Re: [PATCH 2/3] scsi: add hooks for host runtime power management

[Alan Stern]

On Thu, 3 Nov 2011, Tejun Heo wrote:

> Hello,
> 
> On Thu, Nov 3, 2011 at 8:39 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> >> I don't know. I haven't really thought about it but as it's currently
> >> designed, I don't think it'll be possible to avoid going through EH to
> >> put ATA ports into suspend mode.
> >
> > Why not?
> 
> It's just how things are designed now.  There's no reason why it's
> fundamentally impossible but going around that would require some
> amount of hackery or preferably re-design.  Synchronization against
> command processing, interrupts and all are built around EH.

Then it sounds like the best idea is something like what Ming proposed 
earlier: Have the error handler make some sort of test to determine 
whether it has been invoked for suspend/resume handling, and skip the 
runtime-PM calls on the host if it has.

This new test, whatever it is, should apply both to system suspend and 
runtime suspend.  By the way, what would happen if a system suspend 
occurred while the ATA port was already runtime-suspended?

Alan Stern

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