netdev - [PATCH] net: phy: return EPROBE_DEFER if PHY is not accessible

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Date:   Fri, 17 Mar 2023 13:16:46 +0100
From:   <arturo.buzarra@...i.com>
To:     <netdev@...r.kernel.org>
Subject: [PATCH] net: phy: return EPROBE_DEFER if PHY is not accessible

From: Arturo Buzarra <arturo.buzarra@...i.com>

A PHY driver can dynamically determine the devices features, but in some
circunstances, the PHY is not yet ready and the read capabilities does not fail
but returns an undefined value, so incorrect capabilities are assumed and the
initialization process fails. This commit postpones the PHY probe to ensure the
PHY is accessible.

Signed-off-by: Arturo Buzarra <arturo.buzarra@...i.com>
---
 drivers/net/phy/phy_device.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 1785f1cead97..f8c31e741936 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2628,10 +2628,14 @@ int genphy_read_abilities(struct phy_device *phydev)
 			       phydev->supported);
 
 	val = phy_read(phydev, MII_BMSR);
 	if (val < 0)
 		return val;
+	if (val == 0x0000 || val == 0xffff) {
+		phydev_err(phydev, "PHY is not accessible\n");
+		return -EPROBE_DEFER;
+	}
 
 	linkmode_mod_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, phydev->supported,
 			 val & BMSR_ANEGCAPABLE);
 
 	linkmode_mod_bit(ETHTOOL_LINK_MODE_100baseT_Full_BIT, phydev->supported,