On Thu, Aug 29, 2013 at 10:30 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Thu, Aug 29, 2013 at 09:31:55AM -0700, Russ Dill wrote: >> On Thu, Aug 29, 2013 at 8:49 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> > Why does it have to happen this late and are the sequences definitely >> > fixed ones not ones that could depend on the system state at the time >> > we suspend? It'd help to know what exactly is being controlled here... > >> On all am335x platforms, the lower operating point for core voltage >> cannot be reached without first disabling the DDR controller, and >> programming it into a lower power mode. For DDR3 platforms, no such >> lower power mode is available and the lower operating point for core >> voltage can only be reached with the memory controller disabled. > > So this is done from cpuidle rather than system suspend. It is done for system suspend. It isn't possible to do this in a cpuidle use case as the memory controller would need to come out of idle automatically to service DMA requests. >> It certainly is possible that some bizarre I2C regulator may mix in >> regulator voltage and some other state into one I2C register. In the >> case of such a platform, setting the lower operating point would not >> be supported. > > This isn't particularly bizzare, there is no technical reason why a > register in the PMIC has to be given over completely to setting the > voltage and indeed there are PMICs in mainline right now which don't do > that - if you've got 16 bit registers it's probably not going to take > the entire 16 bits to encode the voltage range. > >> > Surely specifying things in terms of the actual sequence would be better >> > than trying to specify the I2C commands if you want this to be done from >> > Linux? If the firmware has to cope directly then this would require the >> > firmware to understand what it's doing of course. > >> I'm not sure what you mean by "actual sequence". Maybe if I show you a >> couple examples, it will be more clear: > > I mean describe the intended sequence of events in the system rather > than the raw register commands to accomplish them. I'm still not sure what you mean. > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- 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
