> On Mar 28, 2020, at 10:37 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 27 Mar 2020, John Donnelly wrote:
>
>> Hi,
>>
>> I am seeing this WARNING event with iommu=off when booting a DL380
>> server with a 5.4.17 kernel.
>
> ...
>
>> The end result is this USB port is not configured when
>> dma_direct_map_page() is called and it returns return
>> DMA_MAPPING_ERROR;
>>
>>
>> When I boot the server with iommu=on I don’t see this sequence :
>
> ...
>
>> On an older kernel 5.3. flavor I am not seeing this behavior, and the usbhib devices appear as expected :
>
> I forgot to mention: Since you have one kernel where the WARNING occurs
> and one where it doesn't, you can use bisection to find the commit that
> was responsible for the change in behavior. If you care to go to the
> trouble...
>
> Alan Stern
>
Hi,
I discovered this particular server doesn’t continue probing the ports behind BCM is due to iommu being on.
With “ iommu=on “
USB Initialization stops after the BCM " 3:1.0 hub with 2 ports detected” , but no additional probing is done to discover the other end-points behind 3:1.0 :
[ 9.467008] hub 2-1:1.0: 8 ports detected
[ 9.538361] usb 4-3: new high-speed USB device number 2 using xhci_hcd
[ 9.564504] usb 4-3: New USB device found, idVendor=0424, idProduct=2660, bcdDevice= 8.01
[ 9.580454] usb 4-3: New USB device strings: Mfr=0, Product=0,SerialNumber=0
[ 9.596642] hub 4-3:1.0: USB hub found
[ 9.611040] hub 4-3:1.0: 2 ports detected.
** NO ADDITIONAL DISCOVERY **
2. With intel_iommu=off, the BCM ports are probed after " 3:1.0: 2 ports detected " state:
[ 5.705072] usb 3-1: new full-speed USB device number 2 using uhci_hcd
[ 5.772363] usb 4-3: new high-speed USB device number 2 using xhci_hcd
[ 5.800528] usb 4-3: New USB device found, idVendor=0424, idProduct=2660,bcdDevice= 8.01
[ 5.816439] usb 4-3: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 5.832298] hub 4-3:1.0: USB hub found
[ 5.845786] hub 4-3:1.0: 2 ports detected. <---- AFTER THIS WE CONTINUE TO PROBE
[ 5.889503] usb 3-1: New USB device found, idVendor=03f0, idProduct=7029, bcdDevice= 0.02
[ 5.905380] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 5.920997] usb 3-1: Product: Virtual Keyboard
[ 5.934493] usb 3-1: Manufacturer: BMC
What prompts the discovery to look beyond : "hub 4-3:1.0: 2 ports detected. “ ? Could there some state that needs examined before it continues ? ( I’ve never dealt with USB before on Linux ) .
The end result is the usbhid devices ( kdb and mouse ) are found :
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/15p, 480M
|__ Port 3: Dev 2, If 0, Class=Hub, Driver=hub/2p, 480M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
|__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 1: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/8p, 480M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
Is there a way I can turn on debug messages for the usb driver(s) to increase verbosity during boot since these are build-in modules ?
