netdev - [PATCH RFC 7/7] net: phy: read MMD ID from all present MMDs

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Date:   Tue, 26 May 2020 15:31:32 +0100
From:   Russell King <rmk+kernel@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Cc:     Jeremy Linton <jeremy.linton@....com>,
        Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: [PATCH RFC 7/7] net: phy: read MMD ID from all present MMDs

Expand the device_ids[] array to allow all MMD IDs to be read rather
than just the first 8 MMDs, but only read the ID if the MDIO_STAT2
register reports that a device really is present here for these new
devices to maintain compatibility with our current behaviour.

88X3310 PHY vendor MMDs do are marked as present in the
devices_in_package, but do not contain IEE 802.3 compatible register
sets in their lower space.  This avoids reading incorrect values as MMD
identifiers.

Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
---
 drivers/net/phy/phy_device.c | 14 ++++++++++++++
 include/linux/phy.h          |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 1c948bbf4fa0..92742c7be80f 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -773,6 +773,20 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
 		if (!(devs_in_pkg & (1 << i)))
 			continue;
 
+		if (i >= 8) {
+			/* Only probe the MMD ID for MMDs >= 8 if they report
+			 * that they are present. We have at least one PHY that
+			 * reports MMD presence in devs_in_pkg, but does not
+			 * contain valid IEEE 802.3 ID registers in some MMDs.
+			 */
+			ret = phy_c45_probe_present(bus, addr, i);
+			if (ret < 0)
+				return ret;
+
+			if (!ret)
+				continue;
+		}
+
 		phy_reg = mdiobus_c45_read(bus, addr, i, MII_PHYSID1);
 		if (phy_reg < 0)
 			return -EIO;
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 0d41c710339a..3325dd8fb9ac 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -361,7 +361,7 @@ enum phy_state {
 struct phy_c45_device_ids {
 	u32 devices_in_package;
 	u32 mmds_present;
-	u32 device_ids[8];
+	u32 device_ids[MDIO_MMD_NUM];
 };
 
 struct macsec_context;
-- 
2.20.1