usb HC busted?

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

Hi Mathias,

On Thu, Jun 21, 2018 at 02:01:30PM +0300, Mathias Nyman wrote:
> On 21.06.2018 03:53, Sudip Mukherjee wrote:
> > Hi Mathias, Andy,
> > 
> > On Thu, Jun 07, 2018 at 10:40:03AM +0300, Mathias Nyman wrote:
> > > On 06.06.2018 19:45, Sudip Mukherjee wrote:
<snip>
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git dmapool-test
> https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=dmapool-test
> 
> Tested by just leaving the following running for a few days:
> 
> while true; do echo 0 > authorized; sleep 3; echo 1 > authorized; sleep 3; done;
> For some usb device (for example: /sys/bus/usb/devices/1-8)
> 
> Then grep logs for "MATTU dmatest match! "
> 
> Can you share a bit more details on the platform you are using, and what types of test you are running.

Sorry for the delayed reply, I was in Tokyo for the OSS.

It is a board based on "Intel(R) Atom(TM) CPU  E3840  @ 1.91GHz".
The usb device in question is a bluetooth device:

Bus 001 Device 012: ID 8087:07dc Intel Corp.
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          224 Wireless
  bDeviceSubClass         1 Radio Frequency
  bDeviceProtocol         1 Bluetooth
  bMaxPacketSize0        64
  idVendor           0x8087 Intel Corp.
  idProduct          0x07dc
  bcdDevice            0.01
  iManufacturer           0
  iProduct                0
  iSerial                 0
  bNumConfigurations      1

And the problem that we are seeing is with phone calls via bluetooth.

> Does my test above trigger the case? (show "MATTU dmatest match!")

I have kept it for tonight, will see the results tomorrow morning.
And I am using that same device in the usb script to change "authrized".

But looking at the code for dma_pool_alloc(), it seems 'dma' can have
same value again only if "*(int *)(page->vaddr + offset)" gets a value
of 0 in pool_initialise_page(). But I can't think of anyway how it
can be 0. I have also added some more debugs in the kernel to see what
might be going wrong there.
---
Regards
Sudip
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