El Mon, Mar 20, 2017 at 12:06:15PM +0000 Mark Brown ha dit: > On Fri, Mar 17, 2017 at 05:03:30PM -0700, Matthias Kaehlcke wrote: > > > In principle I totally agree with you that consumers should be able > > to enumerate the supported voltages with the existing functions. And > > they can, as long as they already know (or assume) that the regulator > > they are using actually has discrete steps, otherwise they might get > > unexpected results. > > Given the limits of number representation continuous regulators also > have discrete steps, they just have a lot of them (but so do some > regulators we currently say aren't continuous so...). > > > You are right that my case is very specialist, however I think it is > > a general problem that a consumer can't know whether the results of > > _list_voltage(), etc correspond to the regulator itself or to its > > supplies. E.g. a consumer might have a continuous reg which is > > supplied by a discrete reg, in this case _list_voltage() would return > > the steps of the supply reg, which is probably not what most consumers > > expect. > > No, this is doesn't make much sense! Why should we be reporting > properties of the parent regulator when the child regulator is > regulating away all visibility of those properties? I am confused whether you are confirming that the current behavior makes no sense or if you think that what I'm saying is nonsense. > > > > Please see my explication above on why the vctrl driver needs to know > > > > this. > > > > I'm seeing nothing in the above that addresses my question, you don't > > > even seem to have mentioned supplies. > > > Sorry, I really didn't try to evade your question. Does it make more > > sense with the example above? > > No, not at all. I take this as an indication that you don't think my description above is correct. Let's use a real world example then, tested with actual software and hardware. Our regulator is 'ppvar_bigcpu': https://chromium.googlesource.com/chromiumos/third_party/kernel/+/release-R58-9334.B-chromeos-4.4/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi#177 For our test we change the supply to 'pp1200_lpddr' to make sure the supply has at least one voltage and this voltage is within the constraints of 'ppvar_bigcpu'. 'ppvar_bigcpu' is continuous, however _count_voltages(ppvar_bigcpu) returns 1 and _list_voltage(ppvar_bigcpu, 0) returns 1200000, which is precisely the configuration of 'pp1200_lpddr'. I verified this with a 4.10ish kernel (no major changes, zero changes in regulators). > > > What we should be doing for continuous regulators is allowing people to > > > list the supported voltages as they would for other regulators. > > > In the overall regulator context this may make sense, at this point I > > don't really have enough background on the subsystem to have an > > informed opinion. > > > From the vctrl perspective I wouldn't be overly happy, since it > > wouldn't allow to distinguish between continuous and discrete > > supplies, and I still think that handling discrete supplies > > differently is simpler/more efficient. This doesn't mean I argue > > against your proposal if it is deemed the right thing from a subsystem > > perspective. > > If it helps think of a continuous regulator as a discrete regulator with > a base voltage of 0 and steps of 1uV. Thanks, I understood that. What I didn't realize initially is that we can avoid iterating through all the voltages if the regulator has linear steps, which we can determine with regulator_get_linear_step(). With that in mind I don't see concerns from the vctrl perspective. Matthias -- 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
