[PATCH v5] usb: gadget: f_uac2: fix superspeed transfer

[Jack Pham]

From: Jing Leng <jleng@xxxxxxxxxxxxx>

On page 362 of the USB3.2 specification (
https://usb.org/sites/default/files/usb_32_20210125.zip),
The 'SuperSpeed Endpoint Companion Descriptor' shall only be returned
by Enhanced SuperSpeed devices that are operating at Gen X speed.
Each endpoint described in an interface is followed by a 'SuperSpeed
Endpoint Companion Descriptor'.

If users use SuperSpeed UDC, host can't recognize the device if endpoint
doesn't have 'SuperSpeed Endpoint Companion Descriptor' followed.

Currently in the uac2 driver code:
1. ss_epout_desc_comp follows ss_epout_desc;
2. ss_epin_fback_desc_comp follows ss_epin_fback_desc;
3. ss_epin_desc_comp follows ss_epin_desc;
4. Only ss_ep_int_desc endpoint doesn't have 'SuperSpeed Endpoint
Companion Descriptor' followed, so we should add it.

Fixes: eaf6cbe09920 ("usb: gadget: f_uac2: add volume and mute support")
Signed-off-by: Jing Leng <jleng@xxxxxxxxxxxxx>
Signed-off-by: Jack Pham <quic_jackp@xxxxxxxxxxx>
---
v5: Revived from https://lore.kernel.org/linux-usb/20220218095948.4077-1-3090101217@xxxxxxxxxx/
    and rebased on Greg's usb-linus

ChangeLog v3->v4:
- Add "Fixes:" tag in the changelog area
ChangeLog v2->v3:
- Remove static variables which are explicitly initialized to 0
- Remove redundant modification "case USB_SPEED_SUPER_PLUS:"
ChangeLog v1->v2:
- Update more detailed description of the PATCH

 drivers/usb/gadget/function/f_uac2.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 1905a8d8e0c9..08726e4c68a5 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -291,6 +291,12 @@ static struct usb_endpoint_descriptor ss_ep_int_desc = {
 	.bInterval = 4,
 };
 
+static struct usb_ss_ep_comp_descriptor ss_ep_int_desc_comp = {
+	.bLength = sizeof(ss_ep_int_desc_comp),
+	.bDescriptorType = USB_DT_SS_ENDPOINT_COMP,
+	.wBytesPerInterval = cpu_to_le16(6),
+};
+
 /* Audio Streaming OUT Interface - Alt0 */
 static struct usb_interface_descriptor std_as_out_if0_desc = {
 	.bLength = sizeof std_as_out_if0_desc,
@@ -604,7 +610,8 @@ static struct usb_descriptor_header *ss_audio_desc[] = {
 	(struct usb_descriptor_header *)&in_feature_unit_desc,
 	(struct usb_descriptor_header *)&io_out_ot_desc,
 
-  (struct usb_descriptor_header *)&ss_ep_int_desc,
+	(struct usb_descriptor_header *)&ss_ep_int_desc,
+	(struct usb_descriptor_header *)&ss_ep_int_desc_comp,
 
 	(struct usb_descriptor_header *)&std_as_out_if0_desc,
 	(struct usb_descriptor_header *)&std_as_out_if1_desc,
@@ -800,6 +807,7 @@ static void setup_headers(struct f_uac2_opts *opts,
 	struct usb_ss_ep_comp_descriptor *epout_desc_comp = NULL;
 	struct usb_ss_ep_comp_descriptor *epin_desc_comp = NULL;
 	struct usb_ss_ep_comp_descriptor *epin_fback_desc_comp = NULL;
+	struct usb_ss_ep_comp_descriptor *ep_int_desc_comp = NULL;
 	struct usb_endpoint_descriptor *epout_desc;
 	struct usb_endpoint_descriptor *epin_desc;
 	struct usb_endpoint_descriptor *epin_fback_desc;
@@ -827,6 +835,7 @@ static void setup_headers(struct f_uac2_opts *opts,
 		epin_fback_desc = &ss_epin_fback_desc;
 		epin_fback_desc_comp = &ss_epin_fback_desc_comp;
 		ep_int_desc = &ss_ep_int_desc;
+		ep_int_desc_comp = &ss_ep_int_desc_comp;
 	}
 
 	i = 0;
@@ -855,8 +864,11 @@ static void setup_headers(struct f_uac2_opts *opts,
 	if (EPOUT_EN(opts))
 		headers[i++] = USBDHDR(&io_out_ot_desc);
 
-	if (FUOUT_EN(opts) || FUIN_EN(opts))
+	if (FUOUT_EN(opts) || FUIN_EN(opts)) {
 		headers[i++] = USBDHDR(ep_int_desc);
+		if (ep_int_desc_comp)
+			headers[i++] = USBDHDR(ep_int_desc_comp);
+	}
 
 	if (EPOUT_EN(opts)) {
 		headers[i++] = USBDHDR(&std_as_out_if0_desc);
-- 
2.24.0