[PATCH net v2 3/5] net: dsa: mt7530: error out on failed reads in ATC/VTCR command polling

[Daniel Golle <daniel@makrotopia.org>]

mt7530_fdb_cmd() and mt7530_vlan_cmd() poll the command register
through a helper which returns 0 when the underlying read fails. A
failed bus transaction thus clears ATC_BUSY/VTCR_BUSY and is treated
as successful command completion, and the subsequent ATC_INVALID and
VTCR_INVALID checks are defeated the same way.

Poll using regmap_read_poll_timeout(), which stops on read errors and
propagates them, and use the register value it already read back
instead of re-reading it. Take the MDIO bus lock across the sequence
as the switch regmap is set up with locking disabled.

Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Fixes: 83163f7dca56 ("net: dsa: mediatek: add VLAN support for MT7530")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
v2:
 * drop the extra regmap_read() after regmap_read_poll_timeout(); the
   macro already leaves the polled value in val (found by Sashiko AI
   review)
 * print ret in the error messages and stop mislabeling propagated bus
   errors as "reset timeout"/"poll timeout"

 drivers/net/dsa/mt7530.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index f349b54c2d9e..aab26970f39b 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -252,24 +252,26 @@ mt7530_fdb_cmd(struct mt7530_priv *priv, enum mt7530_fdb_cmd cmd, u32 *rsp)
 {
 	u32 val;
 	int ret;
-	struct mt7530_dummy_poll p;
 
 	/* Set the command operating upon the MAC address entries */
 	val = ATC_BUSY | ATC_MAT(0) | cmd;
 	mt7530_write(priv, MT7530_ATC, val);
 
-	INIT_MT7530_DUMMY_POLL(&p, priv, MT7530_ATC);
-	ret = readx_poll_timeout(_mt7530_read, &p, val,
-				 !(val & ATC_BUSY), 20, 20000);
+	mt7530_mutex_lock(priv);
+
+	ret = regmap_read_poll_timeout(priv->regmap, MT7530_ATC, val,
+				       !(val & ATC_BUSY), 20, 20000);
+
+	mt7530_mutex_unlock(priv);
+
 	if (ret < 0) {
-		dev_err(priv->dev, "reset timeout\n");
+		dev_err(priv->dev, "ATC poll failed: %d\n", ret);
 		return ret;
 	}
 
 	/* Additional sanity for read command if the specified
 	 * entry is invalid
 	 */
-	val = mt7530_read(priv, MT7530_ATC);
 	if ((cmd == MT7530_FDB_READ) && (val & ATC_INVALID))
 		return -EINVAL;
 
@@ -1630,22 +1632,24 @@ mt7530_port_bridge_join(struct dsa_switch *ds, int port,
 static int
 mt7530_vlan_cmd(struct mt7530_priv *priv, enum mt7530_vlan_cmd cmd, u16 vid)
 {
-	struct mt7530_dummy_poll p;
 	u32 val;
 	int ret;
 
 	val = VTCR_BUSY | VTCR_FUNC(cmd) | vid;
 	mt7530_write(priv, MT7530_VTCR, val);
 
-	INIT_MT7530_DUMMY_POLL(&p, priv, MT7530_VTCR);
-	ret = readx_poll_timeout(_mt7530_read, &p, val,
-				 !(val & VTCR_BUSY), 20, 20000);
+	mt7530_mutex_lock(priv);
+
+	ret = regmap_read_poll_timeout(priv->regmap, MT7530_VTCR, val,
+				       !(val & VTCR_BUSY), 20, 20000);
+
+	mt7530_mutex_unlock(priv);
+
 	if (ret < 0) {
-		dev_err(priv->dev, "poll timeout\n");
+		dev_err(priv->dev, "VTCR poll failed: %d\n", ret);
 		return ret;
 	}
 
-	val = mt7530_read(priv, MT7530_VTCR);
 	if (val & VTCR_INVALID) {
 		dev_err(priv->dev, "read VTCR invalid\n");
 		return -EINVAL;
-- 
2.55.0