Messages in this thread Patch in this message | | | From | Mathias Nyman <> | Subject | [PATCH 2/5] xhci: correct burst count field for isoc transfers on 1.0 xhci hosts | Date | Tue, 24 Jun 2014 17:14:41 +0300 |
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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@vger.kernel.org # 3.0 Suggested-by: ShiChun Ma <masc2008@qq.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> --- 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
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