On Thu, 24 May 2007 06:52:13 -0400
Jeff Garzik [off-list ref] wrote:

Alan Cox wrote:

quoted

quoted

Currently libata does the 400ns thingy in the inline ata_pause() which
unconditionally does ata_altstatus(); ndelay(400); (and thus does it on
PIO, MMIO, anything ...).

It might actually improve performance for PATA if we did as we'll get rid
of an excess (expensive) PCI read access for non MMIO cases.

The spec says you should read AltStatus.  I am definitely not inclined 
to change that part.

Which spec says that and where ?