diff options
Diffstat (limited to 'drivers/usb/musb/musb_gadget.c')
| -rw-r--r-- | drivers/usb/musb/musb_gadget.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c index d0b87e7b4abf..b6b84dacc791 100644 --- a/drivers/usb/musb/musb_gadget.c +++ b/drivers/usb/musb/musb_gadget.c @@ -707,11 +707,12 @@ static void rxstate(struct musb *musb, struct musb_request *req) fifo_count = musb_readw(epio, MUSB_RXCOUNT); /* - * use mode 1 only if we expect data of at least ep packet_sz - * and have not yet received a short packet + * 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 */ - if ((request->length - request->actual >= musb_ep->packet_sz) && - (fifo_count >= musb_ep->packet_sz)) + + if (request->short_not_ok && fifo_count == musb_ep->packet_sz) use_mode_1 = 1; else use_mode_1 = 0; @@ -727,6 +728,27 @@ 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; |