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SubjectRe: [PATCH] SCSI midlayer power management

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 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.

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