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

[Jeff Garzik <jeff@garzik.org>]

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.

The proper solution is to modify the pci_driver::resume code path, to 
resurrect not only the HBA but also the ATA bus.  Currently we have 
ata_pci_device_{suspend,resume}, whose contents is wholly generic to any 
random PCI device.

I would suggest creating pata_pci_device_resume(), which calls 
ata_pci_device_resume(), and then waits for BSY to clear.

Similarly, create sata_pci_device_resume(), which calls 
ata_pci_device_resume() then calls sata_phy_resume().  Additionally, for 
select SATA controllers (sata_mv, others?), it may be wise to wait for 
BSY to clear after the SATA phy has been awakened.

You are quite right that ata_piix is an inappropriate place to do all this.

	Jeff