regulator: Policy for setting current limits

regulator: Policy for setting current limits

[Heiko Stübner]

Hi,

I hit a problem when setting a current limit and am not sure whose fault it is 
(i.e. which component to change). Therefore I'd appreciate a pointer in the 
right direction.

After the recent changes the gpio-regulator always selects the minimal value 
to set. The gpio-vbus driver sets it's current limits as 0 - x mA (x = 100, 
500). Therefore if 500mA are the upper limit but the regulator also supports 
lower values, these lower values always get selected (100mA in my case).
In contrast pda_power sets the target current as both lower and upper limit.

So the question is, what is the correct way to handle this:

(a) let the gpio-regulator select the max current (in contrast to the minimum 
voltage)
(b) change gpio-vbus to also use the target current as min and max value
(c) something else


Thanks
Heiko

Re: regulator: Policy for setting current limits

[Mark Brown]

On Mon, Aug 06, 2012 at 01:27:56AM +0200, Heiko Stübner wrote:

> 500). Therefore if 500mA are the upper limit but the regulator also supports 
> lower values, these lower values always get selected (100mA in my case).
> In contrast pda_power sets the target current as both lower and upper limit.

This isn't good, it means that the regulator has to be able to deliver
exactly the limit requested.

> (a) let the gpio-regulator select the max current (in contrast to the minimum 
> voltage)
> (b) change gpio-vbus to also use the target current as min and max value
> (c) something else

Regulators should be tending to the maximum in the available range and
consumers should specify the widest range possible so both a and b.

Re: regulator: Policy for setting current limits

[Heiko Stübner]

Am Montag, 6. August 2012, 13:56:33 schrieb Mark Brown:
> On Mon, Aug 06, 2012 at 01:27:56AM +0200, Heiko Stübner wrote:
> > 500). Therefore if 500mA are the upper limit but the regulator also
> > supports lower values, these lower values always get selected (100mA in
> > my case). In contrast pda_power sets the target current as both lower
> > and upper limit.
> 
> This isn't good, it means that the regulator has to be able to deliver
> exactly the limit requested.
> 
> > (a) let the gpio-regulator select the max current (in contrast to the
> > minimum voltage)
> > (b) change gpio-vbus to also use the target current as min and max value
> > (c) something else
> 
> Regulators should be tending to the maximum in the available range and
> consumers should specify the widest range possible so both a and b.

Is this true for all regulators (i.e. voltage and currency regulators)?

Because 4dbd8f63f07a (regulator: gpio-regulator: Set the smallest 
voltage/current in the specified range) implemented the exact oposite.

Thanks
Heiko

Re: regulator: Policy for setting current limits

[Mark Brown]

On Tue, Aug 07, 2012 at 01:19:34AM +0200, Heiko Stübner wrote:
> Am Montag, 6. August 2012, 13:56:33 schrieb Mark Brown:

> > Regulators should be tending to the maximum in the available range and
> > consumers should specify the widest range possible so both a and b.

> Is this true for all regulators (i.e. voltage and currency regulators)?

No, voltage regualtors should tend to the lowest voltage.