[PATCH] usb: cdns3: cdns3-gadget: Fix cdns3_ep_config() by setting ep.maxpacket

[Siddharth Vadapalli]

The function cdns3_ep_config() calculates the maximum packet size based
on the Endpoint Type and the Gadget Speed and stores it in the variable
"max_packet_size". This value is then programmed in the USB Controller
for the corresponding Endpoint. This may result in a mismatch between
the maximum packet size programmed in the USB controller and the maximum
packet size seen by the UDC Core via "maxpacket" member of "struct usb_ep".
Additionally, since TD_SIZE as well as TOTAL_TDL are calculated in
cdns3_ep_run_transfer() on the basis of the maximum packet size stored in
the "maxpacket" member of "struct usb_ep", it may lead to incorrect values
of TD_SIZE and TOTAL_TDL when compared with what the USB controller
actually expects (max_packet_size). This also applies to the calculation of
TDL in cdns3_ep_run_stream_transfer().

Fix this.

Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
---

Hello,

This patch is based on commit
1d227fcc7222 Merge tag 'net-6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
of Mainline Linux.

Regards,
Siddharth.

 drivers/usb/cdns3/cdns3-gadget.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index fd1beb10bba7..e89bd248e81d 100644
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -2145,6 +2145,16 @@ int cdns3_ep_config(struct cdns3_endpoint *priv_ep, bool enable)
 		return -EINVAL;
 	}
 
+	/*
+	 * The Endpoint is configured to handle a maximum packet size of
+	 * max_packet_size. Hence, set priv_ep->endpoint.maxpacket to
+	 * max_packet_size. This is necessary to ensure that TD_SIZE and
+	 * TOTAL_TDL are calculated correctly in cdns3_ep_run_transfer(),
+	 * and also to ensure that TDL is calculated correctly in
+	 * cdns3_ep_run_stream_transfer().
+	 */
+	priv_ep->endpoint.maxpacket = max_packet_size;
+
 	if (max_packet_size == 1024)
 		priv_ep->trb_burst_size = 128;
 	else if (max_packet_size >= 512)
-- 
2.40.1