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xhci: correct burst count field for isoc transfers on 1.0 xhci hosts

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commit 3213b15138 upstream.

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 5cd43e33b9
"xhci 1.0: Set transfer burst count field."

Suggested-by: ShiChun Ma <masc2008@qq.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mathias Nyman
2014-06-24 17:14:41 +03:00
committed by Greg Kroah-Hartman
parent 58f550fa31
commit 5f84a7feac
1 changed files with 1 additions and 1 deletions
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2
drivers/usb/host/xhci-ring.c
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@@ -3590,7 +3590,7 @@ 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;
}
/*