linux-kernel - [PATCH net-next v2 01/10] net: phy: add error checks in mmd_phy

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Message-Id: <20230620-feature-c45-over-c22-v2-1-def0ab9ccee2@kernel.org>
Date:   Fri, 23 Jun 2023 12:29:10 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Marek Behún <kabel@...nel.org>,
        Xu Liang <lxu@...linear.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Walle <mwalle@...nel.org>
Subject: [PATCH net-next v2 01/10] net: phy: add error checks in
 mmd_phy_indirect() and export it

Add missing error checks in mmd_phy_indirect(). The error checks need to
be disabled to retain the current behavior in phy_read_mmd() and
phy_write_mmd(). Therefore, add a new parameter to enable the error
checks. Add a thin wrapper __phy_mmd_indirect() which is then exported.

Regarding the legacy handling, Russell states:

| The reason for that goes back to commit a59a4d192166 ("phy: add the
| EEE support and the way to access to the MMD registers.")
|
| and to maintain compatibility with that; if we start checking for
| errors now, we might trigger a kernel regression sadly.

Signed-off-by: Michael Walle <mwalle@...nel.org>
---
 drivers/net/phy/phy-core.c | 42 ++++++++++++++++++++++++++++++++++--------
 include/linux/phy.h        |  2 ++
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index a64186dc53f8..65ff58b36fc0 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -524,19 +524,45 @@ int phy_speed_down_core(struct phy_device *phydev)
 	return 0;
 }
 
-static void mmd_phy_indirect(struct mii_bus *bus, int phy_addr, int devad,
-			     u16 regnum)
+static int mmd_phy_indirect(struct mii_bus *bus, int phy_addr, int devad,
+			    u16 regnum, bool check_rc)
 {
+	int ret;
+
 	/* Write the desired MMD Devad */
-	__mdiobus_write(bus, phy_addr, MII_MMD_CTRL, devad);
+	ret = __mdiobus_write(bus, phy_addr, MII_MMD_CTRL, devad);
+	if (check_rc && ret)
+		return ret;
 
 	/* Write the desired MMD register address */
-	__mdiobus_write(bus, phy_addr, MII_MMD_DATA, regnum);
+	ret = __mdiobus_write(bus, phy_addr, MII_MMD_DATA, regnum);
+	if (check_rc && ret)
+		return ret;
 
 	/* Select the Function : DATA with no post increment */
-	__mdiobus_write(bus, phy_addr, MII_MMD_CTRL,
-			devad | MII_MMD_CTRL_NOINCR);
+	ret = __mdiobus_write(bus, phy_addr, MII_MMD_CTRL,
+			      devad | MII_MMD_CTRL_NOINCR);
+
+	return check_rc ? ret : 0;
+}
+
+/**
+ * __phy_mmd_indirect - prepare an indirect C45 register access
+ *
+ * @bus: the target MII bus
+ * @phy_addr: PHY address on the MII bus
+ * @devad: The target MMD (0..31)
+ * @regnum: The target register on the MMD (0..65535)
+ *
+ * Prepare an indirect C45 read or write transfer using the MII_MMD_CTRL and
+ * MII_MMD_DATA registers in C22 space.
+ */
+int __phy_mmd_indirect(struct mii_bus *bus, int phy_addr, int devad,
+		       u16 regnum)
+{
+	return mmd_phy_indirect(bus, phy_addr, devad, regnum, true);
 }
+EXPORT_SYMBOL(__phy_mmd_indirect);
 
 /**
  * __phy_read_mmd - Convenience function for reading a register
@@ -563,7 +589,7 @@ int __phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum)
 		struct mii_bus *bus = phydev->mdio.bus;
 		int phy_addr = phydev->mdio.addr;
 
-		mmd_phy_indirect(bus, phy_addr, devad, regnum);
+		mmd_phy_indirect(bus, phy_addr, devad, regnum, false);
 
 		/* Read the content of the MMD's selected register */
 		val = __mdiobus_read(bus, phy_addr, MII_MMD_DATA);
@@ -619,7 +645,7 @@ int __phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val)
 		struct mii_bus *bus = phydev->mdio.bus;
 		int phy_addr = phydev->mdio.addr;
 
-		mmd_phy_indirect(bus, phy_addr, devad, regnum);
+		mmd_phy_indirect(bus, phy_addr, devad, regnum, false);
 
 		/* Write the data into MMD's selected register */
 		__mdiobus_write(bus, phy_addr, MII_MMD_DATA, val);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 11c1e91563d4..9521b815d3f0 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1316,6 +1316,8 @@ int phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum);
 	__ret; \
 })
 
+int __phy_mmd_indirect(struct mii_bus *bus, int phy_addr, int devad,
+		       u16 regnum);
 /*
  * __phy_read_mmd - Convenience function for reading a register
  * from an MMD on a given PHY.

-- 
2.39.2