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Subject[PATCH] [155/275] xhci: Clarify some expressions in the TRB math
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2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Paul Zimmerman <Paul.Zimmerman@synopsys.com>

commit a2490187011cc2263117626615a581927d19f1d3 upstream.

This makes it easier to spot some problems, which will be fixed by the
next patch in the series. Also change dev_dbg to dev_err in
check_trb_math(), so any math errors will be visible even when running
with debug disabled.

Note: This patch changes the expressions containing
"((1 << TRB_MAX_BUFF_SHIFT) - 1)" to use the equivalent
"(TRB_MAX_BUFF_SIZE - 1)". No change in behavior is intended for
those expressions.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
drivers/usb/host/xhci-ring.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

Index: linux-2.6.35.y/drivers/usb/host/xhci-ring.c
===================================================================
--- linux-2.6.35.y.orig/drivers/usb/host/xhci-ring.c 2011-03-29 23:03:01.466262652 -0700
+++ linux-2.6.35.y/drivers/usb/host/xhci-ring.c 2011-03-29 23:54:34.753113182 -0700
@@ -1890,7 +1890,7 @@

/* Scatter gather list entries may cross 64KB boundaries */
running_total = TRB_MAX_BUFF_SIZE -
- (sg_dma_address(sg) & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+ (sg_dma_address(sg) & (TRB_MAX_BUFF_SIZE - 1));
if (running_total != 0)
num_trbs++;

@@ -1920,11 +1920,11 @@
static void check_trb_math(struct urb *urb, int num_trbs, int running_total)
{
if (num_trbs != 0)
- dev_dbg(&urb->dev->dev, "%s - ep %#x - Miscalculated number of "
+ dev_err(&urb->dev->dev, "%s - ep %#x - Miscalculated number of "
"TRBs, %d left\n", __func__,
urb->ep->desc.bEndpointAddress, num_trbs);
if (running_total != urb->transfer_buffer_length)
- dev_dbg(&urb->dev->dev, "%s - ep %#x - Miscalculated tx length, "
+ dev_err(&urb->dev->dev, "%s - ep %#x - Miscalculated tx length, "
"queued %#x (%d), asked for %#x (%d)\n",
__func__,
urb->ep->desc.bEndpointAddress,
@@ -2051,8 +2051,7 @@
sg = urb->sg;
addr = (u64) sg_dma_address(sg);
this_sg_len = sg_dma_len(sg);
- trb_buff_len = TRB_MAX_BUFF_SIZE -
- (addr & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+ trb_buff_len = TRB_MAX_BUFF_SIZE - (addr & (TRB_MAX_BUFF_SIZE - 1));
trb_buff_len = min_t(int, trb_buff_len, this_sg_len);
if (trb_buff_len > urb->transfer_buffer_length)
trb_buff_len = urb->transfer_buffer_length;
@@ -2088,7 +2087,7 @@
(unsigned int) (addr + TRB_MAX_BUFF_SIZE) & ~(TRB_MAX_BUFF_SIZE - 1),
(unsigned int) addr + trb_buff_len);
if (TRB_MAX_BUFF_SIZE -
- (addr & ((1 << TRB_MAX_BUFF_SHIFT) - 1)) < trb_buff_len) {
+ (addr & (TRB_MAX_BUFF_SIZE - 1)) < trb_buff_len) {
xhci_warn(xhci, "WARN: sg dma xfer crosses 64KB boundaries!\n");
xhci_dbg(xhci, "Next boundary at %#x, end dma = %#x\n",
(unsigned int) (addr + TRB_MAX_BUFF_SIZE) & ~(TRB_MAX_BUFF_SIZE - 1),
@@ -2132,7 +2131,7 @@
}

trb_buff_len = TRB_MAX_BUFF_SIZE -
- (addr & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+ (addr & (TRB_MAX_BUFF_SIZE - 1));
trb_buff_len = min_t(int, trb_buff_len, this_sg_len);
if (running_total + trb_buff_len > urb->transfer_buffer_length)
trb_buff_len =
@@ -2171,7 +2170,7 @@
num_trbs = 0;
/* How much data is (potentially) left before the 64KB boundary? */
running_total = TRB_MAX_BUFF_SIZE -
- (urb->transfer_dma & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+ (urb->transfer_dma & (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
@@ -2211,8 +2210,8 @@
/* How much data is in the first TRB? */
addr = (u64) urb->transfer_dma;
trb_buff_len = TRB_MAX_BUFF_SIZE -
- (urb->transfer_dma & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
- if (urb->transfer_buffer_length < trb_buff_len)
+ (urb->transfer_dma & (TRB_MAX_BUFF_SIZE - 1));
+ if (trb_buff_len > urb->transfer_buffer_length)
trb_buff_len = urb->transfer_buffer_length;

first_trb = true;

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