[PATCH] USB: UHCI: Do short packet detection correctly

This patch makes some simple changes to the way the UHCI driver does short
packet detection.  The current implementation is incorrect in several
ways:

	The Short-Packet-Detect flag is set for OUT transfers, which
	yields undefined behavior according to the UHCI spec.

	It's not set for URBs with URB_SHORT_NOT_OK, which is just the
	opposite of what we want!  Those are the ones where short packets
	do matter.

	It is set for the last packet in a transfer, which causes an
	unnecessary pause in the data flow (except of course that the
	pause _is_ necessary when URB_SHORT_NOT_OK is set).

The patch also implements the URB_NO_INTERRUPT flag for bulk transfers,
which can help improve system performance by reducing interrupt overhead.

diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
index a8182d88e7b2bbcec07262cac2ccad0ba96fdabf..2c4de26d8a2648b8331f6e898312153e8b5928a4 100644 (file)
--- a/drivers/usb/host/uhci-hcd.c
+++ b/drivers/usb/host/uhci-hcd.c
@@ -840,13 +840,16 @@ static int uhci_submit_control(struct uhci_hcd *uhci, struct urb *urb, struct ur
                urb->setup_dma);
 
        /*
-        * If direction is "send", change the frame from SETUP (0x2D)
-        * to OUT (0xE1). Else change it from SETUP to IN (0x69).
+        * If direction is "send", change the packet ID from SETUP (0x2D)
+        * to OUT (0xE1).  Else change it from SETUP to IN (0x69) and
+        * set Short Packet Detect (SPD) for all data packets.
         */
-       destination ^= (USB_PID_SETUP ^ usb_packetid(urb->pipe));
-
-       if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
+       if (usb_pipeout(urb->pipe))
+               destination ^= (USB_PID_SETUP ^ USB_PID_OUT);
+       else {
+               destination ^= (USB_PID_SETUP ^ USB_PID_IN);
                status |= TD_CTRL_SPD;
+       }
 
        /*
         * Build the DATA TD's
@@ -1101,17 +1104,20 @@ static int uhci_submit_common(struct uhci_hcd *uhci, struct urb *urb, struct urb
        status = uhci_maxerr(3) | TD_CTRL_ACTIVE;
        if (urb->dev->speed == USB_SPEED_LOW)
                status |= TD_CTRL_LS;
-       if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
+       if (usb_pipein(urb->pipe))
                status |= TD_CTRL_SPD;
 
        /*
         * Build the DATA TD's
         */
        do {    /* Allow zero length packets */
-               int pktsze = len;
+               int pktsze = maxsze;
 
-               if (pktsze > maxsze)
-                       pktsze = maxsze;
+               if (pktsze >= len) {
+                       pktsze = len;
+                       if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
+                               status &= ~TD_CTRL_SPD;
+               }
 
                td = uhci_alloc_td(uhci, urb->dev);
                if (!td)
@@ -1154,7 +1160,8 @@ static int uhci_submit_common(struct uhci_hcd *uhci, struct urb *urb, struct urb
        }
 
        /* Set the flag on the last packet */
-       td->status |= cpu_to_le32(TD_CTRL_IOC);
+       if (!(urb->transfer_flags & URB_NO_INTERRUPT))
+               td->status |= cpu_to_le32(TD_CTRL_IOC);
 
        qh = uhci_alloc_qh(uhci, urb->dev);
        if (!qh)