linux-kernel - Re: [PATCH v3 09/14] rtc: pcf2127: set PWRMNG value for PCF2131

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Date:   Sat, 7 Jan 2023 19:36:06 +0100
From:   Bruno Thomsen <bruno.thomsen@...il.com>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v3 09/14] rtc: pcf2127: set PWRMNG value for PCF2131

Den tor. 15. dec. 2022 kl. 16.19 skrev Hugo Villeneuve <hugo@...ovil.com>:
>
> From: Hugo Villeneuve <hvilleneuve@...onoff.com>
>
> Default PWRMNG[2:0] bits are set to 000b for PCF2127/29, but to
> 111b for PCF2131.
>
> Set these bits to 000b to select same mode as PCF2127/29.
>
> Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>

Reviewed-by: Bruno Thomsen <bruno.thomsen@...il.com>

I think it's a good idea[1] but there have been concerns about
setting default values in the past[2]. In case somebody needs
a different behaviour they should add a device tree property.

[1] https://lore.kernel.org/linux-rtc/20190910143945.9364-1-bruno.thomsen@gmail.com/
[2] https://lore.kernel.org/linux-rtc/20191211163354.GC1463890@piout.net/

> ---
>  drivers/rtc/rtc-pcf2127.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> index 68af4d0438b8..241189ee4a05 100644
> --- a/drivers/rtc/rtc-pcf2127.c
> +++ b/drivers/rtc/rtc-pcf2127.c
> @@ -53,6 +53,7 @@
>  #define PCF2127_BIT_CTRL3_BLF                  BIT(2)
>  #define PCF2127_BIT_CTRL3_BF                   BIT(3)
>  #define PCF2127_BIT_CTRL3_BTSE                 BIT(4)
> +#define PCF2127_CTRL3_PWRMNG_MASK              GENMASK(7, 5)
>  /* Control register 4 */
>  #define PCF2131_REG_CTRL4              0x03
>  #define PCF2131_BIT_CTRL4_TSF4                 BIT(4)
> @@ -1129,6 +1130,20 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
>         regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
>                                 PCF2127_BIT_CTRL1_POR_OVRD);
>
> +       /* Make sure PWRMNG[2:0] is set to 000b. This is the default for
> +        * PCF2127/29, but not for PCF2131 (default of 111b).
> +        *
> +        * PWRMNG[2:0]  = 000b:
> +        *   battery switch-over function is enabled in standard mode;
> +        *   battery low detection function is enabled
> +        */
> +       ret = regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL3,
> +                               PCF2127_CTRL3_PWRMNG_MASK);
> +       if (ret < 0) {
> +               dev_err(dev, "PWRMNG config failed\n");
> +               return ret;
> +       }
> +
>         ret = regmap_read(pcf2127->regmap, pcf2127->cfg->reg_clkout, &val);
>         if (ret < 0)
>                 return ret;
> --
> 2.30.2
>