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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>
This commit is contained in:
Roger Quadros 2012-08-07 16:09:56 +03:00 committed by Felipe Balbi
parent 8e8a551654
commit 4f3e8d263d
1 changed files with 4 additions and 26 deletions
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30
drivers/usb/musb/musb_gadget.c
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@ -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;