Re: 2.6.32: Promise UDMA33 card refuses to work in UDMA mode

[Jeff Garzik <jeff@garzik.org>]

On 01/05/2010 06:25 AM, Alan Cox wrote:
>> Indeed, which is why I suspect that a global change to handle this
>> controller may not be a good idea. Overriding sff_exec_command for this
>> driver to not do the altstatus read (just wait 600ns, maybe) might be
>> the best solution for now.
>
> Old IDE does 400nS and no read. We know that works. At least for all the
> standard PATA controllers. Thats an incredibly strong argument for doing
> command issue that way for non MMIO controllers.

To which old-IDE do you refer?  :)  This specific area of functionality 
varies from 2.4.x to 2.6.x.  Old-Old-IDE even picks and chooses whether 
or not to wait depending on protocol (PIO or not), something that has 
changed in the more recent old-IDE code.


> The MMIO case is muddy and probably simply does not matter because no
> sane hardware implementation is not going to handle it internally.

It's not muddy, the rules for MMIO are quite clear, as is kernel 
practice for drivers driving MMIO-based hardware.

Any PATA MMIO controller on a PCI card -- pata_pdc2027x comes to mind -- 
must handle this situation, because the PCI posting situation varies 
depending on where you slot in your PCI card.  That's not something a 
controller can really handle internally.

	Jeff