From: Mathias Nyman
> Sent: 10 October 2017 15:13
...
> [ 428.409645] print_req_error: I/O error, dev sdb, sector 128
> [ 428.426612] arm-smmu 2b500000.iommu: Unhandled context fault: fsr=0x8,
> iova=0xff0b1000,
> fsynr=0x183, cb=0
>
> a ring segment is 256 TRBS, each *16 bytes, that ring last TRB should be at
> 0xff0b0ff0
>
> If the adm-smmu iova 0xff0b1000 means something is poking that DMA address
> it's ring after that ring.
That could 'just' be the hardware doing a 'readahead' of the ring.
Somewhat annoying if it is doing that across page boundaries.
Although, in that case, the read values wouldn't be used because the
last TRB is a link.
So that shouldn't stop the USB transfer - just gives an annoying error message.
OTOH if the PCIe read completion ends up with an error status it might halt
the ring (or similar).
David
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