Re: [PATCH 13/14] drivers: net: dsa: qca8k: protect MASTER busy_wait with mdio mutex

Andrew Lunn
2021-04-23T12:53:21Z

On Fri, Apr 23, 2021 at 03:47:39AM +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 | 59 ++++++++++++++++++++++++++++++++++-------
> 1 file changed, 50 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index 88a0234f1a7b..d2f5e0b1c721 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -609,9 +609,33 @@ 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);

You should really be returning -ETIMEDOUT here on error.

Andrew