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

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