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,