Re: [PATCH] Add ata_piix's own resume function

[Jeff Garzik <jeff@garzik.org>]

Jeff Garzik wrote:
> Jens Axboe wrote:
>> On Fri, May 26 2006, zhao, forrest wrote:
>>> For ata_piix resume operation, it first waits for BUSY bit clear,
>>> then calls ata_device_resume().
>>
>> This has the problem that it introduces scsi specific knowledge into
>> ata_piix, something that is both a violation and a problem because we
>> are moving libata away from scsi. I think the best way to currently do
>> this is to introduce a ata_port_ops hook (pre_resume()?) that waits for
>> busy clear and gets called in ata_device_resume is probably the way to
>> go.
> 
> ata_device_resume() is fine as-is.  Modifying it to resurrect the bus is 
> a gross layering violation.  Resume must be done in this order:
> 
>     controller -> bus -> device
> 
> Thus, the bus must be resurrected and brought to a known HSM state (bus 
> idle), and then ata_device_resume() will work just fine.

Additionally, once Tejun's EH stuff is in mainline, the best thing to do 
will be to trigger a revalidate.  With the EH stuff, we can easily 
handle the rare case of waking up and noticing that a different device 
has been plugged in, in addition to the common case.

	Jeff