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

Andrej Picej
2023-06-08T10:35:28Z

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
>>
>