Re: [PATCH] power: supply: sbs-battery: only return health when battery present

[Brian Norris <briannorris@chromium.org>]

On Fri, Aug 16, 2019 at 09:58:42AM +0200, Michael Nosthoff wrote:
> when the battery is set to sbs-mode and  no gpio detection is enabled
> "health" is always returning a value even when the battery is not present.
> All other fields return "not present".
> This leads to a scenario where the driver is constantly switching between
> "present" and "not present" state. This generates a lot of constant
> traffic on the i2c.

That depends on how often you're checking the "health" attribute,
doesn't it? But anyway, the bug is real.

> This commit changes the response of "health" to an error when the battery
> is not responding leading to a consistent "not present" state.

Ack, and thanks for the fix.

> Fixes: 76b16f4cdfb8 ("power: supply: sbs-battery: don't assume
> MANUFACTURER_DATA formats")
> 
> Signed-off-by: Michael Nosthoff <committed@heine.so>
> Cc: Brian Norris <briannorris@chromium.org>
> Cc: <stable@vger.kernel.org>

Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>

> ---
>  drivers/power/supply/sbs-battery.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
> index 2e86cc1e0e35..f8d74e9f7931 100644
> --- a/drivers/power/supply/sbs-battery.c
> +++ b/drivers/power/supply/sbs-battery.c
> @@ -314,17 +314,22 @@ static int sbs_get_battery_presence_and_health(
>  {
>  	int ret;
>  
> -	if (psp == POWER_SUPPLY_PROP_PRESENT) {
> -		/* Dummy command; if it succeeds, battery is present. */
> -		ret = sbs_read_word_data(client, sbs_data[REG_STATUS].addr);
> -		if (ret < 0)
> -			val->intval = 0; /* battery disconnected */
> -		else
> -			val->intval = 1; /* battery present */
> -	} else { /* POWER_SUPPLY_PROP_HEALTH */
> +	/* Dummy command; if it succeeds, battery is present. */
> +	ret = sbs_read_word_data(client, sbs_data[REG_STATUS].addr);
> +
> +	if (ret < 0) { /* battery not present*/
> +		if (psp == POWER_SUPPLY_PROP_PRESENT) {
> +			val->intval = 0;
> +			return 0;

Technically, you don't need the 'return 0' (and if we care about
symmetry: the TI version doesn't), since the caller knows that "not
present" will yield errors. I'm not sure which version makes more sense.

> +		}
> +		return ret;
> +	}
> +
> +	if (psp == POWER_SUPPLY_PROP_PRESENT)
> +		val->intval = 1; /* battery present */
> +	else /* POWER_SUPPLY_PROP_HEALTH */
>  		/* SBS spec doesn't have a general health command. */
>  		val->intval = POWER_SUPPLY_HEALTH_UNKNOWN;
> -	}
>  
>  	return 0;
>  }
> @@ -626,6 +631,8 @@ static int sbs_get_property(struct power_supply *psy,
>  		else
>  			ret = sbs_get_battery_presence_and_health(client, psp,
>  								  val);
> +
> +		/* this can only be true if no gpio is used */
>  		if (psp == POWER_SUPPLY_PROP_PRESENT)
>  			return 0;
>  		break;
> -- 
> 2.20.1
>