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 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..c93fba0a2a7d 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
Hi Pavel,
On Wed, Jul 06, 2022 at 01:50:44PM +0300, Pavel Skripkin 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.
>
> 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 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..c93fba0a2a7d 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);
Can you please indent the arguments to the open bracket?
> }
>
> static void ocelot_fdma_dcb_set_data(struct ocelot_fdma_dcb *dcb,
> --
> 2.35.1
>
Hi Vladimir,
Vladimir Oltean <[email protected]> says:
> Can you please indent the arguments to the open bracket?
>
Sure thing! I've just sent a v4.
Thank you for review
Thanks,
--Pavel Skripkin
On Wed, Jul 06, 2022 at 04:29:45PM +0300, Pavel Skripkin wrote:
> Hi Vladimir,
>
> Vladimir Oltean <[email protected]> says:
> > Can you please indent the arguments to the open bracket?
> >
>
> Sure thing! I've just sent a v4.
>
> Thank you for review
And thank you for the patch!