usb: dwc3: gadget: let us set lower max_speed (b9e51b2b) · Commits · 戴 / test

In some SoCs, dwc3 is implemented as a USB2.0 only core, meaning that it can't ever achieve SuperSpeed. Currect driver always sets gadget.max_speed to USB_SPEED_SUPER unconditionally. This can causes issues to some Host stacks where the host will issue a GetBOS() request and we will reply with a BOS containing Superspeed Capability Descriptor. At least Windows seems to be upset by this fact and prints a warning that we should connect $this device to another port. [ balbi@ti.com : rewrote entire commit, including source code comment to make a lot clearer what the problem is ] Cc: <stable@vger.kernel.org> Signed-off-by:

Ben McCauley <ben.mccauley@garmin.com> Signed-off-by:

Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

+23 −1

Original line number	Diff line number	Diff line
		@@ -2744,11 +2744,33 @@ int dwc3_gadget_init(struct dwc3 *dwc)
		}

		dwc->gadget.ops = &dwc3_gadget_ops;
		dwc->gadget.max_speed = USB_SPEED_SUPER;
		dwc->gadget.speed = USB_SPEED_UNKNOWN;
		dwc->gadget.sg_supported = true;
		dwc->gadget.name = "dwc3-gadget";

		/*
		* FIXME We might be setting max_speed to <SUPER, however versions
		* <2.20a of dwc3 have an issue with metastability (documented
		* elsewhere in this driver) which tells us we can't set max speed to
		* anything lower than SUPER.
		*
		* Because gadget.max_speed is only used by composite.c and function
		* drivers (i.e. it won't go into dwc3's registers) we are allowing this
		* to happen so we avoid sending SuperSpeed Capability descriptor
		* together with our BOS descriptor as that could confuse host into
		* thinking we can handle super speed.
		*
		* Note that, in fact, we won't even support GetBOS requests when speed
		* is less than super speed because we don't have means, yet, to tell
		* composite.c that we are USB 2.0 + LPM ECN.
		*/
		if (dwc->revision < DWC3_REVISION_220A)
		dwc3_trace(trace_dwc3_gadget,
		"Changing max_speed on rev %08x\n",
		dwc->revision);

		dwc->gadget.max_speed = dwc->maximum_speed;

		/*
		* Per databook, DWC3 needs buffer size to be aligned to MaxPacketSize
		* on ep out.

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