Hi On Fri, 9 Jan 2015, Thierry Reding wrote: > On Fri, Jan 09, 2015 at 01:59:07PM +0000, Mark Rutland wrote: > > On Fri, Jan 09, 2015 at 09:49:14AM +0000, Thierry Reding wrote: > > > > > As I understand it the architected timer will be turned off along with > > > the rest of the CPU complex on Tegra. I'm not sure if that's specific to > > > Tegra or something that other SoCs may do as well. > > > > That doesn't sound right to me: the architecture specifies that the > > system counter must be implemented in an always-on power domain. > > > > Note that that only applies to the counter, not the timers (as the > > comparators can be turned off with the CPUs). > > I'll let Paul comment on this, since I don't know the intimate details. I believe Mark's comments are accurate. In Linux terms, when deep CPU power management states are in use, the ARM architected "timer" is useful as a clocksource, but useless as a wakeup source (a clockevent device). Regarding clocksources, my personal view is that the SoC timer IP blocks should be exposed as a clocksource option if the timer IP blocks are present in the hardware. That written, I would expect that most production implementations will use the ARM architected "timer" as the clocksource. - Paul -- 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
