linux-kernel - Re: [PATCH v3 3/5] power: supply: max17040: Config alert SOC low level threshold from FDT

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Date:   Wed, 29 May 2019 16:46:07 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Matheus Castello <matheus@...tello.eng.br>
Cc:     sre@...nel.org, robh+dt@...nel.org, mark.rutland@....com,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>, lee.jones@...aro.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] power: supply: max17040: Config alert SOC low
 level threshold from FDT

On Mon, 27 May 2019 at 04:46, Matheus Castello <matheus@...tello.eng.br> wrote:
>
> For configuration of fuel gauge alert for a low level state of charge
> interrupt we add a function to config level threshold and a device tree
> binding property to set it in flatned device tree node.
>
> Now we can use "maxim,alert-low-soc-level" property with the values from
> 1% up to 32% to configure alert interrupt threshold.
>
> Signed-off-by: Matheus Castello <matheus@...tello.eng.br>
> ---
>  drivers/power/supply/max17040_battery.c | 52 +++++++++++++++++++++++--
>  1 file changed, 49 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/power/supply/max17040_battery.c b/drivers/power/supply/max17040_battery.c
> index b7433e9ca7c2..2f4851608cfe 100644
> --- a/drivers/power/supply/max17040_battery.c
> +++ b/drivers/power/supply/max17040_battery.c
> @@ -29,6 +29,9 @@
>  #define MAX17040_DELAY         1000
>  #define MAX17040_BATTERY_FULL  95
>
> +#define MAX17040_ATHD_MASK             0xFFC0
> +#define MAX17040_ATHD_DEFAULT_POWER_UP 4
> +
>  struct max17040_chip {
>         struct i2c_client               *client;
>         struct delayed_work             work;
> @@ -43,6 +46,8 @@ struct max17040_chip {
>         int soc;
>         /* State Of Charge */
>         int status;
> +       /* Low alert threshold from 32% to 1% of the State of Charge */
> +       u32 low_soc_alert_threshold;
>  };
>
>  static int max17040_get_property(struct power_supply *psy,
> @@ -99,6 +104,28 @@ static void max17040_reset(struct i2c_client *client)
>         max17040_write_reg(client, MAX17040_CMD, 0x0054);
>  }
>
> +static int max17040_set_low_soc_threshold_alert(struct i2c_client *client,
> +       u32 level)
> +{
> +       int ret;
> +       u16 data;
> +
> +       /* check if level is between 1% and 32% */
> +       if (level > 0 && level < 33) {
> +               level = 32 - level;
> +               data = max17040_read_reg(client, MAX17040_RCOMP);
> +               /* clear the alrt bit and set LSb 5 bits */
> +               data &= MAX17040_ATHD_MASK;
> +               data |= level;
> +               max17040_write_reg(client, MAX17040_RCOMP, data);
> +               ret = 0;
> +       } else {
> +               ret = -EINVAL;
> +       }

This is unusual way of handling error... when you parse DTS, you
accept any value for "level" (even incorrect one). You validate the
value later when setting it and show an error... however you ignore
the error of max17040_write_reg() here... This is correct but looks
unusual.

Best regards,
Krzysztof