Enable Mode1 for RX transfers.
This should give a boost of about 30% with g_file_storage.
Add a module param to enable this mode - by default, we keep
the old way (Mode0) so as not to break anything.
To enable this, `echo 1 > /sys/module/musb_hdrc/parameters/dma_mode1_rx`.
To change back, echo 0 to the same node.
NYET-Signed-off-by: Anand Gadiyar <gadiyar@xxxxxx>
NYET-Signed-off-by: Maulik Mankad <x0082077@xxxxxx>
CC: Cliff Cai <cliffcai.sh@xxxxxxxxx>
---
drivers/usb/musb/musb_gadget.c | 67 +++++++++++++++++++++++++++++------------
1 file changed, 48 insertions(+), 19 deletions(-)
Index: kernel-omap3-dev/drivers/usb/musb/musb_gadget.c
===================================================================
--- kernel-omap3-dev.orig/drivers/usb/musb/musb_gadget.c
+++ kernel-omap3-dev/drivers/usb/musb/musb_gadget.c
@@ -561,6 +561,19 @@ void musb_g_tx(struct musb *musb, u8 epn
#endif
/*
+ * Enable DMA Mode 1 for RX transfers. This works reliably only
+ * with g_file_storage at the moment. Enabling this feature will
+ * result in a performance gain of about 30% for at least
+ * g_file_storage use cases.
+ * Making it a module parameter for overriding the short_not_ok check.
+ * so that this can be tested with g_zero, etc.
+ */
+static int musb_use_dma_mode1_rx;
+module_param_named(dma_mode1_rx, musb_use_dma_mode1_rx, bool,
+ S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(dma_mode1_rx, "Enable Mode 1 for RX transfers. Default = n");
+
+/*
* Context: controller locked, IRQs blocked, endpoint selected
*/
static void rxstate(struct musb *musb, struct musb_request *req)
@@ -572,6 +585,7 @@ static void rxstate(struct musb *musb, s
unsigned fifo_count = 0;
u16 len = musb_ep->packet_sz;
u16 csr = musb_readw(epio, MUSB_RXCSR);
+ int use_mode_1 = 0;
/* We shouldn't get here while DMA is active, but we do... */
if (dma_channel_status(musb_ep->dma) == MUSB_DMA_STATUS_BUSY) {
@@ -614,6 +628,20 @@ static void rxstate(struct musb *musb, s
if (csr & MUSB_RXCSR_RXPKTRDY) {
len = musb_readw(epio, MUSB_RXCOUNT);
+
+ /*
+ * Alternatively, we can check request->short_not_ok,
+ * which is true only for g_file_storage. This way
+ * we use mode1 for the only gadget where it works
+ * reliably, and all others use mode0
+ *
+ * This module param way is only for testing.
+ */
+ if (musb_use_dma_mode1_rx && len == musb_ep->packet_sz)
+ use_mode_1 = 1;
+ else
+ use_mode_1 = 0;
+
if (request->actual < request->length) {
#ifdef CONFIG_USB_INVENTRA_DMA
if (is_dma_capable() && musb_ep->dma) {
@@ -645,28 +673,29 @@ static void rxstate(struct musb *musb, s
* then becomes usable as a runtime "use mode 1" hint...
*/
- csr |= MUSB_RXCSR_DMAENAB;
-#ifdef USE_MODE1
- csr |= MUSB_RXCSR_AUTOCLEAR;
- /* csr |= MUSB_RXCSR_DMAMODE; */
-
- /* this special sequence (enabling and then
- * disabling MUSB_RXCSR_DMAMODE) is required
- * to get DMAReq to activate
- */
- musb_writew(epio, MUSB_RXCSR,
- csr | MUSB_RXCSR_DMAMODE);
-#endif
- musb_writew(epio, MUSB_RXCSR, csr);
+ /*
+ * Experimental: Mode1 works with g_file_storage use cases
+ * For other drivers, it appears that sometimes an end-point
+ * interrupt is received before the DMA completion interrupt
+ *
+ */
+ if (use_mode_1) {
+ csr |= MUSB_RXCSR_AUTOCLEAR;
+ csr |= MUSB_RXCSR_DMAENAB;
+ musb_writew(epio, MUSB_RXCSR, csr);
+ csr |= MUSB_RXCSR_DMAMODE;
+ musb_writew(epio, MUSB_RXCSR, csr);
+ } else {
+ csr |= MUSB_RXCSR_DMAENAB;
+ musb_writew(epio, MUSB_RXCSR, csr);
+ }
if (request->actual < request->length) {
int transfer_size = 0;
-#ifdef USE_MODE1
- transfer_size = min(request->length,
- channel->max_len);
-#else
- transfer_size = len;
-#endif
+ transfer_size = use_mode_1 ?
+ min(request->length,
+ channel->max_len) : len;
+
if (transfer_size <= musb_ep->packet_sz)
musb_ep->dma->desired_mode = 0;
else
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
