Hi Andrew, On Fri, May 2, 2014 at 11:53 PM, Andrew Bresticker <abrestic@xxxxxxxxxxxx> wrote: >>> + /* >>> + * TODO: Turn off the clusters when all cores in the cluster >>> + * are down to achieve significant power savings. >>> + */ >> >> This comment should actually be located right after the >> "if (exynos_cluster_unused(cluster))" above. That is where the cluster >> control should be applied, assuming it'll be effective only when WFI is >> executed. > > Correct me if I'm wrong Samsung folks, but I thought it was not > possible to apply cluster power control from a CPU within the cluster > being powered down, i.e. a CPU in the other cluster must be the one to > apply the cluster power control to power down the outbound cluster. I was under the same impression until quite recently. However, based on inputs from the hardware team, there are bits available (in the *COMMON_OPTION register) that ensure "ARM_CORE0~3 are turned off earlier and then ARM_COMMON_L2 is turned off finally". This allows us to turn off the cluster from a cpu of the same cluster. We have used these bits in our cluster power down cpuidle state implementation as well. Regards, Abhilash > > -Andrew -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
