[PATCH net-next v4 1/3] net: phy: realtek: use C45 for RTL8365MB-VC internal PHY MMD access

The RTL8365MB-VC PHYs are integrated into the switch and have no MMD
registers of their own. What phylib would access as MMD registers (the EEE
ability/advertisement) lives in the switch's OCP registers instead.

For a C22 PHY, phy_read_mmd()/phy_write_mmd() use C22 indirect-MMD, which
this hardware does not implement. Point .read_mmd/.write_mmd at
genphy_{read,write}_mmd_c45() so phylib issues those MMD accesses over C45,
where the DSA user MDIO bus can carry them to the switch's OCP registers.

This patch only redirects the MMD access path; it does not enable EEE. The
OCP mapping (the DSA bus .read_c45/.write_c45 handlers) and EEE support are
added by the following patch. Until then an MMD access returns -EOPNOTSUPP;
the only one that runs is the EEE-ability read in phy_probe(), which phylib
ignores, so probe, link and traffic are unaffected and ethtool --show-eee
reports EEE unsupported -- the same as before this series, not a regression
(verified on an RTL8365MB-VC).

Signed-off-by: Oleksij Rempel <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Reviewed-by: Luiz Angelo Daros de Luca <[email protected]>
---
Changes since v3:
- Commit message only: state in the body that this patch only redirects the
  MMD path and does not enable EEE (that is added by the following patch),
  folding the prerequisite / no-regression note from the anticipated-questions
  section into the body; no code change.
---
 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 97b0b67b9900..b55691681df6 100644
--- a/drivers/net/phy/realtek/realtek_main.c
+++ b/drivers/net/phy/realtek/realtek_main.c
@@ -3338,6 +3338,8 @@ 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