Re: [PATCH] SCSI midlayer power management

Benjamin Herrenschmidt
2004-08-12T23:09:17Z

On Thu, 2004-08-12 at 22:48, James Bottomley wrote:
> On Wed, 2004-08-11 at 19:36, Benjamin Herrenschmidt wrote:
> > Some hosts will continuously DMA to memory iirc.. I remember having a
> > problem with 53c8xx on some macs when transitionning from MacOS to Linux
> > because of that.
>
> I think you're thinking of the scripts engine? on pre 53c875 chips,
> yes, this is true. The on-board processor is executing instructions
> from host memory. However, this is read only in quiescent (waiting for
> host connect or target reconnect) mode, so shouldn't be a problem for
> suspend. On the 875 and later, we host the scripts in on-chip memory so
> they shouldn't be troubling main memory when idling.

The problem was a 875, the script was writing some kind of status or
whatever at regular interval to host memory. Might be specific to the
script used by the MacOS driver tho...

Ben.