Re: [PATCH] rtc: rv3028: Improve trickle charger logic

[Andrej Picej]

Hi Alexandre,

On 8. 06. 23 11:31, Alexandre Belloni wrote:
> Hello,
>
> On 08/06/2023 11:04:46+0200, Andrej Picej wrote:
> > +	ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &val_old);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* mask out only trickle charger bits */
> > +	val_old = val_old & (RV3028_BACKUP_TCE | RV3028_BACKUP_TCR_MASK);
> > +
> >   	/* setup trickle charger */
> > -	if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
> > -				      &ohms)) {
> > +	if (device_property_read_u32(&client->dev, "trickle-resistor-ohms", &ohms)) {
> > +		/* disable the trickle charger */
> > +		val = 0;
>
> You can't do that, this will break existing users that may set the
> trickle charger from their bootloader for example.

hmm...ok I understand that idea. I thought that might be a problem. I 
guess keeping default as it is has a higher priority.

What do you say if setting this property to 0 (or maybe -1) disabled the 
trickle charger?
So if users add:

trickle-resistor-ohms = <0>;
or
trickle-resistor-ohms = <(-1)>;

this would mean disable the trickle charger?

I know it is far from optimal, but this would solve both things:
* not braking existing implementation,
* users could disable the trickle charger.

What do you say.

Thanks for your review.

Best regards,
Andrej

> > +	} else {
> >   		int i;
> >   
> >   		for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
> > @@ -947,15 +957,21 @@ static int rv3028_probe(struct i2c_client *client)
> >   				break;
> >   
> >   		if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
> > -			ret = rv3028_update_cfg(rv3028, RV3028_BACKUP, RV3028_BACKUP_TCE |
> > -						 RV3028_BACKUP_TCR_MASK, RV3028_BACKUP_TCE | i);
> > -			if (ret)
> > -				return ret;
> > +			/* enable the trickle charger and setup its resistor accordingly */
> > +			val = RV3028_BACKUP_TCE | i;
> >   		} else {
> >   			dev_warn(&client->dev, "invalid trickle resistor value\n");
> >   		}
> >   	}
> >   
> > +	/* only update EEPROM if changes are necessary */
> > +	if (val_old != val) {
> > +		ret = rv3028_update_cfg(rv3028, RV3028_BACKUP, RV3028_BACKUP_TCE |
> > +					RV3028_BACKUP_TCR_MASK, val);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> >   	ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
> >   	if (ret)
> >   		return ret;
> > --
> > 2.25.1