commit: 5807795bd4dececdf553719cc02869e633395787
From: Paul Zimmerman <[email protected]>
Date: Sat, 12 Feb 2011 14:07:20 -0800
Subject: [PATCH] xhci: Fix errors in the running total calculations in the TRB
math
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 <[email protected]>
Signed-off-by: Sarah Sharp <[email protected]>
Cc: [email protected]
---
drivers/usb/host/xhci-ring.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 1071411..dbbeec9 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -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++;
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