From: Michael Hennerich <michael.hennerich@xxxxxxxxxx> The ISP1760 has some timing requirements where it has to delay a short period after a write to a register has started. However, this delay is from the time the write hits the USB chip (the ISP1760), not from the time where the processor started processing the write. So on a quick enough processor, it is sometimes possible for the write to not hit the device before we start delaying, and we then violate the part's timing requirements, so things stop working. To avoid all this, insert a write barrier after the register write and before the timing delay/register read so we can guarantee we only start counting time after the write has hit the device. Signed-off-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx> Signed-off-by: Mike Frysinger <vapier@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx> --- drivers/usb/host/isp1760-hcd.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c index d1a3dfc..bdba8c5 100644 --- a/drivers/usb/host/isp1760-hcd.c +++ b/drivers/usb/host/isp1760-hcd.c @@ -829,6 +829,7 @@ static void enqueue_an_ATL_packet(struct usb_hcd *hcd, struct isp1760_qh *qh, * almost immediately. With ISP1761, this register requires a delay of * 195ns between a write and subsequent read (see section 15.1.1.3). */ + mmiowb(); ndelay(195); skip_map = isp1760_readl(hcd->regs + HC_ATL_PTD_SKIPMAP_REG); @@ -870,6 +871,7 @@ static void enqueue_an_INT_packet(struct usb_hcd *hcd, struct isp1760_qh *qh, * almost immediately. With ISP1761, this register requires a delay of * 195ns between a write and subsequent read (see section 15.1.1.3). */ + mmiowb(); ndelay(195); skip_map = isp1760_readl(hcd->regs + HC_INT_PTD_SKIPMAP_REG); -- 1.7.2 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
