usb: musb: workaround toggle bug when doing bulk transfer after isoc

This patch implements the work around for a Mentor controller related
bug where it's observed a BULK Tx toggle error on the bus when a
BULK IO gets scheduled on an endpoint that was earlier used for
handling ISOC transaction and needed to start on 1 toggle.  When such
a situation arises even if the TXCSR toggle bits are programmed
correctly by the musb driver the data gets transmitted with 0 toggle
which leads to toggle error on the bus and the BULK transaction fails.
In case of MSC write, the device gets reset by the Host.

This Mentor bug is observed on almost all Mentor versions (1.3, 1.5,
1.8).  Confirmed on DM644x, DM355, DM365, OMAPL13x platforms.

Signed-off-by: Swaminathan S <swami.iyer@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 74c4c3698f1e..c3fdd6d69f5e 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1771,6 +1771,9 @@ static int musb_schedule(
         int                     best_end, epnum;
         struct musb_hw_ep       *hw_ep = NULL;
         struct list_head        *head = NULL;
+        u8                      toggle;
+        u8                      txtype;
+        struct urb              *urb = next_urb(qh);
 
         /* use fixed hardware for control and bulk */
         if (qh->type == USB_ENDPOINT_XFER_CONTROL) {
@@ -1809,6 +1812,27 @@ static int musb_schedule(
                 diff -= (qh->maxpacket * qh->hb_mult);
 
                 if (diff >= 0 && best_diff > diff) {
+
+                        /*
+                         * Mentor controller has a bug in that if we schedule
+                         * a BULK Tx transfer on an endpoint that had earlier
+                         * handled ISOC then the BULK transfer has to start on
+                         * a zero toggle.  If the BULK transfer starts on a 1
+                         * toggle then this transfer will fail as the mentor
+                         * controller starts the Bulk transfer on a 0 toggle
+                         * irrespective of the programming of the toggle bits
+                         * in the TXCSR register.  Check for this condition
+                         * while allocating the EP for a Tx Bulk transfer.  If
+                         * so skip this EP.
+                         */
+                        hw_ep = musb->endpoints + epnum;
+                        toggle = usb_gettoggle(urb->dev, qh->epnum, !is_in);
+                        txtype = (musb_readb(hw_ep->regs, MUSB_TXTYPE)
+                                        >> 4) & 0x3;
+                        if (!is_in && (qh->type == USB_ENDPOINT_XFER_BULK) &&
+                                toggle && (txtype == USB_ENDPOINT_XFER_ISOC))
+                                continue;
+
                         best_diff = diff;
                         best_end = epnum;
                 }