From 5b1c328619ef9fcc533acf8cd1cf21ab4913b50b Mon Sep 17 00:00:00 2001 From: Furquan Shaikh Date: Sun, 24 Aug 2014 23:07:43 -0700 Subject: [PATCH] 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 Original-Commit-Id: 561bdd746c4d4446ce0a6d21337d354625d85ddc Original-Change-Id: Ic05d47422312a1cddbebe3180f4f159853604440 Original-Signed-off-by: Furquan Shaikh Original-Reviewed-on: https://chromium-review.googlesource.com/213917 Original-Reviewed-by: Aaron Durbin Original-Tested-by: Furquan Shaikh Original-Commit-Queue: Furquan Shaikh Reviewed-on: http://review.coreboot.org/8732 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer --- payloads/libpayload/drivers/usb/ehci.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/payloads/libpayload/drivers/usb/ehci.c b/payloads/libpayload/drivers/usb/ehci.c index b83712c463..7002623e49 100644 --- a/payloads/libpayload/drivers/usb/ehci.c +++ b/payloads/libpayload/drivers/usb/ehci.c @@ -30,6 +30,7 @@ //#define USB_DEBUG #include +#include #include #include "ehci.h" #include "ehci_private.h" @@ -317,6 +318,14 @@ static int wait_for_tds(qtd_t *head) static int ehci_set_async_schedule(ehci_t *ehcic, int enable) { + + /* Memory barrier to ensure that all memory accesses before we set the + * async schedule are complete. It was observed especially in the case of + * arm64, that netboot and usb stuff resulted in lots of errors possibly + * due to CPU reordering. Hence, enforcing strict CPU ordering. + */ + mb(); + /* Set async schedule status. */ if (enable) ehcic->operation->usbcmd |= HC_OP_ASYNC_SCHED_EN;