usb: musb: cppi41: don't check early-TX-interrupt for Isoch transfer

commit 0090114d336a9604aa2d90bc83f20f7cd121b76c upstream.

The CPPI 4.1 driver polls register to workaround the premature TX
interrupt issue, but it causes audio playback underrun when triggered in
Isoch transfers.

Isoch doesn't do back-to-back transfers, the TX should be done by the
time the next transfer is scheduled. So skip this polling workaround for
Isoch transfer.

Fixes: a655f481d83d6 ("usb: musb: musb_cppi41: handle pre-mature TX complete interrupt")
Reported-by: Alexandre Bailon <abailon@baylibre.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Alexandre Bailon <abailon@baylibre.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 16363852c0346b28b6452e04eddedfc630635428..cac3b21a720b7f5d27ca6c221d9341dbb60893c3 100644 (file)
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -231,8 +231,27 @@ static void cppi41_dma_callback(void *private_data)
                        transferred < cppi41_channel->packet_sz)
                cppi41_channel->prog_len = 0;
 
-       if (cppi41_channel->is_tx)
-               empty = musb_is_tx_fifo_empty(hw_ep);
+       if (cppi41_channel->is_tx) {
+               u8 type;
+
+               if (is_host_active(musb))
+                       type = hw_ep->out_qh->type;
+               else
+                       type = hw_ep->ep_in.type;
+
+               if (type == USB_ENDPOINT_XFER_ISOC)
+                       /*
+                        * Don't use the early-TX-interrupt workaround below
+                        * for Isoch transfter. Since Isoch are periodic
+                        * transfer, by the time the next transfer is
+                        * scheduled, the current one should be done already.
+                        *
+                        * This avoids audio playback underrun issue.
+                        */
+                       empty = true;
+               else
+                       empty = musb_is_tx_fifo_empty(hw_ep);
+       }
 
        if (!cppi41_channel->is_tx || empty) {
                cppi41_trans_done(cppi41_channel);