[PATCH v2] usb: gadget: cdns3: 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 is 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 an incorrect value of TD_SIZE when compared
with what the USB controller actually expects (max_packet_size).

Fix this.

Fixes: 7e91f6ccdc84 ("usb: Add Cadence USB3 host and gadget driver")
Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
---

Hello,

This patch is based on commit
dd4d130c8e clk: renesas: rcar-gen3: Fix SSCG caching replacement with MDSEL/PE caching
of the master branch of U-Boot.

v1:
https://patchwork.ozlabs.org/project/uboot/patch/20241007104239.1624430-1-s-vadapalli@ti.com/
Changes since v1:
- Based on Roger's feedback at:
  https://patchwork.ozlabs.org/project/uboot/patch/20241007104239.1624430-1-s-vadapalli@ti.com/#3389960
  rather than using usb_ep_set_maxpacket_limit() which changes
  "maxpacket_limit" in addition to "maxpacket", only update the "maxpacket"
  member of usb_ep.

Regards,
Siddharth.

 drivers/usb/cdns3/gadget.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
index ac7e469469..a30c40ef80 100644
--- a/drivers/usb/cdns3/gadget.c
+++ b/drivers/usb/cdns3/gadget.c
@@ -1637,6 +1637,14 @@ void cdns3_ep_config(struct cdns3_endpoint *priv_ep)
 	else
 		priv_ep->trb_burst_size = 16;
 
+	/*
+	 * 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 the TD_SIZE
+	 * is calculated correctly in cdns3_ep_run_transfer().
+	 */
+	priv_ep->endpoint.maxpacket = max_packet_size;
+
 	ret = cdns3_ep_onchip_buffer_reserve(priv_dev, buffering + 1,
 					     !!priv_ep->dir);
 	if (ret) {
-- 
2.40.1