Do not rely on any hints from gadget drivers and use DMA mode 1
whenever we expect more data than 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@xxxxxx>
---
drivers/usb/musb/musb_gadget.c | 30 ++++--------------------------
1 files changed, 4 insertions(+), 26 deletions(-)
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index f7194cf..9c94655 100644
--- 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)
len = 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 larger than ep packet_sz
+ * and we have not yet received a short packet
*/
-
- if (request->short_not_ok && len == musb_ep->packet_sz)
+ if ((request->length - request->actual > musb_ep->packet_sz) &&
+ (len >= 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;
--
1.7.4.1
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