net: ocelot: fix wrong time_after usage

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: 63f3021bd722 ("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>

diff --git a/drivers/net/ethernet/mscc/ocelot_fdma.c b/drivers/net/ethernet/mscc/ocelot_fdma.c
index 083fddd263ec620207d852f9acc05b9a0c71f899..8e3894cf5f7cd3ee469f26bb305c9f0a72962c55 100644 (file)
--- 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,