[PATCH stable 4.19] net: phy: broadcom: stub c45 read/write for 54810

[Florian Fainelli]

From: Justin Chen <justin.chen@xxxxxxxxxxxx>

commit 096516d092d54604d590827d05b1022c8f326639 upstream

The 54810 does not support c45. The mmd_phy_indirect accesses return
arbirtary values leading to odd behavior like saying it supports EEE
when it doesn't. We also see that reading/writing these non-existent
MMD registers leads to phy instability in some cases.

Fixes: b14995ac2527 ("net: phy: broadcom: Add BCM54810 PHY entry")
Signed-off-by: Justin Chen <justin.chen@xxxxxxxxxxxx>
Reviewed-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1691901708-28650-1-git-send-email-justin.chen@xxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
[florian: resolved conflicts in 4.19]
Signed-off-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
---
 drivers/net/phy/broadcom.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
index 94622d119abc..49fb62d02a76 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c
@@ -421,6 +421,17 @@ static int bcm5482_read_status(struct phy_device *phydev)
 	return err;
 }
 
+static int bcm54810_read_mmd(struct phy_device *phydev, int devnum, u16 regnum)
+{
+	return -EOPNOTSUPP;
+}
+
+static int bcm54810_write_mmd(struct phy_device *phydev, int devnum, u16 regnum,
+			      u16 val)
+{
+	return -EOPNOTSUPP;
+}
+
 static int bcm5481_config_aneg(struct phy_device *phydev)
 {
 	struct device_node *np = phydev->mdio.dev.of_node;
@@ -684,6 +695,8 @@ static struct phy_driver broadcom_drivers[] = {
 	.name           = "Broadcom BCM54810",
 	.features       = PHY_GBIT_FEATURES,
 	.flags          = PHY_HAS_INTERRUPT,
+	.read_mmd	= bcm54810_read_mmd,
+	.write_mmd	= bcm54810_write_mmd,
 	.config_init    = bcm54xx_config_init,
 	.config_aneg    = bcm5481_config_aneg,
 	.ack_interrupt  = bcm_phy_ack_intr,
-- 
2.34.1

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