On Thu, Dec 04, 2014 at 12:34:28PM +0100, Lucas Stach wrote:
Am Donnerstag, den 04.12.2014, 16:44 +0530 schrieb Viresh Kumar:
- voltage-tolerance: Specify the CPU voltage tolerance in percentage.
This is extremely ill defined. It doesn't say in which direction the tolerance is to be applied. Can you go below or above the OPP specified voltage? For now everyone just assumes that it has to work both ways. Also with this binding the tolerance is applied for all OPPs, where is very much depends on the individual OPP.
Almost all specifications for voltages are done as either min/typ/max or +/- a target voltage.
If you are going to redefine OPPs anyway I would really like to see this property die and rather have a min/max voltage per OPP. That way you can properly express the OPP constraints. Most OPPs will likely allow a much higher voltage than their minimal specified one, except when you go over thermal limits with a high clock/voltage combination.
If you've got a minimum and maximum you also need to specify a target, generally it's going to be better to go for the target voltage which may not be the midpoint and is unlikely to be one of the bounds. I do think it's sensible to have the option of doing both to more closely match datasheets.
- clock-latency: Specify the possible maximum transition latency for clock,
- in unit of nanoseconds.
Why do we need this? This is property of the clock. We should be able to handle this completely internally in the kernel. I don't know if the clock API has something like this right now, but it should be a trivial addition.
Or have it be part of the clock binding at any rate.