On Sat, 3 Nov 2012 05:26:35 +0100
Borislav Petkov [off-list ref] wrote:

On Wed, Oct 24, 2012 at 11:57:46AM +0100, Alan Cox wrote:

quoted

Which is an ATA layer bug - adev->dma_mode should never be called
without a DMA mode in normal use.

Ok, it looks like this would take a while to fix.

Alan, what is your suggestion for a proper fix, uncomment XFER_PIO_SLOW
and drop to it with a big warning that ACPI is giving botched

No. The proper fix is to find out how it got called with no DMA mode set.
There is no reason ACPI can't return pure PIO answers. If it does however
then the DMA mode setting call should not be made by the core libata
code. Lots of our ATA driver code relies upon that so if it's actually
what is happening that is what needs fixing.

Alan