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SubjectRe: [PATCH v2 5/5] rtc: pcf85063: set xtal load capacitance from DT
On 08/01/2019 19:54:14+0100, Sam Ravnborg wrote:
> Add support for specifying the xtal load capacitance in the DT node.
> The pcf85063 supports xtal load capacitance of 7pF or 12.5pF.
> If the rtc has the wrong configuration the time will
> drift several hours/week.
>
> The driver use the default value 7pF.
>
> The DT may specify either 7000fF or 12500fF.
> (The DT uses femto Farad to avoid decimal numbers).
> Other values are warned and the driver uses the default value.
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Alessandro Zummo <a.zummo@towertech.it>
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: Urs Fässler <urs.fassler@bbv.ch>
> ---
> drivers/rtc/rtc-pcf85063.c | 39 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> diff --git a/drivers/rtc/rtc-pcf85063.c b/drivers/rtc/rtc-pcf85063.c
> index 283c2335b01b..0c0b6030627e 100644
> --- a/drivers/rtc/rtc-pcf85063.c
> +++ b/drivers/rtc/rtc-pcf85063.c
> @@ -27,6 +27,7 @@
> */
>
> #define PCF85063_REG_CTRL1 0x00 /* status */
> +#define PCF85063_REG_CTRL1_CAP_SEL BIT(0)
> #define PCF85063_REG_CTRL1_STOP BIT(5)
> #define PCF85063_REG_CTRL2 0x01
>
> @@ -180,6 +181,39 @@ static const struct rtc_class_ops pcf85063_rtc_ops = {
> .set_time = pcf85063_rtc_set_time
> };
>
> +static int pcf85063_load_capacitance(struct i2c_client *client)
> +{
> + u32 load;
> + int rc;
> + u8 reg;
> +
> + rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
> + if (rc < 0)
> + return rc;
> +
> + reg = rc;
> + load = 7000;
> + of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
> + &load);
> +
> + switch (load) {
> + default:
> + dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
> + load);

Alignment is not correct

> + /* fall through */
> + case 7000:
> + reg &= ~PCF85063_REG_CTRL1_CAP_SEL;
> + break;
> + case 12500:
> + reg |= PCF85063_REG_CTRL1_CAP_SEL;
> + break;
> + }
> +
> + rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);
> +
> + return rc;
> +}
> +
> static int pcf85063_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -197,6 +231,11 @@ static int pcf85063_probe(struct i2c_client *client,
> return err;
> }
>
> + err = pcf85063_load_capacitance(client);
> + if (err < 0)
> + dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
> + err);

This should be using more tabs.

As you can see, I don't have much to add and I'm quite pleased with the
series.

As Rob pointed out, quartz-load-femtofarads should be added in rtc.txt

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

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