Discussion:
USB problems with Intel Atom E3825
Norbert Koch
2018-07-04 12:52:24 UTC
Permalink
Hello.

We are investigating to switch our embedded product to a
cpu board with an Intel Atom E3825 cpu.

Our external hardware is connected through parallel pci
and contains slow static rams. Access cycles for reading
and writing are at about 1µs.

When we write to our hardware we see a strange phenomenon:
As soon as we continuously write blocks of more than about 24 bytes
we see that usb generates a lot of ERR_STALLED messages according
to usbdump.

FreeBSD identifies an ehci controller. There seems to be no ohci or uhci
controller onboard.

The exact same happens under FreeBSD 10.3 und 11.2, i386 and amd64 kernel.
It never happens when reading the memory even with much bigger
block sizes.
We never saw any problems with older boards and different chipsets.

We contacted the board manufacturer about this and - as we understand -
there obviously are known problems with the cpu's pci bridges.
But they could not confirm that our problem is related.

For testing I downloaded the board manufacturer's embedded linux image
(yocto) and found that linux seems to work fine.
At least I could not find any problems with usb.
So, my idea is that some linux kernel developers know about problems
with that chipset and somehow work around it in kernel code.

Does anyone here have an idea about this? Are there any
kernel switches/options/hints or usb quirks I could possibly try?

Thank you in advance.

Norbert Koch

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