linux-kernel - Re: [PATCH] power: supply: sbs-battery: don't assume i2c errors as battery disconnect

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Date:   Mon, 10 Aug 2020 15:32:14 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Ikjoon Jang <ikjn@...omium.org>
Cc:     Sebastian Reichel <sre@...nel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] power: supply: sbs-battery: don't assume i2c errors as
 battery disconnect

On Mon, Aug 10, 2020 at 3:02 PM Ikjoon Jang <ikjn@...omium.org> wrote:
>
> Current sbs-battery considers all smbus errors as diconnection events
> when battery-detect pin isn't supplied, and restored to present state back
> on any successful transaction were made.
>
> This can leads to unlimited state changes between present and !present
> when one unsupported command was requested and other following commands
> were successful, e.g. udev rules tries to read multiple properties.
>
> This patch checks battery presence by reading well-known register to
> check battery existence.
>
> Signed-off-by: Ikjoon Jang <ikjn@...omium.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 73461321eb05..483f814385a3 100644
> --- a/drivers/power/supply/sbs-battery.c
> +++ b/drivers/power/supply/sbs-battery.c
> @@ -875,10 +875,17 @@ static int sbs_get_property(struct power_supply *psy,
>                 return -EINVAL;
>         }
>
> -       if (!chip->gpio_detect &&
> -               chip->is_present != (ret >= 0)) {
> -               sbs_update_presence(chip, (ret >= 0));
> -               power_supply_changed(chip->power_supply);
> +       if (!chip->gpio_detect && chip->is_present != (ret >=0)) {
> +               bool old_present = chip->is_present;
> +               union power_supply_propval val;
> +
> +               ret = sbs_get_battery_presence_and_health(
> +                               client, POWER_SUPPLY_PROP_PRESENT, &val);
> +
> +               sbs_update_presence(chip, !ret && !!(val.intval));

No need for the !!: !ret && val.intval .

> +
> +               if (old_present != chip->is_present)
> +                       power_supply_changed(chip->power_supply);
>         }
>
>  done:
> @@ -1063,11 +1070,11 @@ static int sbs_probe(struct i2c_client *client)
>          * to the battery.
>          */
>         if (!(force_load || chip->gpio_detect)) {
> -               rc = sbs_read_word_data(client, sbs_data[REG_STATUS].addr);
> -
> -               if (rc < 0) {
> -                       dev_err(&client->dev, "%s: Failed to get device status\n",
> -                               __func__);
> +               union power_supply_propval val;
> +               rc = sbs_get_battery_presence_and_health(
> +                               client, POWER_SUPPLY_PROP_PRESENT, &val);
> +               if (rc < 0 || !val.intval) {
> +                       dev_err(&client->dev, "Failed to get present status\n");
>                         goto exit_psupply;

sbs_get_battery_presence_and_health also reads
sbs_data[REG_STATUS].addr. That's good.

However, with psp == POWER_SUPPLY_PROP_PRESENT,
sbs_get_battery_presence_and_health always returns 0, but sets
val.intval = 0 in case of error.

This means that you goto exit_psupply with rc == 0, and sbs_probe does not fail.

I wonder if you should just drop this change, and use
sbs_read_word_data(client, sbs_data[REG_STATUS].addr); above, too.

>                 }
>         }
> --
> 2.28.0.236.gb10cc79966-goog
>