usb: gadget: dummy_hcd: complete stream support

dummy_hcd provides (alloc|free)_stream() callbacks but there are not
doing anything. The transfer side also lacks matching of streams. This
patch changes this and implements stream allocation / de-allocation
support and proper urb <=> req matching.
The UDC side exposes a limit of 16 streams. DWC3, the only USB3 UDC has
no limitations in this regard except that it _needs_ to know that
streams will be used at the ep_enable time. At the host side, there is
no real limit either: XHCI can allocate any number of streams as long as
it does not run out of memory. The UAS gadget currently requests 16
streams and the UAS host side fallbacks from the requested 256 down to
16 which is fine.
From the UASP point of view (the only specified user), the number of
used streams does not really matter. The only limitation is that the
host may not use a higher stream than the gadget requested and can deal
with.

The dummy stream support has been modelled after current UAS + XHCI +
DWC3 + UASP usage which helps me testing:
- the device announces that each ep supports 16 streams (even it could
more than that).
- the device side looks into Companion descriptor at ep_enable time and
enables them according to it.
- the host side tries to enable the requested number of streams but the
upper limit is the Comanion descriptor. None (zero streams) is an
error condition, less is okay.

Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/dummy_hcd.c

···
 	unsigned			wedged : 1;
 	unsigned			already_seen : 1;
 	unsigned			setup_stage : 1;
+	unsigned			stream_en:1;
 };
 
 struct dummy_request {
···
 
 	struct usb_device		*udev;
 	struct list_head		urbp_list;
+	u32				stream_en_ep;
+	u8				num_stream[30 / 2];
 
 	unsigned			active:1;
 	unsigned			old_active:1;
···
 
 	_ep->maxpacket = max;
 	ep->desc = desc;
+	if (usb_ss_max_streams(_ep->comp_desc)) {
+		if (!usb_endpoint_xfer_bulk(desc)) {
+			dev_err(udc_dev(dum), "Can't enable stream support on "
+					"non-bulk ep %s\n", _ep->name);
+			return -EINVAL;
+		}
+		ep->stream_en = 1;
+	}
 
-	dev_dbg (udc_dev(dum), "enabled %s (ep%d%s-%s) maxpacket %d\n",
+	dev_dbg(udc_dev(dum), "enabled %s (ep%d%s-%s) maxpacket %d stream %s\n",
 		_ep->name,
 		desc->bEndpointAddress & 0x0f,
 		(desc->bEndpointAddress & USB_DIR_IN) ? "in" : "out",
···
 			 val = "ctrl";
 			 break;
 		 }; val; }),
-		max);
+		max, ep->stream_en ? "enabled" : "disabled");
 
 	/* at this point real hardware should be NAKing transfers
 	 * to that endpoint, until a buffer is queued to it.
···
 
 	spin_lock_irqsave (&dum->lock, flags);
 	ep->desc = NULL;
+	ep->stream_en = 0;
 	retval = 0;
 	nuke (dum, ep);
 	spin_unlock_irqrestore (&dum->lock, flags);
···
 
 /*-------------------------------------------------------------------------*/
 
+static unsigned int dummy_get_ep_idx(const struct usb_endpoint_descriptor *desc)
+{
+	unsigned int index;
+
+	index = usb_endpoint_num(desc) << 1;
+	if (usb_endpoint_dir_in(desc))
+		index |= 1;
+	return index;
+}
+
 /* MASTER/HOST SIDE DRIVER
  *
  * this uses the hcd framework to hook up to host side drivers.
···
  * the host with reads from the device, and so on, based on the
  * usb 2.0 rules.
  */
+
+static int dummy_ep_stream_en(struct dummy_hcd *dum_hcd, struct urb *urb)
+{
+	const struct usb_endpoint_descriptor *desc = &urb->ep->desc;
+	u32 index;
+
+	if (!usb_endpoint_xfer_bulk(desc))
+		return 0;
+
+	index = dummy_get_ep_idx(desc);
+	return (1 << index) & dum_hcd->stream_en_ep;
+}
+
+/*
+ * The max stream number is saved as a nibble so for the 30 possible endpoints
+ * we only 15 bytes of memory. Therefore we are limited to max 16 streams (0
+ * means we use only 1 stream). The maximum according to the spec is 16bit so
+ * if the 16 stream limit is about to go, the array size should be incremented
+ * to 30 elements of type u16.
+ */
+static int get_max_streams_for_pipe(struct dummy_hcd *dum_hcd,
+		unsigned int pipe)
+{
+	int max_streams;
+
+	max_streams = dum_hcd->num_stream[usb_pipeendpoint(pipe)];
+	if (usb_pipeout(pipe))
+		max_streams >>= 4;
+	else
+		max_streams &= 0xf;
+	max_streams++;
+	return max_streams;
+}
+
+static void set_max_streams_for_pipe(struct dummy_hcd *dum_hcd,
+		unsigned int pipe, unsigned int streams)
+{
+	int max_streams;
+
+	streams--;
+	max_streams = dum_hcd->num_stream[usb_pipeendpoint(pipe)];
+	if (usb_pipeout(pipe)) {
+		streams <<= 4;
+		max_streams &= 0xf;
+	} else {
+		max_streams &= 0xf0;
+	}
+	max_streams |= streams;
+	dum_hcd->num_stream[usb_pipeendpoint(pipe)] = max_streams;
+}
+
+static int dummy_validate_stream(struct dummy_hcd *dum_hcd, struct urb *urb)
+{
+	unsigned int max_streams;
+	int enabled;
+
+	enabled = dummy_ep_stream_en(dum_hcd, urb);
+	if (!urb->stream_id) {
+		if (enabled)
+			return -EINVAL;
+		return 0;
+	}
+	if (!enabled)
+		return -EINVAL;
+
+	max_streams = get_max_streams_for_pipe(dum_hcd,
+			usb_pipeendpoint(urb->pipe));
+	if (urb->stream_id > max_streams) {
+		dev_err(dummy_dev(dum_hcd), "Stream id %d is out of range.\n",
+				urb->stream_id);
+		BUG();
+		return -EINVAL;
+	}
+	return 0;
+}
 
 static int dummy_urb_enqueue (
 	struct usb_hcd			*hcd,
···
 
 	dum_hcd = hcd_to_dummy_hcd(hcd);
 	spin_lock_irqsave(&dum_hcd->dum->lock, flags);
+
+	rc = dummy_validate_stream(dum_hcd, urb);
+	if (rc) {
+		kfree(urbp);
+		goto done;
+	}
+
 	rc = usb_hcd_link_urb_to_ep(hcd, urb);
 	if (rc) {
 		kfree(urbp);
···
 }
 
 /* transfer up to a frame's worth; caller must own lock */
-static int
-transfer(struct dummy *dum, struct urb *urb, struct dummy_ep *ep, int limit,
-		int *status)
+static int transfer(struct dummy_hcd *dum_hcd, struct urb *urb,
+		struct dummy_ep *ep, int limit, int *status)
 {
+	struct dummy		*dum = dum_hcd->dum;
 	struct dummy_request	*req;
 
 top:
···
 		unsigned	host_len, dev_len, len;
 		int		is_short, to_host;
 		int		rescan = 0;
+
+		if (dummy_ep_stream_en(dum_hcd, urb)) {
+			if ((urb->stream_id != req->req.stream_id))
+				continue;
+		}
 
 		/* 1..N packets of ep->ep.maxpacket each ... the last one
 		 * may be short (including zero length).
···
 		default:
 		treat_control_like_bulk:
 			ep->last_io = jiffies;
-			total = transfer(dum, urb, ep, limit, &status);
+			total = transfer(dum_hcd, urb, ep, limit, &status);
 			break;
 		}
 
···
 	dum_hcd->timer.function = dummy_timer;
 	dum_hcd->timer.data = (unsigned long)dum_hcd;
 	dum_hcd->rh_state = DUMMY_RH_RUNNING;
+	dum_hcd->stream_en_ep = 0;
 	INIT_LIST_HEAD(&dum_hcd->urbp_list);
 	dummy_hcd_to_hcd(dum_hcd)->power_budget = POWER_BUDGET;
 	dummy_hcd_to_hcd(dum_hcd)->state = HC_STATE_RUNNING;
···
 	struct usb_host_endpoint **eps, unsigned int num_eps,
 	unsigned int num_streams, gfp_t mem_flags)
 {
-	if (hcd->speed != HCD_USB3)
-		dev_dbg(dummy_dev(hcd_to_dummy_hcd(hcd)),
-			"%s() - ERROR! Not supported for USB2.0 roothub\n",
-			__func__);
-	return 0;
+	struct dummy_hcd *dum_hcd = hcd_to_dummy_hcd(hcd);
+	unsigned long flags;
+	int max_stream;
+	int ret_streams = num_streams;
+	unsigned int index;
+	unsigned int i;
+
+	if (!num_eps)
+		return -EINVAL;
+
+	spin_lock_irqsave(&dum_hcd->dum->lock, flags);
+	for (i = 0; i < num_eps; i++) {
+		index = dummy_get_ep_idx(&eps[i]->desc);
+		if ((1 << index) & dum_hcd->stream_en_ep) {
+			ret_streams = -EINVAL;
+			goto out;
+		}
+		max_stream = usb_ss_max_streams(&eps[i]->ss_ep_comp);
+		if (!max_stream) {
+			ret_streams = -EINVAL;
+			goto out;
+		}
+		if (max_stream < ret_streams) {
+			dev_dbg(dummy_dev(dum_hcd), "Ep 0x%x only supports %u "
+					"stream IDs.\n",
+					eps[i]->desc.bEndpointAddress,
+					max_stream);
+			ret_streams = max_stream;
+		}
+	}
+
+	for (i = 0; i < num_eps; i++) {
+		index = dummy_get_ep_idx(&eps[i]->desc);
+		dum_hcd->stream_en_ep |= 1 << index;
+		set_max_streams_for_pipe(dum_hcd,
+				usb_endpoint_num(&eps[i]->desc), ret_streams);
+	}
+out:
+	spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
+	return ret_streams;
 }
 
 /* Reverts a group of bulk endpoints back to not using stream IDs. */
···
 	struct usb_host_endpoint **eps, unsigned int num_eps,
 	gfp_t mem_flags)
 {
-	if (hcd->speed != HCD_USB3)
-		dev_dbg(dummy_dev(hcd_to_dummy_hcd(hcd)),
-			"%s() - ERROR! Not supported for USB2.0 roothub\n",
-			__func__);
-	return 0;
+	struct dummy_hcd *dum_hcd = hcd_to_dummy_hcd(hcd);
+	unsigned long flags;
+	int ret;
+	unsigned int index;
+	unsigned int i;
+
+	spin_lock_irqsave(&dum_hcd->dum->lock, flags);
+	for (i = 0; i < num_eps; i++) {
+		index = dummy_get_ep_idx(&eps[i]->desc);
+		if (!((1 << index) & dum_hcd->stream_en_ep)) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	for (i = 0; i < num_eps; i++) {
+		index = dummy_get_ep_idx(&eps[i]->desc);
+		dum_hcd->stream_en_ep &= ~(1 << index);
+		set_max_streams_for_pipe(dum_hcd,
+				usb_endpoint_num(&eps[i]->desc), 0);
+	}
+	ret = 0;
+out:
+	spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
+	return ret;
 }
 
 static struct hc_driver dummy_hcd = {