2023-10-05 10:56:18 -07:00
include Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring io_uring/fs: remove sqe->rw_flags checking from LINKAT 2023-09-29 03:07:09 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
lib maple_tree: add MAS_UNDERFLOW and MAS_OVERFLOW states 2023-09-29 17:20:46 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Fourteen hotfixes, eleven of which are cc:stable. The remainder pertain 2023-10-01 13:33:25 -07:00
net Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts kbuild: remove stale code for 'source' symlink in packaging scripts 2023-10-01 23:06:06 +09:00
security ima: rework CONFIG_IMA dependency block 2023-09-27 11:52:12 -04:00
sound ASoC: Fixes for v6.6 2023-09-20 15:02:16 +02:00
tools Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap MAINTAINERS: update Matthieu's email address 2023-10-05 09:34:32 -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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 Including fixes from Bluetooth, netfilter, BPF and WiFi. 2023-10-05 11:29:21 -07:00
Makefile Linux 6.6-rc4 2023-10-01 14:15:13 -07:00
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.