[PATCH 4.9 101/240] fotg210-udc: Fix DMA on EP0 for length > max packet size

[Greg Kroah-Hartman]

From: Fabian Vogt <fabian@xxxxxxxxxxxxxx>

[ Upstream commit 755915fc28edfc608fa89a163014acb2f31c1e19 ]

For a 75 Byte request, it would send the first 64 separately, then detect
that the remaining 11 Byte fit into a single DMA, but due to this bug set
the length to the original 75 Bytes. This leads to a DMA failure (which is
ignored...) and the request completes without the remaining bytes having
been sent.

Fixes: b84a8dee23fd ("usb: gadget: add Faraday fotg210_udc driver")
Signed-off-by: Fabian Vogt <fabian@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210324141115.9384-2-fabian@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/usb/gadget/udc/fotg210-udc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/fotg210-udc.c b/drivers/usb/gadget/udc/fotg210-udc.c
index 76e991557116..7831c556a40b 100644
--- a/drivers/usb/gadget/udc/fotg210-udc.c
+++ b/drivers/usb/gadget/udc/fotg210-udc.c
@@ -348,7 +348,7 @@ static void fotg210_start_dma(struct fotg210_ep *ep,
 		if (req->req.length - req->req.actual > ep->ep.maxpacket)
 			length = ep->ep.maxpacket;
 		else
-			length = req->req.length;
+			length = req->req.length - req->req.actual;
 	}
 
 	d = dma_map_single(NULL, buffer, length,
-- 
2.30.2