[PATCH 2/4] cpufreq: add i.MX5 cpufreq driver

[Viresh Kumar]

On 26 May 2014 18:41, Lucas Stach <l.stach at pengutronix.de> wrote:

Just to mention that I am trying to help you and am not opposing any
change. We can add this field if its really required and I am just trying
to understand your problem and if we can solve it with current code.

> No, setting voltage-tolerance to zero means I don't accept any tolerance
> at all. Though in practice I have a variable tolerance as I just have a
> fixed maximum voltage for the chip.
>
> For example the i.MX53 has a fixed maximum voltage of 1.4V on the cpu
> rail, so for the slowest OPP the acceptable voltage range is 0.8V to
> 1.4V, for the fastest OPP the range is 1.3V to 1.4V.
>
> So if someone connects a fixed 1.3V regulator, I want to still be able
> to use all OPPs, even though the slowest OPP wants 0.8V ideally. If I
> were to use a tolerance I would have to set is to some relatively strict
> value, in order to not exceed the maximum voltage at the highest OPP,
> but this would mean I could not use the slowest OPP because it's out of
> the tolerance range.

I understood the problem now. But I feel there is nothing imx specific here.
It should be a general concern and I want to know how are people
working around it currently.

IOW can we say that you want tolerance to work only on the positive
side? But no tolerance on the -ve side ?

Also, your example dts says that you do have different voltage levels
for each frequency but actually the regulator may only support a
single voltage. i.e. 1.4 volts.

--
viresh