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xhci: Fix errors in the running total calculations in the TRB math

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Calculations like

	running_total = TRB_MAX_BUFF_SIZE -
		(sg_dma_address(sg) & (TRB_MAX_BUFF_SIZE - 1));
	if (running_total != 0)
		num_trbs++;

are incorrect, because running_total can never be zero, so the if()
expression will never be true. I think the intention was that
running_total be in the range of 0 to TRB_MAX_BUFF_SIZE-1, not 1
to TRB_MAX_BUFF_SIZE. So adding a

	running_total &= TRB_MAX_BUFF_SIZE - 1;

fixes the problem.

This patch should be queued for stable kernels back to 2.6.31.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org
This commit is contained in:
Paul Zimmerman 2011-02-12 14:07:20 -08:00 committed by Sarah Sharp
parent a249018701
commit 5807795bd4
1 changed files with 3 additions and 0 deletions
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3
drivers/usb/host/xhci-ring.c
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@ -2369,6 +2369,7 @@ static unsigned int count_sg_trbs_needed(struct xhci_hcd *xhci, struct urb *urb)
/* Scatter gather list entries may cross 64KB boundaries */
running_total = TRB_MAX_BUFF_SIZE -
(sg_dma_address(sg) & (TRB_MAX_BUFF_SIZE - 1));
running_total &= TRB_MAX_BUFF_SIZE - 1;
if (running_total != 0)
num_trbs++;
@ -2661,6 +2662,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
/* How much data is (potentially) left before the 64KB boundary? */
running_total = TRB_MAX_BUFF_SIZE -
(urb->transfer_dma & (TRB_MAX_BUFF_SIZE - 1));
running_total &= TRB_MAX_BUFF_SIZE - 1;
/* If there's some data on this 64KB chunk, or we have to send a
* zero-length transfer, we need at least one TRB
@ -2884,6 +2886,7 @@ static int count_isoc_trbs_needed(struct xhci_hcd *xhci,
td_len = urb->iso_frame_desc[i].length;
running_total = TRB_MAX_BUFF_SIZE - (addr & (TRB_MAX_BUFF_SIZE - 1));
running_total &= TRB_MAX_BUFF_SIZE - 1;
if (running_total != 0)
num_trbs++;