[PATCH net-next v2 1/2] net: phy: realtek: use C45 for RTL8365MB-VC internal PHY MMD access

[Oleksij Rempel]

The RTL8365MB-VC PHYs are integrated into the switch and have no MMD
registers of their own. What phylib accesses as MMD registers (EEE)
actually lives in the switch's OCP registers; the realtek DSA driver maps
those MMD requests onto OCP and exposes them over C45.

For a C22 PHY, phy_read_mmd()/phy_write_mmd() would use C22 indirect-MMD,
which this hardware does not implement. Point .read_mmd/.write_mmd at
genphy_{read,write}_mmd_c45() so phylib's MMD accesses go over C45 to the
DSA driver's mapping instead.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
---
Anticipated reviewer questions:

Q: .read_mmd/.write_mmd now use the C45 helpers, but the DSA user MDIO bus
   only gains .read_c45/.write_c45 in the next patch -- is this bisect-broken?
A: No. Until then an MMD access returns -EOPNOTSUPP, but the only one that runs
   is the EEE-ability read in phy_probe(), which phylib ignores; probe, link and
   traffic are unaffected. ethtool --show-eee reports EEE unsupported here -- the
   same as before this series, since these ports gain EEE only in the next patch
   -- so it is not a regression. Verified on an RTL8365MB-VC.
---
 drivers/net/phy/realtek/realtek_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/phy/realtek/realtek_main.c b/drivers/net/phy/realtek/realtek_main.c
index 177b62a7b2d1..ad8017e91b4f 100644
--- a/drivers/net/phy/realtek/realtek_main.c
+++ b/drivers/net/phy/realtek/realtek_main.c
@@ -3388,6 +3388,8 @@ static struct phy_driver realtek_drvs[] = {
 	}, {
 		PHY_ID_MATCH_EXACT(0x001cc942),
 		.name		= "RTL8365MB-VC Gigabit Ethernet",
+		.read_mmd	= genphy_read_mmd_c45,
+		.write_mmd	= genphy_write_mmd_c45,
 		/* Interrupt handling analogous to RTL8366RB */
 		.config_intr	= genphy_no_config_intr,
 		.handle_interrupt = genphy_handle_interrupt_no_ack,
-- 
2.47.3