On Sat, Jun 24, 2006 at 04:30:43PM +1000, Benjamin Herrenschmidt wrote: > On Fri, 2006-06-23 at 22:18 -0700, Linus Torvalds wrote: > > And the "suspend_late()" thing really is fundamentally different from > > "suspend()". As mentioned several times, splitting suspend() up is what > > allows us to, very specifically, avoid having to shut down the console > > early. I want to be able to do printk() until as late in the game as > > possible, and preferably as early in the game as possible. > > > > And splitting suspend was the way to do that. And when I actually started > > doing that, splitting resume (which is even _better_) actually fell out of > > it automatically - I needed to do that just to handle the nested error > > cases correctly (which I had earlier thought I'd just punt entirely, and > > require that we do errors in the "prepare/save_state" phase only). > > > > In other words, I think that this patch will allow us to resume, say VGA > > early, and reliably, and get a working console by the time we resume USB. > > So your resume_early is equivalent to my pmac specific hack to resume > the fbdev early (except that my hack is really very very very early :) > Before I even bring the L2 cache back, but that's almost a detail. After > all, nothing says the L2 cache couldn't be just another driver with a > suspend and a resume method :) > > However, I do still think that this late/early business is problematic > with "runtime/dynamic" suspend of individual devices or sub-trees > because of the "irq off" requirement of the late round of calls and I'm > not necessarily fan of having drivers split themselves between the 2 > phases. If there is a case where we would be tempted to do that, then I > tend to prefer splitting into 2 drivers instead. The PHY example is a > good one: move the PHY suspend/resume to the new PHY layer and have > proper PHY drivers with their suspend/resume etc... (reminds me I sitll > need to port sungem to that new stuff... ) > > > Now, it does require that PCI buses (and preferably other devices) go to > > D3 only in suspend_late(), and come back in resume_early(), so that VGA is > > reachable. So that _will_ require driver modifications. > > Yes, though doing the PCI busses that way is fair enough provided we > don't get into semaphore/msleep/etc... vs. interrupt off kind of issues. > I really don't think we need irq off for that late phase :) Let's just > quickly look at the reason why you want IRQs off. I think that it's a > way to avoid being hit by requests etc... right ? Yes, and pci_set_power_state() can require msleep(). A suspend_late() and resume_early() pass with interrupts off does cleanup the ugly legacy device problem and gives some new debugging opportunities. However, I agree, it may not be very useful for most modern devices, especially when considering a possible runtime suspend requirement. Thanks, Adam
