xhci: Clarify some expressions in the TRB math

commit a2490187 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>

drivers/usb/host/xhci-ring.c

@@ -1490,7 +1490,7 @@ 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) & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+			(sg_dma_address(sg) & (TRB_MAX_BUFF_SIZE - 1));
 		if (running_total != 0)
 			num_trbs++;
 
@@ -1520,11 +1520,11 @@ static unsigned int count_sg_trbs_needed(struct xhci_hcd *xhci, struct urb *urb)
 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,
@@ -1631,8 +1631,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	sg = urb->sg->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;
@@ -1667,7 +1666,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 				(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),
@@ -1705,7 +1704,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		}
 
 		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 =
@@ -1740,7 +1739,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	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
@@ -1779,8 +1778,8 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	/* 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;