2013-03-27 00:15:28

by Axel Lin

Subject: regulator: ab8500: ambiguous meaning of delay setting in struct ab8500_regulator_info

Hi,

The comment of struct ab8500_regulator_info says the delay means
"startup/set voltage delay in us".
I'm confused by the meaning, does it mean enable_time or set_voltage_time_sel
time or both?

* @enable_time: Time taken for the regulator voltage output voltage to
* stabilise after being enabled, in microseconds.

* @set_voltage_time_sel: Time taken for the regulator voltage output voltage
* to stabilise after being set to a new value, in microseconds.
* The function provides the from and to voltage selector, the
* function should return the worst case.

Current code only has delay setting for AB8500_LDO_TVOUT, it looks like it
means enable_time rather than the delay for set_voltage_time_sel.
(well, AB8500_LDO_TVOUT is fixed voltage, it does not implement set_voltage_time_sel)

ab8500_regulator_set_voltage_time_sel() returns info->delay, but all it's users
(AB8500_LDO_AUX1, AB8500_LDO_AUX2, AB8500_LDO_AUX3, AB8500_LDO_INTCORE)
do not has delay setting. ( So now ab8500_regulator_set_voltage_time_sel returns 0. )

Axel

2013-03-27 07:58:57

by Bengt Jönsson

Subject: Re: regulator: ab8500: ambiguous meaning of delay setting in struct ab8500_regulator_info

On 03/27/2013 01:15 AM, Axel Lin wrote:
> Hi,
>
> The comment of struct ab8500_regulator_info says the delay means
> "startup/set voltage delay in us".
> I'm confused by the meaning, does it mean enable_time or set_voltage_time_sel
> time or both?
>
> * @enable_time: Time taken for the regulator voltage output voltage to
> * stabilise after being enabled, in microseconds.
>
> * @set_voltage_time_sel: Time taken for the regulator voltage output voltage
> * to stabilise after being set to a new value, in microseconds.
> * The function provides the from and to voltage selector, the
> * function should return the worst case.
The data sheet does not specify time delay for voltage selection, only
enable time. So I have assumed the same time for voltage selection.
> Current code only has delay setting for AB8500_LDO_TVOUT, it looks like it
> means enable_time rather than the delay for set_voltage_time_sel.
> (well, AB8500_LDO_TVOUT is fixed voltage, it does not implement set_voltage_time_sel)
>
> ab8500_regulator_set_voltage_time_sel() returns info->delay, but all it's users
> (AB8500_LDO_AUX1, AB8500_LDO_AUX2, AB8500_LDO_AUX3, AB8500_LDO_INTCORE)
> do not has delay setting. ( So now ab8500_regulator_set_voltage_time_sel returns 0. )
This is a flaw in the driver. It should specify delay for all
regulators, not just VTVout.

Worst case enable time from data sheet:
Vana: enable time = 140 us
Vaux1/2: enable time = 200 us
Vaux3: enable time = 450 us
Vintcore: enable time = 750 us
Vamic1/2: enable time = 500 us
Vdmic: enable time = 420 us
VTVout: enable time = 500 us
Vaudio: enable time = 140 us
Vusb: enable time = 150 us
>
> Axel
>
Thanks for looking into it.

Bengt