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    Subject[PATCH 5.18 068/231] net: ocelot: fix wrong time_after usage
    Date
    From: Pavel Skripkin <paskripkin@gmail.com>

    [ Upstream commit f46fd3d7c3bd5d7bd5bb664135cf32ca9e97190b ]

    Accidentally noticed, that this driver is the only user of
    while (time_after(jiffies...)).

    It looks like typo, because likely this while loop will finish after 1st
    iteration, because time_after() returns true when 1st argument _is after_
    2nd one.

    There is one possible problem with this poll loop: the scheduler could put
    the thread to sleep, and it does not get woken up for
    OCELOT_FDMA_CH_SAFE_TIMEOUT_US. During that time, the hardware has done
    its thing, but you exit the while loop and return -ETIMEDOUT.

    Fix it by using sane poll API that avoids all problems described above

    Fixes: 753a026cfec1 ("net: ocelot: add FDMA support")
    Suggested-by: Andrew Lunn <andrew@lunn.ch>
    Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
    Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
    Link: https://lore.kernel.org/r/20220706132845.27968-1-paskripkin@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/ethernet/mscc/ocelot_fdma.c | 17 ++++++++---------
    1 file changed, 8 insertions(+), 9 deletions(-)

    diff --git a/drivers/net/ethernet/mscc/ocelot_fdma.c b/drivers/net/ethernet/mscc/ocelot_fdma.c
    index dffa597bffe6..6a8f84f325a3 100644
    --- a/drivers/net/ethernet/mscc/ocelot_fdma.c
    +++ b/drivers/net/ethernet/mscc/ocelot_fdma.c
    @@ -94,19 +94,18 @@ static void ocelot_fdma_activate_chan(struct ocelot *ocelot, dma_addr_t dma,
    ocelot_fdma_writel(ocelot, MSCC_FDMA_CH_ACTIVATE, BIT(chan));
    }

    +static u32 ocelot_fdma_read_ch_safe(struct ocelot *ocelot)
    +{
    + return ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE);
    +}
    +
    static int ocelot_fdma_wait_chan_safe(struct ocelot *ocelot, int chan)
    {
    - unsigned long timeout;
    u32 safe;

    - timeout = jiffies + usecs_to_jiffies(OCELOT_FDMA_CH_SAFE_TIMEOUT_US);
    - do {
    - safe = ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE);
    - if (safe & BIT(chan))
    - return 0;
    - } while (time_after(jiffies, timeout));
    -
    - return -ETIMEDOUT;
    + return readx_poll_timeout_atomic(ocelot_fdma_read_ch_safe, ocelot, safe,
    + safe & BIT(chan), 0,
    + OCELOT_FDMA_CH_SAFE_TIMEOUT_US);
    }

    static void ocelot_fdma_dcb_set_data(struct ocelot_fdma_dcb *dcb,
    --
    2.35.1


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