[PATCH v2 2/3] usb: chipidea: udc: limit usb request length to max 16KB

[Xu Yang <xu.yang_2@nxp.com>]

To let the device controller work properly on short packet limitations,
one usb request should only correspond to one dTD. Then every dTD will
set IOC. In theory, each dTD support up to 20KB data transfer if the
offset is 0. Due to we cannot predetermine the offset, this will limit
the usb request length to max 16KB. This should be fine since most of
the user transfer data based on this size policy.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v2:
 - limit request length only when ci->has_short_pkt_limit set
 - modify commit message
---
 drivers/usb/chipidea/ci.h  | 1 +
 drivers/usb/chipidea/udc.c | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/drivers/usb/chipidea/ci.h b/drivers/usb/chipidea/ci.h
index e4b003d060c2..97437de52ef6 100644
--- a/drivers/usb/chipidea/ci.h
+++ b/drivers/usb/chipidea/ci.h
@@ -25,6 +25,7 @@
 #define TD_PAGE_COUNT      5
 #define CI_HDRC_PAGE_SIZE  4096ul /* page size for TD's */
 #define ENDPT_MAX          32
+#define CI_MAX_REQ_SIZE	(4 * CI_HDRC_PAGE_SIZE)
 #define CI_MAX_BUF_SIZE	(TD_PAGE_COUNT * CI_HDRC_PAGE_SIZE)
 
 /******************************************************************************
diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index 18c1882cf088..5badb39cb2bf 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -972,6 +972,12 @@ static int _ep_queue(struct usb_ep *ep, struct usb_request *req,
 		return -EMSGSIZE;
 	}
 
+	if (ci->has_short_pkt_limit &&
+		hwreq->req.length > CI_MAX_REQ_SIZE) {
+		dev_err(hwep->ci->dev, "request length too big (max 16KB)\n");
+		return -EMSGSIZE;
+	}
+
 	/* first nuke then test link, e.g. previous status has not sent */
 	if (!list_empty(&hwreq->queue)) {
 		dev_err(hwep->ci->dev, "request already in queue\n");
-- 
2.34.1