[PATCH 3.16 102/204] usb: renesas_usbhs: Fix DMAC sequence for receiving zero-length packet

[Ben Hutchings]

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@xxxxxxxxxxx>

commit 29c7f3e68eec4ae94d85ad7b5dfdafdb8089f513 upstream.

The DREQE bit of the DnFIFOSEL should be set to 1 after the DE bit of
USB-DMAC on R-Car SoCs is set to 1 after the USB-DMAC received a
zero-length packet. Otherwise, a transfer completion interruption
of USB-DMAC doesn't happen. Even if the driver changes the sequence,
normal operations (transmit/receive without zero-length packet) will
not cause any side-effects. So, this patch fixes the sequence anyway.

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@xxxxxxxxxxx>
[shimoda: revise the commit log]
Fixes: e73a9891b3a1 ("usb: renesas_usbhs: add DMAEngine support")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/renesas_usbhs/fifo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/renesas_usbhs/fifo.c
+++ b/drivers/usb/renesas_usbhs/fifo.c
@@ -828,9 +828,9 @@ static void xfer_work(struct work_struct
 	dev_dbg(dev, "  %s %d (%d/ %d)\n",
 		fifo->name, usbhs_pipe_number(pipe), pkt->length, pkt->zero);
 
-	usbhsf_dma_start(pipe, fifo);
 	usbhs_pipe_set_trans_count_if_bulk(pipe, pkt->trans);
 	dma_async_issue_pending(chan);
+	usbhsf_dma_start(pipe, fifo);
 	usbhs_pipe_enable(pipe);
 
 xfer_work_end: