linux-kernel - [PATCH 3.2 48/94] usb: renesas_usbhs: Fix DMAC sequence for receiving zero-length packet

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Date:   Thu, 28 Dec 2017 16:59:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Felipe Balbi" <felipe.balbi@...ux.intel.com>,
        "Kazuya Mizuguchi" <kazuya.mizuguchi.ks@...esas.com>,
        "Yoshihiro Shimoda" <yoshihiro.shimoda.uh@...esas.com>
Subject: [PATCH 3.2 48/94] usb: renesas_usbhs: Fix DMAC sequence for
 receiving zero-length packet

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

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

From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>

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@...esas.com>
[shimoda: revise the commit log]
Fixes: e73a9891b3a1 ("usb: renesas_usbhs: add DMAEngine support")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -817,8 +817,8 @@ static void usbhsf_dma_prepare_tasklet(u
 	dev_dbg(dev, "  %s %d (%d/ %d)\n",
 		fifo->name, usbhs_pipe_number(pipe), pkt->length, pkt->zero);
 
-	usbhsf_dma_start(pipe, fifo);
 	dma_async_issue_pending(chan);
+	usbhsf_dma_start(pipe, fifo);
 
 xfer_work_end:
 	usbhs_unlock(priv, flags);