usb/xhci: Fix timeout logic

This fixes a logic bug in how timeouts are reported back. In the
timeout case, the original code would return -1 instead of 0. All call
sites expect a return value of 0 as the timeout indicator.

Signed-off-by: Caveh Jalali <caveh@chromium.org>
Change-Id: I81a888aa0a1544e55e6a680be8f3b7f6e0d87812
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41854
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/payloads/libpayload/drivers/usb/xhci.c b/payloads/libpayload/drivers/usb/xhci.c
index 07d5b16486..749ff0a066 100644
--- a/payloads/libpayload/drivers/usb/xhci.c
+++ b/payloads/libpayload/drivers/usb/xhci.c
@@ -129,7 +129,12 @@ xhci_switchback_ppt_ports(pcidev_t addr)
 static long
 xhci_handshake(volatile u32 *const reg, u32 mask, u32 wait_for, long timeout_us)
 {
-	while ((*reg & mask) != wait_for && timeout_us--) udelay(1);
+	if (timeout_us <= 0)
+		return 0;
+	while ((*reg & mask) != wait_for && timeout_us != 0) {
+		--timeout_us;
+		udelay(1);
+	}
 	return timeout_us;
 }