[PATCH v2 6/8] rtc: pcf85063: support loading quartz-load capacitance from device tree

[Sverdlin, Alexander]

On Mon, 2026-05-11 at 14:09 +0200, Alexander Feilke wrote:
> From: Alexander Feilke <alexander.feilke at ew.tq-group.com>
> 
> Use previously ignored quartz-load-femtofarads property from device tree
> to set load capacitance. If missing, leave the device unconfigured
> as a default might have been set. force_cap is left out for now but
> can be retrofitted in the future as there may be different hardware
> without the 12.500pF flag.
> 
> Signed-off-by: Alexander Feilke <alexander.feilke at ew.tq-group.com>

Reviewed-by: Alexander Sverdlin <alexander.sverdlin at siemens.com>

> ---
>  drivers/rtc/pcf85063.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/drivers/rtc/pcf85063.c b/drivers/rtc/pcf85063.c
> index 0b336b8c5ee..107e8b4d4c8 100644
> --- a/drivers/rtc/pcf85063.c
> +++ b/drivers/rtc/pcf85063.c
> @@ -140,6 +140,30 @@ static int pcf85063_write(struct udevice *dev, unsigned int offset,
>  	return dm_i2c_write(dev, offset, buf, len);
>  }
>  
> +static int pcf85063_load_capacitance(struct udevice *dev)
> +{
> +	u32 load = 7000;
> +	u8 reg = 0;
> +
> +	if (ofnode_read_u32(dev_ofnode(dev), "quartz-load-femtofarads", &load))
> +		return 0;
> +
> +	switch (load) {
> +	default:
> +		dev_warn(dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
> +			 load);
> +		fallthrough;
> +	case 7000:
> +		break;
> +	case 12500:
> +		reg = PCF85063_REG_CTRL1_CAP_SEL;
> +		break;
> +	}
> +
> +	return dm_i2c_reg_clrset(dev, PCF85063_REG_CTRL1,
> +				 PCF85063_REG_CTRL1_CAP_SEL, reg);
> +}
> +
>  static const struct rtc_ops pcf85063_rtc_ops = {
>  	.get = pcf85063_get_time,
>  	.set = pcf85063_set_time,
> @@ -150,8 +174,22 @@ static const struct rtc_ops pcf85063_rtc_ops = {
>  
>  static int pcf85063_probe(struct udevice *dev)
>  {
> +	u8 tmp;
> +	int err;
> +
>  	i2c_set_chip_flags(dev, DM_I2C_CHIP_RD_ADDRESS | DM_I2C_CHIP_WR_ADDRESS);
>  
> +	err = dm_i2c_read(dev, PCF85063_REG_SC, &tmp, sizeof(tmp));
> +	if (err) {
> +		dev_err(dev, "RTC chip is not present\n");
> +		return err;
> +	}
> +
> +	err = pcf85063_load_capacitance(dev);
> +	if (err < 0)
> +		dev_warn(dev, "failed to set xtal load capacitance: %d",
> +			 err);
> +
>  	return 0;
>  }
>  

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com