Re: [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc()

[Ulf Hansson <ulf.hansson@linaro.org>]

On 19 March 2015 at 12:36, Mark Brown <broonie@kernel.org> wrote:
> On Thu, Mar 19, 2015 at 12:14:11PM +0100, Ulf Hansson wrote:
>
>> Agree. Moreover we need that API to also pick the closest value to
>> target, when trying the range "target->minimum". I also believe it
>
> The implementation *should* do that anyway, it's just not trivial to
> implement in an efficient fashion with the current information we have
> from drivers.

The APIs regulator_count_voltages() and regulator_list_voltage(), are
currently used from the mmc core to find out which voltages that is
supported (with 0.1V granularity). Then that information can be used
when trying to set a new voltage.

But I guess such a wrapper API is out of the question?

Anyway, I get the feeling that we will need to do the same for this case.

>
>> would be good to allow both upper and lower limits to be zero.
>
> The lower limit can be zero already though it isn't clear to me that
> this is useful.  Setting an upper limit of zero seems nonsensical, an
> upper limit that is lower than the lower limit isn't terribly obvious
> and removing the upper limit isn't safe - it means that we'll happily
> oversupply things which is a road to physical damage.

I am not sure I follow here. In the regulator_set_voltage_tol() you
can only specifiy one limit (tolerance?). What Dough proposed was to
add a new API which can have both a low tolerance value and a high
tolerance value.

Kind regards
Uffe