linux-kernel - Re: [PATCH 1/3] power: cpcap-battery: Do not issue low signal too frequently

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Message-ID: <20221110155510.tobdbaabjoe7ugvl@mercury.elektranox.org>
Date:   Thu, 10 Nov 2022 16:55:10 +0100
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        tony@...mide.com, philipp@...s.xyz
Subject: Re: [PATCH 1/3] power: cpcap-battery: Do not issue low signal too
 frequently

Hi,

On Sat, Nov 05, 2022 at 01:25:42PM +0200, Ivaylo Dimitrov wrote:
> It seems that low battery irq may be generated tens of times per second,
> leading to userspace being flooded with unnecessary events.
> 
> Fix that by preventing such events being generated more than once every 30
> seconds.
> 
> Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
> ---

Concept looks ok to me, but the code is slightly racy, since the
thread is flushed before the IRQ is disabled in the remove routine.

>  drivers/power/supply/cpcap-battery.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/power/supply/cpcap-battery.c b/drivers/power/supply/cpcap-battery.c
> index 4676560..8869067 100644
> --- a/drivers/power/supply/cpcap-battery.c
> +++ b/drivers/power/supply/cpcap-battery.c
> @@ -137,6 +137,7 @@ struct cpcap_battery_ddata {
>  	struct power_supply *psy;
>  	struct cpcap_battery_config config;
>  	struct cpcap_battery_state_data state[CPCAP_BATTERY_STATE_NR];
> +	struct delayed_work low_irq_work;
>  	u32 cc_lsb;		/* μAms per LSB */
>  	atomic_t active;
>  	int charge_full;
> @@ -914,9 +915,13 @@ static irqreturn_t cpcap_battery_irq_thread(int irq, void *data)
>  		dev_info(ddata->dev, "Coulomb counter calibration done\n");
>  		break;
>  	case CPCAP_BATTERY_IRQ_ACTION_BATTERY_LOW:
> -		if (latest->current_ua >= 0)
> +		if (latest->current_ua >= 0 &&
> +		    !delayed_work_pending((&ddata->low_irq_work))) {
>  			dev_warn(ddata->dev, "Battery low at %imV!\n",
>  				latest->voltage / 1000);
> +			schedule_delayed_work(&ddata->low_irq_work, 30 * HZ);
> +			disable_irq_nosync(d->irq);
> +		}
>  		break;
>  	case CPCAP_BATTERY_IRQ_ACTION_POWEROFF:
>  		if (latest->current_ua >= 0 && latest->voltage <= 3200000) {
> @@ -1087,6 +1092,21 @@ static int cpcap_battery_calibrate(struct cpcap_battery_ddata *ddata)
>  	return error;
>  }
>  
> +static void cpcap_battery_lowbph_enable(struct work_struct *work)
> +{
> +	struct delayed_work *d_work = to_delayed_work(work);
> +	struct cpcap_battery_ddata *ddata = container_of(d_work,
> +			struct cpcap_battery_ddata, low_irq_work);
> +	struct cpcap_interrupt_desc *d;
> +
> +	list_for_each_entry(d, &ddata->irq_list, node) {
> +		if (d->action == CPCAP_BATTERY_IRQ_ACTION_BATTERY_LOW)
> +			break;
> +	}
> +
> +	enable_irq(d->irq);
> +}
> +
>  #ifdef CONFIG_OF
>  static const struct of_device_id cpcap_battery_id_table[] = {
>  	{
> @@ -1118,6 +1138,8 @@ static int cpcap_battery_probe(struct platform_device *pdev)
>  	if (!ddata)
>  		return -ENOMEM;
>  
> +	INIT_DELAYED_WORK(&ddata->low_irq_work, cpcap_battery_lowbph_enable);

use devm_delayed_work_autocancel() and put it directly before
cpcap_battery_init_interrupts().

>  	cpcap_battery_detect_battery_type(ddata);
>  
>  	INIT_LIST_HEAD(&ddata->irq_list);
> @@ -1185,6 +1207,9 @@ static int cpcap_battery_remove(struct platform_device *pdev)
>  	if (error)
>  		dev_err(&pdev->dev, "could not disable: %i\n", error);
>  
> +	/* make sure to call enable_irq() if needed */
> +	flush_delayed_work(&ddata->low_irq_work);

and this can be dropped afterwards.

> +
>  	return 0;
>  }

Thanks,

-- Sebastian

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