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authorBen McCauley <ben.mccauley@garmin.com>2015-11-16 17:47:24 +0100
committerFelipe Balbi <balbi@ti.com>2015-11-17 18:35:48 +0100
commitb9e51b2b1fda19143f48d182ed7a2943f21e1ae4 (patch)
tree33239cdda81290cbf5c12c3c262209ea52b82ce3 /drivers/usb
parentusb: musb: fix tx fifo flush handling (diff)
downloadlinux-b9e51b2b1fda19143f48d182ed7a2943f21e1ae4.tar.xz
linux-b9e51b2b1fda19143f48d182ed7a2943f21e1ae4.zip
usb: dwc3: gadget: let us set lower max_speed
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>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/dwc3/gadget.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 55ba447fdf8b..e24a01cc98df 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2744,12 +2744,34 @@ 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.
*/