[RFC PATCH net-next v4 21/28] net: dsa: qca8k: dsa: qca8k: protect MASTER busy_wait with mdio mutex

[Ansuel Smith]

MDIO_MASTER operation have a dedicated busy wait that is not protected
by the mdio mutex. This can cause situation where the MASTER operation
is done and a normal operation is executed between the MASTER read/write
and the MASTER busy_wait. Rework the qca8k_mdio_read/write function to
address this issue by binding the lock for the whole MASTER operation
and not only the mdio read/write common operation.

Signed-off-by: Ansuel Smith <ansuelsmth@xxxxxxxxx>
---
 drivers/net/dsa/qca8k.c | 68 +++++++++++++++++++++++++++++++++--------
 1 file changed, 55 insertions(+), 13 deletions(-)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index 2e0d2f918efe..e272ccaaa7f6 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -639,9 +639,32 @@ qca8k_port_to_phy(int port)
 	return port - 1;
 }
 
+static int
+qca8k_mdio_busy_wait(struct qca8k_priv *priv, u32 reg, u32 mask)
+{
+	u16 r1, r2, page;
+	u32 val;
+	int ret;
+
+	qca8k_split_addr(reg, &r1, &r2, &page);
+
+	ret = read_poll_timeout(qca8k_mii_read32, val, !(val & mask), 0,
+				QCA8K_BUSY_WAIT_TIMEOUT * USEC_PER_MSEC, false,
+				priv->bus, 0x10 | r2, r1);
+
+	/* Check if qca8k_read has failed for a different reason
+	 * before returnting -ETIMEDOUT
+	 */
+	if (ret < 0 && val < 0)
+		return val;
+
+	return ret;
+}
+
 static int
 qca8k_mdio_write(struct qca8k_priv *priv, int port, u32 regnum, u16 data)
 {
+	u16 r1, r2, page;
 	u32 phy, val;
 	int ret;
 
@@ -657,12 +680,21 @@ qca8k_mdio_write(struct qca8k_priv *priv, int port, u32 regnum, u16 data)
 	      QCA8K_MDIO_MASTER_REG_ADDR(regnum) |
 	      QCA8K_MDIO_MASTER_DATA(data);
 
-	ret = qca8k_write(priv, QCA8K_MDIO_MASTER_CTRL, val);
+	qca8k_split_addr(QCA8K_MDIO_MASTER_CTRL, &r1, &r2, &page);
+
+	mutex_lock_nested(&priv->bus->mdio_lock, MDIO_MUTEX_NESTED);
+
+	ret = qca8k_set_page(priv->bus, page);
 	if (ret)
-		return ret;
+		goto exit;
+
+	qca8k_mii_write32(priv->bus, 0x10 | r2, r1, val);
+
+	ret = qca8k_mdio_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
+				   QCA8K_MDIO_MASTER_BUSY);
 
-	ret = qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
-			      QCA8K_MDIO_MASTER_BUSY);
+exit:
+	mutex_unlock(&priv->bus->mdio_lock);
 
 	/* even if the busy_wait timeouts try to clear the MASTER_EN */
 	qca8k_reg_clear(priv, QCA8K_MDIO_MASTER_CTRL,
@@ -674,6 +706,7 @@ qca8k_mdio_write(struct qca8k_priv *priv, int port, u32 regnum, u16 data)
 static int
 qca8k_mdio_read(struct qca8k_priv *priv, int port, u32 regnum)
 {
+	u16 r1, r2, page;
 	u32 phy, val;
 	int ret;
 
@@ -688,21 +721,30 @@ qca8k_mdio_read(struct qca8k_priv *priv, int port, u32 regnum)
 	      QCA8K_MDIO_MASTER_READ | QCA8K_MDIO_MASTER_PHY_ADDR(phy) |
 	      QCA8K_MDIO_MASTER_REG_ADDR(regnum);
 
-	ret = qca8k_write(priv, QCA8K_MDIO_MASTER_CTRL, val);
-	if (ret)
-		return ret;
+	qca8k_split_addr(QCA8K_MDIO_MASTER_CTRL, &r1, &r2, &page);
+
+	mutex_lock_nested(&priv->bus->mdio_lock, MDIO_MUTEX_NESTED);
 
-	ret = qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
-			      QCA8K_MDIO_MASTER_BUSY);
+	ret = qca8k_set_page(priv->bus, page);
 	if (ret)
-		return ret;
+		goto exit;
 
-	val = qca8k_read(priv, QCA8K_MDIO_MASTER_CTRL);
-	if (val < 0)
-		return val;
+	qca8k_mii_write32(priv->bus, 0x10 | r2, r1, val);
+
+	ret = qca8k_mdio_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
+				   QCA8K_MDIO_MASTER_BUSY);
+	if (ret)
+		goto exit;
 
+	val = qca8k_mii_read32(priv->bus, 0x10 | r2, r1);
 	val &= QCA8K_MDIO_MASTER_DATA_MASK;
 
+exit:
+	mutex_unlock(&priv->bus->mdio_lock);
+
+	if (val >= 0)
+		val &= QCA8K_MDIO_MASTER_DATA_MASK;
+
 	/* even if the busy_wait timeouts try to clear the MASTER_EN */
 	qca8k_reg_clear(priv, QCA8K_MDIO_MASTER_CTRL,
 			QCA8K_MDIO_MASTER_EN);
-- 
2.30.2