[PATCH 3/5] regulator: allow use of dummy regulator

[Andrej Picej]

On 17. 11. 21 08:21, Sascha Hauer wrote:
> On Mon, Nov 15, 2021 at 02:02:06PM +0100, Andrej Picej wrote:
>> It is quite common for users to delete power supply nodes of regulators
>> which aren't yet supported.
>> The idea of a function call or devicetree property which allows use of
>> dummy regulator is not new. This implementation uses barebox specific
>> devicetree property "barebox,allow-dummy-supply" to allow switching to
>> dummy power regulator.
>> Basically just catch the regulators ensure_probed error, if this
>> property is set.
>>
>> Signed-off-by: Andrej Picej <andrej.picej at norik.com>
>> ---
>>   drivers/regulator/core.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
>> index 097f7d779..1c58932e1 100644
>> --- a/drivers/regulator/core.c
>> +++ b/drivers/regulator/core.c
>> @@ -231,8 +231,15 @@ static struct regulator_internal *of_regulator_get(struct device_d *dev, const c
>>   	}
>>   
>>   	ret = of_device_ensure_probed(node);
>> -	if (ret)
>> +	if (ret) {
>> +		if (of_get_property(dev->device_node, "barebox,allow-dummy-supply", NULL)) {
>> +			dev_dbg(dev, "Allow use of dummy regulator for " \
>> +				"%s-supply\n", supply);
>> +			ri = NULL;
>> +			goto out;
>> +		}
>>   		return ERR_PTR(ret);
> 
> I wonder if we should rather add a property on the producer side than on
> the consumer side, i.e. Add a barebox,status = "disabled" property to
> the regulator node. We had the same discussion with phys recently, maybe
> we can use the same approach for both issues.
> 

I was wandering that too. But decided to go with consumer side so users 
which might want to use this have to enable this for every consumers 
which can use dummy regulators. IMO this would mean more thought would 
go into this and would be consequently more error prone.

So for producer side did you have in mind that this setting will be set 
for every regulator, like this?

>                 regulators {
>                         vddcore_reg: bcore1 {
> +                               barebox,allow-dummy-supply;
>                                 regulator-min-microvolt = <730000>;
>                                 regulator-max-microvolt = <1380000>;
>                                 regulator-always-on;
>                         };

Or should this setting be set for all regulators provided by the same 
IC, like this?

>                 regulators {
> +                       barebox,allow-dummy-supply;
>                         vddcore_reg: bcore1 {
>                                 regulator-min-microvolt = <730000>;
>                                 regulator-max-microvolt = <1380000>;
>                                 regulator-always-on;
>                         };

I guess we could make both cases work, first check if 
"barebox,allow-dummy-supply" is present in the regulator node and then 
also check parent node (regulators)? What do you think?

BR,
Andrej