netdev - [PATCH v3 net-next 06/13] net: pcs: xpcs: also ignore phy id if it's all ones

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Message-Id: <20210611200531.2384819-7-olteanv@gmail.com>
Date:   Fri, 11 Jun 2021 23:05:24 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Wong Vee Khee <vee.khee.wong@...ux.intel.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: [PATCH v3 net-next 06/13] net: pcs: xpcs: also ignore phy id if it's all ones

From: Vladimir Oltean <vladimir.oltean@....com>

xpcs_get_id() searches multiple MMDs for a known PHY ID, starting with
MDIO_MMD_PCS (3). However not all integrators might have implemented
that MMD on their MDIO bus. For example, the NXP SJA1105 and SJA1110
switches only implement vendor-specific MMD 1 and 2.

When there is nothing on an MDIO bus at a certain address, traditionally
the bus returns 0xffff, which means that the bus remained in its default
pull-up state for the duration of the MDIO transaction. The 0xffff value
is widely used in drivers/net/phy/phy_device.c (see get_phy_c22_id for
example) to denote a missing device.

So it makes sense for the xpcs to ignore this value as well, and
continue its search, eventually finding the proper PHY ID in the
vendor-specific MMDs.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
v2->v3: none
v1->v2: none

 drivers/net/pcs/pcs-xpcs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 743b53734eeb..ecf5011977d3 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -965,8 +965,10 @@ static u32 xpcs_get_id(struct dw_xpcs *xpcs)
 	if (ret < 0)
 		return 0xffffffff;
 
-	/* If Device IDs are not all zeros, we found C73 AN-type device */
-	if (id | ret)
+	/* If Device IDs are not all zeros or all ones,
+	 * we found C73 AN-type device
+	 */
+	if ((id | ret) && (id | ret) != 0xffffffff)
 		return id | ret;
 
 	/* Next, search C37 PCS using Vendor-Specific MII MMD */
-- 
2.25.1