libpayload EHCI: Add memory barrier to EHCI driver

EHCI driver accesses mmio space using regular struct pointers. In order to avoid
any CPU re-ordering, memory barrier is required in async_set_schedule,
especially for arm64. Without the memory barrier, there seems to be re-ordering
taking place which leads to USB errors with some flash drives as well as
transfer errors in netboot.

BUG=chrome-os-partner:31533
BRANCH=None
TEST=With the memory barrier introduced, netboot for ryu completes transfer
without any error and finishes within 6-7 seconds.

Change-Id: Ib6d29dc79fd5722c27284478e8da316929e86bff
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 561bdd746c4d4446ce0a6d21337d354625d85ddc
Original-Change-Id: Ic05d47422312a1cddbebe3180f4f159853604440
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/213917
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/8732
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions