Not enough bandwidth with Magewell XI100DUSB-HDMI

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 19.01.2018 22:12, Philipp Zabel wrote:
> Hi,
> 
> On Fri, Jan 19, 2018 at 2:10 PM, Michael Tretter
> <m.tretter@pengutronix.de> wrote:
>> I found the old thread and it sounds exactly like my issue. Different
>> camera, but same xHCI controller.
> 
> I have exactly the same issue with the xHCI controller of my laptop and
> "Oculus Sensor" USB3 isochronous mostly-UVC cameras:
> 
> 00:14.0 USB controller: Intel Corporation Wildcat Point-LP USB xHCI
> Controller (rev 03) (prog-if 30 [XHCI])
>      Subsystem: Lenovo Wildcat Point-LP USB xHCI Controller
>      Flags: bus master, medium devsel, latency 0, IRQ 44
>      Memory at f2220000 (64-bit, non-prefetchable) [size=64K]
>      Capabilities: [70] Power Management version 2
>      Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
>      Kernel driver in use: xhci_hcd
>      Kernel modules: xhci_pci
> 
> T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  4 Spd=5000 MxCh= 0
> D:  Ver= 3.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS= 9 #Cfgs=  1
> P:  Vendor=2833 ProdID=0211 Rev= 0.00
> S:  Manufacturer=Oculus VR
> S:  Product=Rift Sensor
> S:  SerialNumber=WMTD3034300BCT
> C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=800mA
> A:  FirstIf#= 0 IfCount= 2 Cls=ff(vend.) Sub=03 Prot=00
> I:* If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=01 Prot=00 Driver=uvcvideo
> E:  Ad=83(I) Atr=03(Int.) MxPS=  32 Ivl=128ms
> I:* If#= 1 Alt= 0 #EPs= 0 Cls=ff(vend.) Sub=02 Prot=00 Driver=uvcvideo
> I:  If#= 1 Alt= 1 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=uvcvideo
> E:  Ad=81(I) Atr=05(Isoc) MxPS=1024 Ivl=125us
> I:  If#= 1 Alt= 2 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=uvcvideo
> E:  Ad=81(I) Atr=05(Isoc) MxPS=1024 Ivl=125us
> 
> Any USB2 or USB3 device that I plug in while the first camera is streaming in
> altsetting 1 or 2 causes the bandwidth error. The same happens when I try to
> change the altsetting on an isochronous endpoint of an already plugged device.
> While the camera is in altsetting 0, other devices can be probed and work.
> 
>> For some tests, I changed the xhci_change_max_exit_latency() function
>> to ignore the requested MEL and set the MEL to 0. Now the USB devices
>> are detected correctly.
> 
> Exactly the same thing helps here, as well. With this hack, streaming from two
> of those cameras at the same time works without any apparent problem:
> 
> ----------8<----------
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 297536c9fd00..3cb4a60d8822 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4025,7 +4025,7 @@ static int __maybe_unused
> xhci_change_max_exit_latency(struct xhci_hcd *xhci,
>          ctrl_ctx->add_flags |= cpu_to_le32(SLOT_FLAG);
>          slot_ctx = xhci_get_slot_ctx(xhci, command->in_ctx);
>          slot_ctx->dev_info2 &= cpu_to_le32(~((u32) MAX_EXIT));
> -       slot_ctx->dev_info2 |= cpu_to_le32(max_exit_latency);
> +       slot_ctx->dev_info2 |= cpu_to_le32(0);
>          slot_ctx->dev_state = 0;
> 
>          xhci_dbg_trace(xhci, trace_xhci_dbg_context_change,
> ---------->8----------
> 

Ok, back after a week on sickleave.
I'm getting the magewell capture device and try to reproduce this myself.

-Mathias
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