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

From: Nicolas Boichat
Date: Mon Aug 10 2020 - 03:32:33 EST


On Mon, Aug 10, 2020 at 3:02 PM Ikjoon Jang <ikjn@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
> 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
>