USB: EHCI: don't send Clear-TT-Buffer following a STALL

commit c2f6595fbdb408d3d6850cfae590c8fa93e27399 upstream.

This patch (as1304) fixes a regression in ehci-hcd.  Evidently some
hubs don't handle Clear-TT-Buffer requests correctly, so we should
avoid sending them when they don't appear to be absolutely necessary.
The reported symptom is that output on a downstream audio device cuts
out because the hub stops relaying isochronous packets.

The patch prevents Clear-TT-Buffer requests from being sent following
a STALL handshake.  In theory a STALL indicates either that the
downstream device sent a STALL or that no matching TT buffer could be
found.  In either case, the transfer is completed and the TT buffer
does not remain busy, so it doesn't need to be cleared.

Also, the patch fixes a minor flaw in the code that actually sends the
Clear-TT-Buffer requests.  Although the pipe direction isn't really
used for control transfers, it should be a Send rather than a Receive.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Javier Kohen <jkohen@users.sourceforge.net>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 71f86c60d83c3962cf8b7eabe1d709d2d87b7a76..b41989e0c6c13039b266f88aae6842798f12c4c5 100644 (file)
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -439,7 +439,7 @@ resubmit:
 static inline int
 hub_clear_tt_buffer (struct usb_device *hdev, u16 devinfo, u16 tt)
 {
-       return usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
+       return usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
                               HUB_CLEAR_TT_BUFFER, USB_RT_PORT, devinfo,
                               tt, NULL, 0, 1000);
 }

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 7673554fa64df28317e4edb9e97eecedd3272fc8..6b6c240cbe7289ae23df2e188702166deae2185d 100644 (file)
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -475,8 +475,20 @@ halt:
                         * we must clear the TT buffer (11.17.5).
                         */
                        if (unlikely(last_status != -EINPROGRESS &&
-                                       last_status != -EREMOTEIO))
-                               ehci_clear_tt_buffer(ehci, qh, urb, token);
+                                       last_status != -EREMOTEIO)) {
+                               /* The TT's in some hubs malfunction when they
+                                * receive this request following a STALL (they
+                                * stop sending isochronous packets).  Since a
+                                * STALL can't leave the TT buffer in a busy
+                                * state (if you believe Figures 11-48 - 11-51
+                                * in the USB 2.0 spec), we won't clear the TT
+                                * buffer in this case.  Strictly speaking this
+                                * is a violation of the spec.
+                                */
+                               if (last_status != -EPIPE)
+                                       ehci_clear_tt_buffer(ehci, qh, urb,
+                                                       token);
+                       }
                }
 
                /* if we're removing something not at the queue head,