linux-kernel - [PATCH RFC net-next 0/5] net: phy: C45-over-C22 access

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Message-Id: <20220323183419.2278676-1-michael@walle.cc>
Date:   Wed, 23 Mar 2022 19:34:14 +0100
From:   Michael Walle <michael@...le.cc>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Xu Liang <lxu@...linear.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Walle <michael@...le.cc>
Subject: [PATCH RFC net-next 0/5] net: phy: C45-over-C22 access

Hi,

This is the result of this discussion:
https://lore.kernel.org/netdev/240354b0a54b37e8b5764773711b8aa3@walle.cc/

The goal here is to get the GYP215 and LAN8814 running on the Microchip
LAN9668 SoC. The LAN9668 suppports one external bus and unfortunately, the
LAN8814 has a bug which makes it impossible to use C45 on that bus.
Fortunately, it was the intention of the GPY215 driver to be used on a C22
bus. But I think this could have never really worked, because the
phy_get_c45_ids() will always do c45 accesses and thus on MDIO bus drivers
which will correctly check for the MII_ADDR_C45 flag and return -EOPNOTSUPP
the function call will fail and thus gpy_probe() will fail. This series
tries to fix that and will lay the foundation to add a workaround for the
LAN8814 bug by forcing an MDIO bus to be c22-only.

At the moment, the probe_capabilities is taken into account to decide if
we have to use C45-over-C22. What is still missing from this series is the
handling of a device tree property to restrict the probe_capabilities to
c22-only.

Since net-next is closed, this is marked as RFC to get some early feedback.

Michael Walle (5):
  net: phy: mscc-miim: reject clause 45 register accesses
  net: phy: support indirect c45 access in get_phy_c45_ids()
  net: phy: mscc-miim: add probe_capabilities
  net: phy: introduce is_c45_over_c22 flag
  net: phylink: handle the new is_c45_over_c22 property

 drivers/net/mdio/mdio-mscc-miim.c |  7 ++++
 drivers/net/phy/mxl-gpy.c         |  2 +-
 drivers/net/phy/phy_device.c      | 65 ++++++++++++++++++++++++++-----
 drivers/net/phy/phylink.c         |  2 +-
 include/linux/phy.h               |  4 +-
 5 files changed, 68 insertions(+), 12 deletions(-)

-- 
2.30.2