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 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.
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