On Fri, Aug 17, 2012 at 02:13:59PM +0100, Tony Lindgren wrote: > * Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [120817 03:11]: > > On Fri, Aug 17, 2012 at 3:35 PM, Catalin Marinas > > <catalin.marinas@xxxxxxx> wrote: > > > > > > On Fri, Aug 17, 2012 at 10:41:10AM +0100, Santosh Shilimkar wrote: > > > > > > > > So you expect all the secondary CPUs to be in wakeup state and probably > > > > looping in WFE for a signal from kernel to boot. There is one issue > > > > with this requirement though. For large CPU system, you need to reset > > > > all the CPUs and hit this waiting loop. This will lead to large inrush > > > > current need at bootup which may be not be supported. To avoid this > > > > issue, secondary CPUs are kept in OFF state and then they are woken > > > > up from kernel one by one whenever they need to be brought into the > > > > system. This requirement should be considered. > > > > > > I agree, this part will be extended. That's one method that we currently > > > support and suitable to the model. > > > > > > The better method is the SMC standardisation that Charles Garcia-Tobin > > > has written (to be made available soon) and was presented at the last > > > Linaro Connect in HK. Given that the CPU power is usually controlled by > > > the secure side, we'll ask for an SMC to be issued for waking up > > > secondary CPUs, so it's up to the secure firmware to write the correct > > > hardware registers. > > > > > Thanks for the information. SMC standardization would indeed help > > to overcome some of these. Will wait for that information before > > next set of questions. > > Yes please. If the SMC is not standardized for most calls at least, > we'll end up with a horrible mess of SoC specific calls like we > currently have. Related to that, the virtualization calls should be > also standardized so we don't end up with multiple different hypervisors > with different calls. The Power State Coordination Interface initial proposal has been published here: http://infocenter.arm.com/help/topic/com.arm.doc.den0022a/index.html (as with other ARM documents, they are public but free registration required). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
