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 <[email protected]>
Signed-off-by: Pavel Skripkin <[email protected]>
---
Changes since v3:
- Aligned the arguments to the open bracket
Changes since v2:
- Use _atomic variant of readx_poll_timeout
Changes since v1:
- Fixed typos in title and commit message
- Remove while loop and use readx_poll_timeout as suggested by
Andrew
---
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 083fddd263ec..8e3894cf5f7c 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,
--
2.36.1
Hello:
This patch was applied to netdev/net.git (master)
by Jakub Kicinski <[email protected]>:
On Wed, 6 Jul 2022 16:28:45 +0300 you wrote:
> 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.
>
> [...]
Here is the summary with links:
- [v4] net: ocelot: fix wrong time_after usage
https://git.kernel.org/netdev/net/c/f46fd3d7c3bd
You are awesome, thank you!
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