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

Andrew Lunn
2021-05-05T01:04:53Z

On Wed, May 05, 2021 at 12:29:09AM +0200, Ansuel Smith wrote:
> 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@gmail.com>
> ---
> 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));

include/linux/iopoll.h

> +
> + 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;

qca8k_mdio_busy_wait() should be returning -EIMEDOUT.

Andrew