diff options
| author | Ben McCauley <ben.mccauley@garmin.com> | 2015-11-16 19:47:24 +0300 |
|---|---|---|
| committer | Felipe Balbi <balbi@ti.com> | 2015-11-17 20:35:48 +0300 |
| commit | b9e51b2b1fda19143f48d182ed7a2943f21e1ae4 (patch) | |
| tree | 33239cdda81290cbf5c12c3c262209ea52b82ce3 /drivers/usb/dwc3 | |
| parent | 68fe05e2a45181ce02ab2698930b37f20487bd24 (diff) | |
| download | linux-b9e51b2b1fda19143f48d182ed7a2943f21e1ae4.tar.xz | |
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/dwc3')
| -rw-r--r-- | drivers/usb/dwc3/gadget.c | 24 |
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. */ |