linux-kernel - Re: [PATCH] rtc: rv3028: Improve trickle charger logic

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Date:   Thu, 8 Jun 2023 11:31:55 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Andrej Picej <andrej.picej@...ik.com>
Cc:     a.zummo@...ertech.it, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, upstream@...tec.de
Subject: Re: [PATCH] rtc: rv3028: Improve trickle charger logic

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.

> +	} 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
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com