xhci: Clarify some expressions in the TRB math

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>
Cc: stable@kernel.org

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 2a87231..1071411 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2368,7 +2368,7 @@ 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++;
 
@@ -2399,11 +2399,11 @@ 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,
@@ -2538,8 +2538,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
        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;
@@ -2577,7 +2576,7 @@ 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),
@@ -2621,7 +2620,7 @@ 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 =
@@ -2661,7 +2660,7 @@ 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
@@ -2705,8 +2704,8 @@ 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;
@@ -2884,8 +2883,7 @@ static int count_isoc_trbs_needed(struct xhci_hcd *xhci,
        addr = (u64) (urb->transfer_dma + urb->iso_frame_desc[i].offset);
        td_len = urb->iso_frame_desc[i].length;
 
-       running_total = TRB_MAX_BUFF_SIZE -
-                       (addr & ((1 << TRB_MAX_BUFF_SHIFT) - 1));
+       running_total = TRB_MAX_BUFF_SIZE - (addr & (TRB_MAX_BUFF_SIZE - 1));
        if (running_total != 0)
                num_trbs++;