Re: [PATCH] SCSI midlayer power management

[Nigel Cunningham <ncunningham@linuxmail.org>]

Hi.

On Thu, 2004-08-12 at 08:48, Nathan Bryant wrote: 
> Just to speculate about what would be required for swsusp: you probably 
> need to be using a SCSI LLD that properly implements pci suspend/resume, 
> which implies you need to make sure the card's DMA state machine is 
> flushed and idle before suspend completes. I've got a patch that fixes 
> this much up for aic7xxx. And my other midlayer-level patch may also 
> help... What happens during resume is interesting. I think maybe the 
> problem is not what the drive is expecting, but what the card's state 
> engine is expecting when it tries to map commands to command buffers in 
> DMA space.  Maybe you need to suspend the LLD from the context of the 
> kernel that is doing the image load, and then resume from the context of 
> the kernel that was just loaded.

I fully agree. That's what I'm doing at the moment; it's been a while
since I looked at swsusp though, so can't say anything about Pavel &
Patrick's implementation.

> >With my 'device tree' code, I'm getting the struct dev of the device
> >we're using via the struct block_device in the swap_info struct.
> >
> Right, though you also need to get the host adapter's struct device, if 
> you're not already doing so, that is. Many IDE host drivers don't bother 
> with suspend/resume callbacks at the pci_driver level, but SCSI needs 
> callbacks because the BIOS usually doesn't handle things for us.

The host adapter isn't in the device's chain of parents?

Nigel 

-- 
Nigel Cunningham
Christian Reformed Church of Tuggeranong
PO Box 1004, Tuggeranong, ACT 2901

Many today claim to be tolerant. But true tolerance can cope with others
being intolerant.