linux-kernel - Re: [PATCH v4 1/2] power: supply: bq24735: add watchdog timer delay support

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Message-ID: <20210927161511.iwu453xceymyviwe@earth.universe>
Date:   Mon, 27 Sep 2021 18:15:11 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Bruno Meneguele <bruno.meneguele@...rtgreen.net>
Cc:     robh+dt@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 1/2] power: supply: bq24735: add watchdog timer delay
 support

Hi,

On Mon, Aug 16, 2021 at 01:52:44PM -0300, Bruno Meneguele wrote:
> The BQ24735 charger allows the user to set the watchdog timer delay between
> two consecutives ChargeCurrent or ChargeVoltage command writes, if the IC
> doesn't receive any command before the timeout happens, the charge is turned
> off.
> 
> This patch adds the support to the user to change the default/POR value with
> four discrete values:
> 
>   0 - disabled
>   1 - enabled, 44 sec
>   2 - enabled, 88 sec
>   3 - enabled, 175 sec (default at POR)
> 
> These are the options supported in the ChargeOptions register bits 13&14.
> 
> Also, this patch make one additional check when poll-interval is set by the
> user: if the interval set is greater than the WDT timeout it'll fail during
> the probe stage, preventing the user to set non-compatible values between
> the two options.
> 
> Signed-off-by: Bruno Meneguele <bruno.meneguele@...rtgreen.net>
> ---
> Changelog:
>   v3 - check wdt_timeout for the maximum and minimum available values 
> 
>  drivers/power/supply/bq24735-charger.c | 54 ++++++++++++++++++++++++++
>  include/linux/power/bq24735-charger.h  |  1 +
>  2 files changed, 55 insertions(+)
> 
> diff --git a/drivers/power/supply/bq24735-charger.c b/drivers/power/supply/bq24735-charger.c
> index 3ce36d09c017..7e8d0c23df9a 100644
> --- a/drivers/power/supply/bq24735-charger.c
> +++ b/drivers/power/supply/bq24735-charger.c
> @@ -45,6 +45,8 @@
>  /* ChargeOptions bits of interest */
>  #define BQ24735_CHARGE_OPT_CHG_DISABLE	(1 << 0)
>  #define BQ24735_CHARGE_OPT_AC_PRESENT	(1 << 4)
> +#define BQ24735_CHARGE_OPT_WDT_OFFSET	13
> +#define BQ24735_CHARGE_OPT_WDT		(3 << BQ24735_CHARGE_OPT_WDT_OFFSET)
>  
>  struct bq24735 {
>  	struct power_supply		*charger;
> @@ -156,6 +158,20 @@ static int bq24735_config_charger(struct bq24735 *charger)
>  		}
>  	}
>  
> +	if (pdata->wdt_timeout >= 0 && pdata->wdt_timeout <= 3) {

wdt_timeout is unsigned and can't be smaller than 0.

> +		value = pdata->wdt_timeout;
> +
> +		ret = bq24735_update_word(charger->client, BQ24735_CHARGE_OPT,
> +					  BQ24735_CHARGE_OPT_WDT,
> +					  (value << BQ24735_CHARGE_OPT_WDT_OFFSET));
> +		if (ret < 0) {
> +			dev_err(&charger->client->dev,
> +				"Failed to write watchdog timer: %d\n",
> +				ret);
> +			return ret;
> +		}
> +	}
> +
>  	return 0;
>  }
>  
> @@ -347,6 +363,23 @@ static struct bq24735_platform *bq24735_parse_dt_data(struct i2c_client *client)
>  	if (!ret)
>  		pdata->input_current = val;
>  
> +	ret = of_property_read_u32(np, "ti,wdt-timeout", &val);
> +	if (!ret) {
> +		if (val >= 0 && val <= 3) {

wdt_timeout is unsigned and can't be smaller than 0.

> +			pdata->wdt_timeout = val;
> +		} else {
> +			dev_warn(&client->dev,
> +				 "Invalid value for ti,wdt-timeout: %d",
> +				 val);
> +		}
> +	} else {
> +		/* Since 0 is a valid value (disabled), set something
> +		 * greater than the maximum limit accepted from the user to
> +		 * represent the "no change" state. */
> +		pdata->wdt_timeout = 4;
> +	}
> +
> +
>  	pdata->ext_control = of_property_read_bool(np, "ti,external-control");
>  
>  	return pdata;
> @@ -476,6 +509,27 @@ static int bq24735_charger_probe(struct i2c_client *client,
>  			return 0;
>  		if (!charger->poll_interval)
>  			return 0;
> +		if (charger->pdata->wdt_timeout > 0) {
> +			int wdt_ms;
> +
> +			switch (charger->pdata->wdt_timeout) {
> +			case 1:
> +				wdt_ms = 44000;
> +				break;
> +			case 2:
> +				wdt_ms = 88000;
> +				break;
> +			case 3:
> +				wdt_ms = 175000;
> +				break;
> +			}

wdt_ms is not initialized when wdt_timeout is not 1-3 resulting in undefined behaviour.
Also please create constants for the magic numbers, e.g.

#define BQ24735_WDT_OFF                 0
#define BQ24735_WDT_44_SEC              1
#define BQ24735_WDT_88_SEC              2
#define BQ24735_WDT_175_SEC             3
#define BQ24735_WDT_INVALID             4

and use them throughout the code.

-- Sebastian

> +
> +			if (charger->poll_interval > wdt_ms) {
> +				dev_err(&client->dev,
> +					"Poll interval greater than WDT timeout\n");
> +				return -EINVAL;
> +			}
> +		}
>  
>  		ret = devm_delayed_work_autocancel(&client->dev, &charger->poll,
>  						   bq24735_poll);
> diff --git a/include/linux/power/bq24735-charger.h b/include/linux/power/bq24735-charger.h
> index 321dd009ce66..ce5a030ca111 100644
> --- a/include/linux/power/bq24735-charger.h
> +++ b/include/linux/power/bq24735-charger.h
> @@ -12,6 +12,7 @@ struct bq24735_platform {
>  	uint32_t charge_current;
>  	uint32_t charge_voltage;
>  	uint32_t input_current;
> +	uint32_t wdt_timeout;
>  
>  	const char *name;
>  
> -- 
> 2.31.1
> 

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