On Fri, 2013-08-09 at 03:54 +0800, Stephen Warren wrote: > On 08/07/2013 08:23 PM, Joseph Lo wrote: > > On Thu, 2013-08-08 at 00:46 +0800, Stephen Warren wrote: > .. > >> I still have absolutely no idea why Tegra30 and Tegra114 are different. > >> > >> You mentioned something about this low-level code only manipulating the > >> IDLE state, and the clock driver needing to restore the other 4 states. > >> This raises yet more questions: > >> > >> 1) Do we not need to restore the other 4 states on Tegra30? If not, why > >> not? If we do, presumably Tegra30 (and Tegra20?) need to the syscore_op > >> this patch series adds to Tegra114 only? If we don't, then why does > >> Tegra114 have to restore them? > > > > We need to restore all of them for all Tegra chips. For Tegra20/30, we > > had done it in the tegra_cpu_car_ops.suspend/resume. For Tegra114, the > > patch was here. > > > > The other reason is: > > 1) The PLLX is the main CPU clock source in Tegra20/30. We can restore > > it ASAP to get a better performance. > > 2) For Tegra114, the PLLX is the CPU clock source when CPU runs at low > > rates. When CPU in high rate, it uses DFLL as clock source. So it > > depends on what the clock source of the CPU when it goes into suspend. > > And the DFLL has its own resume code, it needs to be restored before the > > CPU uses it as clock source again. It makes the CPU clock restore > > sequence like this. > > So, we don't yet support the DFLL upstream. Presumably, the CPU is > always running off PLLX on Tegra114 upstream right now. As such, we can > hard-code that into the resume path just like we do on earlier chips, > i.e. using tegra_cpu_car_ops.resume(). > > Once we do get DFLL support, presumably the DFLL resume path can switch > the register from PLLX to DFLL, and we still won't need a custom > syscore_ops. > > Will that work? Hmm. If we can implement DFLL resume code there, that may be work. But I can't confirm right now. I can move them to tegra_cpu_car_ops for now. We can re-visit this later when we get more function to support. Thanks, Joseph -- 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
