Re: [PATCH] rtc: abx80x: Add support for autocalibration filter capacitor

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Sorry, this was sent prematurely and should have been split into two
patches. It has been resent properly.

On Sat, May 30, 2020 at 8:32 AM Kevin P. Fleming <kevin+linux@xxxxxxx> wrote:
>
> All of the parts supported by this driver can make use of a
> small capacitor to improve the accuracy of the autocalibration
> process for their RC oscillators. If a capacitor is connected,
> a configuration register must be set to enable its use, so a
> new Device Tree property has been added for that purpose.
>
> Signed-off-by: Kevin P. Fleming <kevin+linux@xxxxxxx>
> Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
> Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> To: linux-rtc@xxxxxxxxxxxxxxx
> To: devicetree@xxxxxxxxxxxxxxx
> ---
>  .../bindings/rtc/abracon,abx80x.txt           |  6 ++++
>  drivers/rtc/rtc-abx80x.c                      | 34 +++++++++++++++++++
>  2 files changed, 40 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
> index 2405e35a1bc0..ad5d59ed6f24 100644
> --- a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
> +++ b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
> @@ -29,3 +29,9 @@ and valid to enable charging:
>   - "abracon,tc-diode": should be "standard" (0.6V) or "schottky" (0.3V)
>   - "abracon,tc-resistor": should be <0>, <3>, <6> or <11>. 0 disables the output
>                            resistor, the other values are in kOhm.
> +
> +All of the devices can have a 47pf capacitor attached to increase the
> +autocalibration accuracy of their RC oscillators. To enable usage of the
> +capacitor the following property has to be defined:
> +
> + - "abracon,autocal-filter"
> diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
> index 3521d8e8dc38..be5a814e8c0b 100644
> --- a/drivers/rtc/rtc-abx80x.c
> +++ b/drivers/rtc/rtc-abx80x.c
> @@ -76,6 +76,9 @@
>  #define ABX8XX_CFG_KEY_OSC     0xa1
>  #define ABX8XX_CFG_KEY_MISC    0x9d
>
> +#define ABX8XX_REG_AFCTRL      0x26
> +#define ABX8XX_AUTOCAL_FILTER_ENABLE   0xa0
> +
>  #define ABX8XX_REG_ID0         0x28
>
>  #define ABX8XX_REG_OUT_CTRL    0x30
> @@ -130,6 +133,31 @@ static int abx80x_is_rc_mode(struct i2c_client *client)
>         return (flags & ABX8XX_OSS_OMODE) ? 1 : 0;
>  }
>
> +static int abx80x_enable_autocal_filter(struct i2c_client *client)
> +{
> +       int err;
> +
> +       /*
> +        * Write the configuration key register to enable access to the AFCTRL
> +        * register
> +        */
> +       err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
> +                                       ABX8XX_CFG_KEY_MISC);
> +       if (err < 0) {
> +               dev_err(&client->dev, "Unable to write configuration key\n");
> +               return -EIO;
> +       }
> +
> +       err = i2c_smbus_write_byte_data(client, ABX8XX_REG_AFCTRL,
> +                                       ABX8XX_AUTOCAL_FILTER_ENABLE);
> +       if (err < 0) {
> +               dev_err(&client->dev, "Unable to write autocal filter register\n");
> +               return -EIO;
> +       }
> +
> +       return 0;
> +}
> +
>  static int abx80x_enable_trickle_charger(struct i2c_client *client,
>                                          u8 trickle_cfg)
>  {
> @@ -825,6 +853,12 @@ static int abx80x_probe(struct i2c_client *client,
>                         return err;
>         }
>
> +       if (of_property_read_bool(np, "abracon,autocal_filter")) {
> +               err = abx80x_enable_autocal_filter(client);
> +               if (err)
> +                       return err;
> +       }
> +
>         if (client->irq > 0) {
>                 dev_info(&client->dev, "IRQ %d supplied\n", client->irq);
>                 err = devm_request_threaded_irq(&client->dev, client->irq, NULL,
> --
> 2.26.2
>



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