linux-kernel - Re: [PATCH 1/2] power: supply: max17042_battery: Clear status bits in interrupt handler

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Date:   Mon, 13 Sep 2021 15:02:34 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>,
        Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Anton Vorontsov <anton.vorontsov@...aro.org>,
        Ramakrishna Pallala <ramakrishna.pallala@...el.com>,
        Dirk Brandewie <dirk.brandewie@...il.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/2] power: supply: max17042_battery: Clear status bits in
 interrupt handler

On 12/09/2021 22:54, Sebastian Krzyszkowiak wrote:
> The gauge requires us to clear the status bits manually for some alerts
> to be properly dismissed. Previously the IRQ was configured to react only
> on falling edge, which wasn't technically correct (the ALRT line is active
> low), but it had a happy side-effect of preventing interrupt storms
> on uncleared alerts from happening.
> 
> Fixes: 7fbf6b731bca ("power: supply: max17042: Do not enforce (incorrect) interrupt trigger type")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
> ---
>  drivers/power/supply/max17042_battery.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/power/supply/max17042_battery.c b/drivers/power/supply/max17042_battery.c
> index 8dffae76b6a3..c53980c8432a 100644
> --- a/drivers/power/supply/max17042_battery.c
> +++ b/drivers/power/supply/max17042_battery.c
> @@ -876,6 +876,9 @@ static irqreturn_t max17042_thread_handler(int id, void *dev)
>  		max17042_set_soc_threshold(chip, 1);
>  	}
>  
> +	regmap_clear_bits(chip->regmap, MAX17042_STATUS,
> +			  0xFFFF & ~(STATUS_POR_BIT | STATUS_BST_BIT));
> +

Are you sure that this was the reason of interrupt storm? Not incorrect
SoC value (read from register for ModelGauge m3 while not configuring
fuel gauge model).

You should only clear bits which you are awaken for... Have in mind that
in DT-configuration the fuel gauge is most likely broken by missing
configuration. With alert enabled, several other config fields should be
cleared.

Best regards,
Krzysztof