xhci: dbc: Avoid event polling busyloop if pending rx transfers are inactive.

[ Upstream commit cab63934 ]

Event polling delay is set to 0 if there are any pending requests in
either rx or tx requests lists. Checking for pending requests does
not work well for "IN" transfers as the tty driver always queues
requests to the list and TRBs to the ring, preparing to receive data
from the host.

This causes unnecessary busylooping and cpu hogging.

Only set the event polling delay to 0 if there are pending tx "write"
transfers, or if it was less than 10ms since last active data transfer
in any direction.

Cc: Łukasz Bartosik <ukaszb@chromium.org>
Fixes: fb18e5bb ("xhci: dbc: poll at different rate depending on data transfer activity")
Cc: stable@vger.kernel.org
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250505125630.561699-3-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: f3d12ec8 ("xhci: dbc: fix bogus 1024 byte prefix if ttyDBC read races with stall event")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>