This is to reduce the overhead of dma programming for zero byte
transmit as same can be done using pio mode.
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@xxxxxx>
---
drivers/usb/musb/musb_host.c | 12 +++++++++++-
1 files changed, 11 insertions(+), 1 deletions(-)
diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 338947c..351f72a 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -693,6 +693,8 @@ static void musb_ep_program(struct musb *musb, u8 epnum,
void __iomem *epio = hw_ep->regs;
struct musb_qh *qh = musb_ep_get_qh(hw_ep, !is_out);
u16 packet_sz = qh->maxpacket;
+ u8 use_dma = 1;
+ u16 csr;
dev_dbg(musb->controller, "%s hw%d urb %p spd%d dev%d ep%d%s "
"h_addr%02x h_port%02x bytes %d\n",
@@ -704,9 +706,17 @@ static void musb_ep_program(struct musb *musb, u8 epnum,
musb_ep_select(mbase, epnum);
+ if (is_out && !len) {
+ use_dma = 0;
+ csr = musb_readw(epio, MUSB_TXCSR);
+ csr &= ~MUSB_TXCSR_DMAENAB;
+ musb_writew(epio, MUSB_TXCSR, csr);
+ hw_ep->tx_channel = NULL;
+ }
+
/* candidate for DMA? */
dma_controller = musb->dma_controller;
- if (is_dma_capable() && epnum && dma_controller) {
+ if (use_dma && is_dma_capable() && epnum && dma_controller) {
dma_channel = is_out ? hw_ep->tx_channel : hw_ep->rx_channel;
if (!dma_channel) {
dma_channel = dma_controller->channel_alloc(
--
1.7.0.4
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