linux-kernel - [PATCH] imx_udc: don't queue more data when zlp is to be sent

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Date:	Thu, 28 May 2009 13:00:14 +0200
From:	Daniel Glöckner <dg@...ix.com>
To:	Darius Augulis <augulis.darius@...il.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Daniel Glöckner <dg@...ix.com>
Subject: [PATCH] imx_udc: don't queue more data when zlp is to be sent

When a zero-length packet has been requested and another packet is
written into the fifo, the MX1 tends to send the first byte of the
previous packet instead of the first byte of the current packet.
The CRC is adjusted accordingly so that this packet is _not_
discarded by the host.

Waiting for the ZLPS bit to clear avoids these bad packets.

Signed-off-by: Daniel Glöckner <dg@...ix.com>
---
 drivers/usb/gadget/imx_udc.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/gadget/imx_udc.c b/drivers/usb/gadget/imx_udc.c
index ff7658e..642cceb 100644
--- a/drivers/usb/gadget/imx_udc.c
+++ b/drivers/usb/gadget/imx_udc.c
@@ -415,6 +415,13 @@ static int write_packet(struct imx_ep_struct *imx_ep, struct imx_request *req)
 	u8	*buf;
 	int	length, count, temp;
 
+	if (unlikely(__raw_readl(imx_ep->imx_usb->base +
+				 USB_EP_STAT(EP_NO(imx_ep))) & EPSTAT_ZLPS)) {
+		D_TRX(imx_ep->imx_usb->dev, "<%s> zlp still queued in EP %s\n",
+			__func__, imx_ep->ep.name);
+		return -1;
+	}
+
 	buf = req->req.buf + req->req.actual;
 	prefetch(buf);
 
-- 
1.6.1.3

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