ice: sleep, don't busy-wait, for ICE_CTL_Q_SQ_CMD_TIMEOUT

The driver polls for ice_sq_done() with a 100 µs period for up to 1 s
and it uses udelay to do that.

Let's use usleep_range instead. We know sleeping is allowed here,
because we're holding a mutex (cq->sq_lock). To preserve the total
max waiting time, measure the timeout in jiffies.

ICE_CTL_Q_SQ_CMD_TIMEOUT is used also in ice_release_res(), but there
the polling period is 1 ms (i.e. 10 times longer). Since the timeout was
expressed in terms of the number of loops, the total timeout in this
function is 10 s. I do not know if this is intentional. This patch keeps
it.

The patch lowers the CPU usage of the ice-gnss-<dev_name> kernel thread
on my system from ~8 % to less than 1 %.

I received a report of high CPU usage with ptp4l where the busy-waiting
in ice_sq_send_cmd dominated the profile. This patch has been tested in
that usecase too and it made a huge improvement there.

Tested-by: Brent Rowsell <browsell@redhat.com>
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

0 files changed, 0 insertions, 0 deletions