The transfer burst count (TBC) field in xhci 1.0 hosts should be set to the number of bursts needed to transfer all packets in a isoc TD. Supported values are 0-2 (1 to 3 bursts per service interval). Formula for TBC calculation is given in xhci spec section 4.11.2.3: TBC = roundup( Transfer Descriptor Packet Count / Max Burst Size +1 ) - 1 This patch should be applied to stable kernels since 3.0 that contain the commit 5cd43e33b9519143f06f507dd7cbee6b7a621885 "xhci 1.0: Set transfer burst count field." Cc: stable@xxxxxxxxxxxxxxx # 3.0 Suggested-by: ShiChun Ma <masc2008@xxxxxx> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> --- drivers/usb/host/xhci-ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 71657d3..749fc68 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -3537,7 +3537,7 @@ static unsigned int xhci_get_burst_count(struct xhci_hcd *xhci, return 0; max_burst = urb->ep->ss_ep_comp.bMaxBurst; - return roundup(total_packet_count, max_burst + 1) - 1; + return DIV_ROUND_UP(total_packet_count, max_burst + 1) - 1; } /* -- 1.8.3.2 -- 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
