Re: [PATCH 2/4] hwmon: Add Qualcomm PMIC BCL hardware monitor driver

[Guenter Roeck <linux@roeck-us.net>]

On 3/20/26 07:52, Daniel Lezcano wrote:
> Hi Manaf,
> 
> On Fri, Feb 06, 2026 at 02:44:06AM +0530, Manaf Meethalavalappu Pallikunhi wrote:
>> Add support for Qualcomm PMIC Battery Current Limiting (BCL) hardware
>> monitor driver. The BCL peripheral is present in Qualcomm PMICs and
>> provides real-time monitoring and protection against battery
>> overcurrent and under voltage conditions.
>>
>> The driver monitors:
>> - Battery voltage with configurable low voltage thresholds
>> - Battery current with configurable high current thresholds
>> - Two limit alarm interrupts (max/min, critical)
> 
> Can you describe the behavior of the alarm ?
> 
> I assume the alarm is raised when a threshold is crossed from normal
> to anormal condition leading to a hwmon event.
> 
>   * Does the BCL trigger an interrupt when going back to the normal condition ?
> 
>   * When is the alarm flag reset ?
> 
>   * Can we have a flood of events if the current / voltage is wavering
>     around the thresholds ?
> 
> Overall, the driver is too big, so hard to review. It is better to
> provide a simplified version with one version supported.
> 
>> The driver integrates with the Linux hwmon subsystem and provides
>> standard hwmon attributes for monitoring battery conditions.
>>
>> Signed-off-by: Manaf Meethalavalappu Pallikunhi <manaf.pallikunhi@oss.qualcomm.com>
>> ---
>>   MAINTAINERS                    |   9 +
>>   drivers/hwmon/Kconfig          |   9 +
>>   drivers/hwmon/Makefile         |   1 +
>>   drivers/hwmon/qcom-bcl-hwmon.c | 982 +++++++++++++++++++++++++++++++++++++++++
>>   drivers/hwmon/qcom-bcl-hwmon.h | 311 +++++++++++++
>>   5 files changed, 1312 insertions(+)
> 
> [ ... ]
> 
>> diff --git a/drivers/hwmon/qcom-bcl-hwmon.c b/drivers/hwmon/qcom-bcl-hwmon.c
>> new file mode 100644
>> index 000000000000..a7e3b865de5c
>> --- /dev/null
>> +++ b/drivers/hwmon/qcom-bcl-hwmon.c
>> @@ -0,0 +1,982 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Qualcomm pmic BCL hardware driver for battery overcurrent and
>> + * battery or system under voltage monitor
>> + *
>> + * Copyright (c) 2026, Qualcomm Innovation Center, Inc. All rights reserved.
>> + */
> 
> Old copyright format
> 
>> +#include <linux/devm-helpers.h>
>> +#include <linux/err.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/mutex.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/property.h>
>> +#include <linux/regmap.h>
>> +#include <linux/workqueue.h>
>> +
>> +#include "qcom-bcl-hwmon.h"
>> +
>> +ADD_BCL_HWMON_ALARM_MAPS(in, min, lcrit);
>> +ADD_BCL_HWMON_ALARM_MAPS(curr, max, crit);
>> +
>> +/* Interrupt names for each alarm level */
>> +static const char * const bcl_int_names[ALARM_MAX] = {
>> +	[LVL0] = "bcl-max-min",
>> +	[LVL1] = "bcl-critical",
>> +};
> 
> IIUC there are three levels of alarms but the hwmon only has max/min
> and critical. Would it make sense to do adaptative min / max ? So when

hwmon has lcrit, min, max, and crit alarms for all sensor types, plus
an additional _cap_alarm for power attributes and _emergency_alarm
for temperature attributes. There is also a generic _alarm attribute
for each sensor, which is supposed to be used if the specific alarm
type is not known.

What exactly are the three levels of alarms ?

Thanks,
Guenter