[RFC PATCH net-next v3 15/20] net: dsa: qca8k: dsa: qca8k: protect MASTER busy_wait with mdio mutex

From: Ansuel Smith
Date: Tue May 04 2021 - 18:30:56 EST


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 | 69 ++++++++++++++++++++++++++++++++++-------
1 file changed, 57 insertions(+), 12 deletions(-)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index b21835d719b5..27234dd4c74a 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -633,9 +633,33 @@ qca8k_port_to_phy(int port)
return port - 1;
}

+static int
+qca8k_mdio_busy_wait(struct qca8k_priv *priv, u32 reg, u32 mask)
+{
+ unsigned long timeout;
+ u16 r1, r2, page;
+
+ qca8k_split_addr(reg, &r1, &r2, &page);
+
+ timeout = jiffies + msecs_to_jiffies(20);
+
+ /* loop until the busy flag has cleared */
+ do {
+ u32 val = qca8k_mii_read32(priv->bus, 0x10 | r2, r1);
+ int busy = val & mask;
+
+ if (!busy)
+ break;
+ cond_resched();
+ } while (!time_after_eq(jiffies, timeout));
+
+ return time_after_eq(jiffies, timeout);
+}
+
static int
qca8k_mdio_write(struct qca8k_priv *priv, int port, u32 regnum, u16 data)
{
+ u16 r1, r2, page;
u32 phy, val;
int ret;

@@ -651,12 +675,22 @@ 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;

- ret = qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
- QCA8K_MDIO_MASTER_BUSY);
+ qca8k_mii_write32(priv->bus, 0x10 | r2, r1, val);
+
+ if (qca8k_mdio_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
+ QCA8K_MDIO_MASTER_BUSY))
+ ret = -ETIMEDOUT;
+
+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,
@@ -668,6 +702,7 @@ 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;

@@ -682,20 +717,30 @@ 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);
+ 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;

- if (qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
- QCA8K_MDIO_MASTER_BUSY))
- return -ETIMEDOUT;
+ qca8k_mii_write32(priv->bus, 0x10 | r2, r1, val);

- val = qca8k_read(priv, QCA8K_MDIO_MASTER_CTRL);
- if (val < 0)
- return val;
+ if (qca8k_mdio_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
+ QCA8K_MDIO_MASTER_BUSY))
+ val = -ETIMEDOUT;
+ else
+ 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