From: Ben McCauley <ben.mccauley@xxxxxxxxxx> 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@xxxxxx : rewrote entire commit, including source code comment to make a lot clearer what the problem is ] Signed-off-by: Ben McCauley <ben.mccauley@xxxxxxxxxx> Signed-off-by: Felipe Balbi <balbi@xxxxxx> --- drivers/usb/dwc3/gadget.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 55ba447fdf8b..91035eefbe77 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -2744,12 +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. */ -- 2.6.2 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
