On Fri, Apr 06, 2012 at 05:35:46PM +0200, Daniel Lezcano wrote: > On 04/06/2012 12:32 PM, Shilimkar, Santosh wrote: > > Peter, > > > > On Thu, Apr 5, 2012 at 7:07 PM, Arjan van de Ven<arjan@xxxxxxxxxxxxxxx> wrote: > >> On 4/5/2012 2:53 AM, Peter De Schrijver wrote: > >>> This patch doesn't update all cpuidle device registrations. I will do that > >> > >> question is if you want to do per cpu latencies, or if you want to have > >> both types of C state in one big table, and have each of the tegra cpyu > >> types pick half of them... > >> > >> > > Indeed !! That should work. > > I thought the C-states are always per CPU based and during the > > cpuidle registration you can register C-state accordingly based on the > > specific CPU types with different latencies if needed. > > > > Am I missing something ? > > That was the case before the cpuidle_state were moved from the > cpuidle_device to the cpuidle_driver structure [1]. > > That had the benefit of using a single latencies array instead of > multiple copy of the same array, which was the case until today. > > I looked at the white paper for the tegra3 and understand this is no > longer true because of the 4-plus-1 architecture [2]. > The reason is not so much 4-plus-1, but in 4 CPU mode, only CPUs 1 - 3 can be powergated individually. To turn off CPU0, the external regulator for the entire cluster is turned off. This means latencies for CPU0 are different from the other CPUs. > With the increasing number of SoCs, we have a lot of new cpuidle drivers > and each time we modify something in the cpuidle core, that impacts all > the cpuidle drivers. > > My feeling is we are going back and forth when patching the cpuidle core > and may be it is time to define a clear semantic before patching again > the cpuidle, no ? > > What could nice is to have: > > * in case of the same latencies for all cpus, use a single array > > * in case of different latencies, group the same latencies into a > single array (I assume this is the case for 4-plus-1, right ?) > > May be we can move the cpuidle_state to a per_cpu pointer like > cpuidle_devices in cpuidle.c and then add: > > register_latencies(struct cpuidle_latencies l, int cpu); > > If we have the same latencies for all the cpus, then we can register the > same array, which is only a pointer. Maybe we also want to make the 'disabled' flag per CPU then or provide some other way the number of C states can be different per CPU? Cheers, Peter. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
