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@broadcom.com>
---
v2
	- Change EINVAL to EOPNOTSUPP
 
 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 59cae0d808aa..04b2e6eeb195 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c
@@ -542,6 +542,17 @@ static int bcm54xx_resume(struct phy_device *phydev)
 	return bcm54xx_config_init(phydev);
 }
 
+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 bcm54811_config_init(struct phy_device *phydev)
 {
 	int err, reg;
@@ -1103,6 +1114,8 @@ static struct phy_driver broadcom_drivers[] = {
 	.get_strings	= bcm_phy_get_strings,
 	.get_stats	= bcm54xx_get_stats,
 	.probe		= bcm54xx_phy_probe,
+	.read_mmd	= bcm54810_read_mmd,
+	.write_mmd	= bcm54810_write_mmd,
 	.config_init    = bcm54xx_config_init,
 	.config_aneg    = bcm5481_config_aneg,
 	.config_intr    = bcm_phy_config_intr,
-- 
2.7.4

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sat, 12 Aug 2023 21:41:47 -0700 you wrote:
> 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@broadcom.com>
> 
> [...]

Here is the summary with links:
  - [net,v2] net: phy: broadcom: stub c45 read/write for 54810
    https://git.kernel.org/netdev/net/c/096516d092d5

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On 8/12/2023 9:41 PM, Justin Chen wrote:
> 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@broadcom.com>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian