[PATCH 1/2] usb: chipidea: udc: limit usb request length to max 16KB

Xu Yang
2024-09-12T04:50:59Z

Currently, the deivice controller has below limitations:
1. can't generate short packet interrupt if IOC not set in dTD. So if one
request span more than one dTDs and only the last dTD set IOC, the usb
request will pending there if no more data comes.
2. the controller can't accurately deliver data to differtent usb requests
in some cases due to short packet. For example: one usb request span 3
dTDs, then if the controller received a short packet the next packet
will go to 2nd dTD of current request rather than the first dTD of next
request.

To let the device controller work properly, 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.

Although these limitations found on OUT eps, we can put the request to IN
eps too, this will benefit the following patches.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
---
drivers/usb/chipidea/ci.h | 1 +
drivers/usb/chipidea/udc.c | 5 +++++
2 files changed, 6 insertions(+)

diff --git a/drivers/usb/chipidea/ci.h b/drivers/usb/chipidea/ci.h
index 2a38e1eb6546..f8deccfc8713 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 b1a1be6439b6..5d9369d01065 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -969,6 +969,11 @@ static int _ep_queue(struct usb_ep *ep, struct usb_request *req,
return -EMSGSIZE;
}

+ if (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