[PATCH net 4/6] net: dsa: vsc73xx: check busy flag in MDIO operations

[Pawel Dembicki <paweldembicki@gmail.com>]

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.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>

---
This patch came from net-next series[0].
Changes since net-next:
  - removed mutex
  - used method poll.h to poll busy value in 'vsc73xx_mdio_busy_check'
  - use 'vsc73xx_mdio_busy_check' for control if mdio is ready

[0] https://patchwork.kernel.org/project/netdevbpf/patch/20240729210615.279952-6-paweldembicki@gmail.com/
---
 drivers/net/dsa/vitesse-vsc73xx-core.c | 33 ++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index b6c46a3da9a5..42b4f312c418 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -317,6 +317,7 @@
 #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 {
@@ -545,6 +546,22 @@ 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;
@@ -552,6 +569,10 @@ 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 = VSC73XX_MII_CMD_OPERATION |
 	      FIELD_PREP(VSC73XX_MII_CMD_PHY_ADDR, phy) |
@@ -560,7 +581,11 @@ static int vsc73xx_phy_read(struct dsa_switch *ds, int phy, int regnum)
 			    VSC73XX_MII_CMD, cmd);
 	if (ret)
 		return ret;
-	msleep(2);
+
+	ret = vsc73xx_mdio_busy_check(vsc);
+	if (ret)
+		return ret;
+
 	ret = vsc73xx_read(vsc, VSC73XX_BLOCK_MII, VSC73XX_BLOCK_MII_INTERNAL,
 			   VSC73XX_MII_DATA, &val);
 	if (ret)
@@ -583,7 +608,11 @@ static int vsc73xx_phy_write(struct dsa_switch *ds, int phy, int regnum,
 {
 	struct vsc73xx *vsc = ds->priv;
 	u32 cmd;
-	int ret;
+	int ret = 0;
+
+	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
-- 
2.34.1