Patch "net: dsa: vsc73xx: check busy flag in MDIO operations" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    net: dsa: vsc73xx: check busy flag in MDIO operations

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-dsa-vsc73xx-check-busy-flag-in-mdio-operations.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e56af52cd7ff5da5564528ab8763adf461e95951
Author: Pawel Dembicki <paweldembicki@xxxxxxxxx>
Date:   Fri Aug 9 21:38:04 2024 +0200

    net: dsa: vsc73xx: check busy flag in MDIO operations
    
    [ Upstream commit fa63c6434b6f6aaf9d8d599dc899bc0a074cc0ad ]
    
    The VSC73xx has a busy flag used during MDIO operations. It is raised
    when MDIO read/write operations are in progress. Without it, PHYs are
    misconfigured and bus operations do not work as expected.
    
    Fixes: 05bd97fc559d ("net: dsa: Add Vitesse VSC73xx DSA router driver")
    Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
    Reviewed-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
    Signed-off-by: Pawel Dembicki <paweldembicki@xxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index 92087f9d73550..c8e9ca5d5c284 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -39,6 +39,10 @@
 #define VSC73XX_BLOCK_ARBITER	0x5 /* Only subblock 0 */
 #define VSC73XX_BLOCK_SYSTEM	0x7 /* Only subblock 0 */
 
+/* MII Block subblock */
+#define VSC73XX_BLOCK_MII_INTERNAL	0x0 /* Internal MDIO subblock */
+#define VSC73XX_BLOCK_MII_EXTERNAL	0x1 /* External MDIO subblock */
+
 #define CPU_PORT	6 /* CPU port */
 
 /* MAC Block registers */
@@ -197,6 +201,8 @@
 #define VSC73XX_MII_CMD		0x1
 #define VSC73XX_MII_DATA	0x2
 
+#define VSC73XX_MII_STAT_BUSY	BIT(3)
+
 /* Arbiter block 5 registers */
 #define VSC73XX_ARBEMPTY		0x0c
 #define VSC73XX_ARBDISC			0x0e
@@ -271,6 +277,7 @@
 #define IS_739X(a) (IS_7395(a) || IS_7398(a))
 
 #define VSC73XX_POLL_SLEEP_US		1000
+#define VSC73XX_MDIO_POLL_SLEEP_US	5
 #define VSC73XX_POLL_TIMEOUT_US		10000
 
 struct vsc73xx_counter {
@@ -488,6 +495,22 @@ static int vsc73xx_detect(struct vsc73xx *vsc)
 	return 0;
 }
 
+static int vsc73xx_mdio_busy_check(struct vsc73xx *vsc)
+{
+	int ret, err;
+	u32 val;
+
+	ret = read_poll_timeout(vsc73xx_read, err,
+				err < 0 || !(val & VSC73XX_MII_STAT_BUSY),
+				VSC73XX_MDIO_POLL_SLEEP_US,
+				VSC73XX_POLL_TIMEOUT_US, false, vsc,
+				VSC73XX_BLOCK_MII, VSC73XX_BLOCK_MII_INTERNAL,
+				VSC73XX_MII_STAT, &val);
+	if (ret)
+		return ret;
+	return err;
+}
+
 static int vsc73xx_phy_read(struct dsa_switch *ds, int phy, int regnum)
 {
 	struct vsc73xx *vsc = ds->priv;
@@ -495,12 +518,20 @@ static int vsc73xx_phy_read(struct dsa_switch *ds, int phy, int regnum)
 	u32 val;
 	int ret;
 
+	ret = vsc73xx_mdio_busy_check(vsc);
+	if (ret)
+		return ret;
+
 	/* Setting bit 26 means "read" */
 	cmd = BIT(26) | (phy << 21) | (regnum << 16);
 	ret = vsc73xx_write(vsc, VSC73XX_BLOCK_MII, 0, 1, cmd);
 	if (ret)
 		return ret;
-	msleep(2);
+
+	ret = vsc73xx_mdio_busy_check(vsc);
+	if (ret)
+		return ret;
+
 	ret = vsc73xx_read(vsc, VSC73XX_BLOCK_MII, 0, 2, &val);
 	if (ret)
 		return ret;
@@ -524,6 +555,10 @@ static int vsc73xx_phy_write(struct dsa_switch *ds, int phy, int regnum,
 	u32 cmd;
 	int ret;
 
+	ret = vsc73xx_mdio_busy_check(vsc);
+	if (ret)
+		return ret;
+
 	/* It was found through tedious experiments that this router
 	 * chip really hates to have it's PHYs reset. They
 	 * never recover if that happens: autonegotiation stops




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