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

commit 5807795bd4dececdf553719cc02869e633395787 upstream.

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.

[PG: 34 doesn't have count_isoc_trbs_needed() hence this has
only two of the three upstream running_total changes.]

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 8bf55631810176acf34e5e5b1635b238af6381f5..e4afa994257f5008f6117e43c2c44395e177eb89 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1711,6 +1711,7 @@ 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++;
 
@@ -1978,6 +1979,7 @@ 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