Messages in this thread | | | Date | Tue, 26 Apr 2005 22:23:02 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH] PCI: Add pci shutdown ability |
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Hi!
> > Well, you can do "half suspend to ram; change your frequency; half > > resume" today, and it should work, but I do not think you'll like the > > speed. > > Indeed. With people running things like cpuspeed daemons to dynamically > scale speed, this is going to be really painful. > Of course, any operation where we have to quiesce DMA is going to mean > we're increasing latency around the scaling operation, but we don't > have to go through all the hoops that are necessary when suspending.
> Thankfully some of the more recent implementations of speed/voltage > scaling don't have this requirement.
Good, because some devices really need DMA. (Won't audio skip, and USB break when you disable DMA? I do not see how cpufreq doing DMA disable can be usefull.)
> > In a ideal world, calling device_suspend(PMSG_FREEZE) gets you exactly > > that, and we'll do our best to make it fast enough. > > > > OTOH it *needs* to switch consoles to text one (because X may be > > running DMA, right?); I do not think you'll like that one. > > That would be insane, and make cpufreq totally useless for anyone > running X, so no. This is one of the reasons the kernel needs to > arbitrate DMA on behalf of X. It just needs someone to do the work.
Yes... But it also looks like a lot of work :-(. Pavel -- Boycott Kodak -- for their patent abuse against Java. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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