On Thu, Aug 29, 2013 at 10:30 AM, Mark Brown [off-list ref] wrote:

On Thu, Aug 29, 2013 at 09:31:55AM -0700, Russ Dill wrote:

quoted

On Thu, Aug 29, 2013 at 8:49 AM, Mark Brown [off-list ref] wrote:

quoted

quoted

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...

quoted

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.

quoted

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.

quoted

quoted

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.

quoted

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.

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