Mark Brown wrote: > On Tue, Aug 17, 2010 at 12:33:33PM -0700, Bobby Crabtree wrote: >> Mark Brown wrote: > >>> It's unlikely that the highest voltage would ever be the best choice... > >> We do need the highest voltage. Let's say we have two consumers >> (A and B). Both require 1.3V for "normal" operations. Then let's >> say that consumer A can save power by reducing the voltage to 1.1V >> (but it doesn't require 1.1V). If the core were to immediately apply >> 1.1V, then the 1.3V requirement of consumer B would not be satisfied. > > That's not the highest voltage, that's the minimum voltage that > satisfies all the requests that the consumers have made. The consumer > which requires 1.1V will have requested 1.1V up to, say, 3.3V. The > consumer that requested 1.3V will have requested, say, 1.3-1.8V and > let's say the machine constraints will allow at least these ranges. > 1.3V is the lowest voltage that hits all the constraints, but it's still > lower than any of the maxima. > Aah. I get it now. >>> This was actually a feature of the regulator API when originally >>> proposed, it got dropped for ease of review but there's some remanants >>> of this in the code so it shouldn't be hard to resurrect. Whenever a >>> voltage was set the code stored the range on the consumer then iterated >>> over all consumers applying their ranges plus the machine constraints >>> rather than just using the immediate value. > >> I noticed some of the remnants. But I'm not sure I follow what you >> are saying. What range would the core actually propagate to the >> driver? The minimum min_uV and the maximum max_uV? We need the core >> to propagate the maximum min_uV and the maximum max_uV. > > No, it'd be the maximum min_uV and the minimum max_uV - this is already > happening when the constraints from the machine are applied, it'd just > be applying a wider set of constraints. In principle all we need to do > is remember the voltage constraints that individual consumers set and > then iterate over all the enabled consumers when one of them changes its > range (or is enabled/disabled) instead of just taking the immediate > values from the consumer. Got it. Only remaining question I have is if the aggregation of multiple consumer constraints should be the default (and only) behavior. Or should we introduce a new flag to the regulator_constraints structure that tells the core to aggregate consumer voltages constraints? -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
