usb: ch9: fix up MaxStreams helper

According to USB 3.0 Specification Table 9-22, if
bmAttributes [4:0] are set to zero, it means "no
streams supported", but the way this helper was
defined on Linux, we will *always* have one stream
which might cause several problems.

For example on DWC3, we would tell the controller
endpoint has streams enabled and yet start transfers
with Stream ID set to 0, which would goof up the host
side.

While doing that, convert the macro to an inline
function due to the different checks we now need.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/dwc3/gadget.c

@@ -297,8 +297,7 @@ static int dwc3_gadget_set_ep_config(struct dwc3 *dwc, struct dwc3_ep *dep,
 	params.param1 = DWC3_DEPCFG_XFER_COMPLETE_EN
 		| DWC3_DEPCFG_XFER_NOT_READY_EN;
 
-	if (comp_desc && USB_SS_MAX_STREAMS(comp_desc->bmAttributes)
-			&& usb_endpoint_xfer_bulk(desc)) {
+	if (usb_ss_max_streams(comp_desc) && usb_endpoint_xfer_bulk(desc)) {
 		params.param1 |= DWC3_DEPCFG_STREAM_CAPABLE
 			| DWC3_DEPCFG_STREAM_EVENT_EN;
 		dep->stream_capable = true;

drivers/usb/host/xhci.c

@@ -2799,8 +2799,7 @@ static int xhci_calculate_streams_and_bitmask(struct xhci_hcd *xhci,
 		if (ret < 0)
 			return ret;
 
-		max_streams = USB_SS_MAX_STREAMS(
-				eps[i]->ss_ep_comp.bmAttributes);
+		max_streams = usb_ss_max_streams(&eps[i]->ss_ep_comp);
 		if (max_streams < (*num_streams - 1)) {
 			xhci_dbg(xhci, "Ep 0x%x only supports %u stream IDs.\n",
 					eps[i]->desc.bEndpointAddress,

include/linux/usb/ch9.h

@@ -605,8 +605,26 @@ struct usb_ss_ep_comp_descriptor {
 } __attribute__ ((packed));
 
 #define USB_DT_SS_EP_COMP_SIZE		6
+
 /* Bits 4:0 of bmAttributes if this is a bulk endpoint */
-#define USB_SS_MAX_STREAMS(p)		(1 << ((p) & 0x1f))
+static inline int
+usb_ss_max_streams(const struct usb_ss_ep_comp_descriptor *comp)
+{
+	int		max_streams;
+
+	if (!comp)
+		return 0;
+
+	max_streams = comp->bmAttributes & 0x1f;
+
+	if (!max_streams)
+		return 0;
+
+	max_streams = 1 << max_streams;
+
+	return max_streams;
+}
+
 /* Bits 1:0 of bmAttributes if this is an isoc endpoint */
 #define USB_SS_MULT(p)			(1 + ((p) & 0x3))