Re: [RFC net-next v3 3/3] net: dsa: microchip: implement PHY loopback configuration for KSZ8794 and KSZ8873

On Fri, Jan 12, 2024 at 03:07:16PM +0100, Oleksij Rempel wrote:

Correct the PHY loopback bit handling in the ksz8_w_phy_bmcr and
ksz8_r_phy_bmcr functions for KSZ8794 and KSZ8873 variants in the ksz8795
driver. Previously, the code erroneously used Bit 7 of port register 0xD
for both chip variants, which is actually for LED configuration. This
update ensures the correct registers and bits are used for the PHY
loopback feature:

- For KSZ8794: Use 0xF / Bit 7.
- For KSZ8873: Use 0xD / Bit 0.

The lack of loopback support was seen on KSZ8873 system by using
"ethtool -t lanX". After this patch, the ethtool selftest will work,
but only if port is not part of a bridge.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
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Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>