usb: musb: use DMA mode 1 whenever possible

Do not rely on any hints from gadget drivers and use DMA mode 1
whenever we expect data of at least the endpoint's packet size and
have not yet received a short packet.

The last packet if short is always transferred using DMA mode 0.

This patch fixes USB throughput issues in mass storage mode for
host to device transfers.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 8d2cce1..5c4392b 100644 (file)
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -707,12 +707,11 @@ static void rxstate(struct musb *musb, struct musb_request *req)
                fifo_count = musb_readw(epio, MUSB_RXCOUNT);
 
                /*
-                * Enable Mode 1 on RX transfers only when short_not_ok flag
-                * is set. Currently short_not_ok flag is set only from
-                * file_storage and f_mass_storage drivers
+                *  use mode 1 only if we expect data of at least ep packet_sz
+                *  and have not yet received a short packet
                 */
-
-               if (request->short_not_ok && fifo_count == musb_ep->packet_sz)
+               if ((request->length - request->actual >= musb_ep->packet_sz) &&
+                       (fifo_count >= musb_ep->packet_sz))
                        use_mode_1 = 1;
                else
                        use_mode_1 = 0;
@@ -727,27 +726,6 @@ static void rxstate(struct musb *musb, struct musb_request *req)
                                c = musb->dma_controller;
                                channel = musb_ep->dma;
 
-       /* We use DMA Req mode 0 in rx_csr, and DMA controller operates in
-        * mode 0 only. So we do not get endpoint interrupts due to DMA
-        * completion. We only get interrupts from DMA controller.
-        *
-        * We could operate in DMA mode 1 if we knew the size of the tranfer
-        * in advance. For mass storage class, request->length = what the host
-        * sends, so that'd work.  But for pretty much everything else,
-        * request->length is routinely more than what the host sends. For
-        * most these gadgets, end of is signified either by a short packet,
-        * or filling the last byte of the buffer.  (Sending extra data in
-        * that last pckate should trigger an overflow fault.)  But in mode 1,
-        * we don't get DMA completion interrupt for short packets.
-        *
-        * Theoretically, we could enable DMAReq irq (MUSB_RXCSR_DMAMODE = 1),
-        * to get endpoint interrupt on every DMA req, but that didn't seem
-        * to work reliably.
-        *
-        * REVISIT an updated g_file_storage can set req->short_not_ok, which
-        * then becomes usable as a runtime "use mode 1" hint...
-        */
-
                                /* Experimental: Mode1 works with mass storage use cases */
                                if (use_mode_1) {
                                        csr |= MUSB_RXCSR_AUTOCLEAR;