linux-kernel - Re: [PATCH 2/2] hwmon: (ina2xx) Add device tree support to pass alert polarity

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Date: Thu, 30 May 2024 10:06:46 +0200
From: Amna Waseem <Amna.Waseem@...s.com>
To: Guenter Roeck <linux@...ck-us.net>, Jean Delvare <jdelvare@...e.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, linux-hwmon@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, kernel@...s.com
Subject: Re: [PATCH 2/2] hwmon: (ina2xx) Add device tree support to pass alert
 polarity

On 5/29/24 16:07, Guenter Roeck wrote:
> On 5/28/24 23:07, Amna Waseem wrote:
>> The INA230 has an Alert pin which is asserted when the alert
>> function selected in the Mask/Enable register exceeds the
>> value programmed into the Alert Limit register. Assertion is based
>> on the Alert Polarity Bit (APOL, bit 1 of the Mask/Enable register).
>> It is default set to value 0 i.e Normal (active-low open collector).
>> However, hardware can be designed in such a way that expects Alert pin
>> to become active high if a user-defined threshold in Alert limit
>> register has been exceeded. This patch adds a way to pass alert polarity
>> value to the driver via device tree.
>>
>> Signed-off-by: Amna Waseem <Amna.Waseem@...s.com>
>> ---
>>   drivers/hwmon/ina2xx.c | 28 ++++++++++++++++++++++++++++
>>   1 file changed, 28 insertions(+)
>>
>> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
>> index d8415d1f21fc..b58e795bdc8f 100644
>> --- a/drivers/hwmon/ina2xx.c
>> +++ b/drivers/hwmon/ina2xx.c
>> @@ -73,6 +73,9 @@
>>   #define INA226_READ_AVG(reg)        (((reg) & INA226_AVG_RD_MASK) 
>> >> 9)
>>   #define INA226_SHIFT_AVG(val)        ((val) << 9)
>>   +#define INA226_ALERT_POLARITY_MASK        0x0002
>> +#define INA226_SHIFT_ALERT_POLARITY(val)    ((val) << 1)
>> +
>>   /* bit number of alert functions in Mask/Enable Register */
>>   #define INA226_SHUNT_OVER_VOLTAGE_BIT    15
>>   #define INA226_SHUNT_UNDER_VOLTAGE_BIT    14
>> @@ -178,6 +181,23 @@ static u16 ina226_interval_to_reg(int interval)
>>       return INA226_SHIFT_AVG(avg_bits);
>>   }
>>   +static int ina2xx_set_alert_polarity(struct ina2xx_data *data,
>> +                     unsigned long val)
>> +{
>> +    int ret;
>> +
>> +    if (val > INT_MAX || !(val == 0 || val == 1))
>
>     if (val != 0 && val !=1)
>
> would be sufficient and much easier to understand.


Agreed.

>
>> +        return -EINVAL;
>> +
>> +    mutex_lock(&data->config_lock);
>
> Pointless lock.
>
>> +    ret = regmap_update_bits(data->regmap, INA226_MASK_ENABLE,
>> +                 INA226_ALERT_POLARITY_MASK,
>> +                 INA226_SHIFT_ALERT_POLARITY(val));
>> +
>> +    mutex_unlock(&data->config_lock);
>> +    return ret;
>> +}
>> +
>>   /*
>>    * Calibration register is set to the best value, which eliminates
>>    * truncation errors on calculating current register in hardware.
>> @@ -659,6 +679,14 @@ static int ina2xx_probe(struct i2c_client *client)
>>       if (ret)
>>           return dev_err_probe(dev, ret, "failed to enable vs 
>> regulator\n");
>>   +    if (!of_property_read_u32(dev->of_node, "alert-polarity", 
>> &val)) {
>> +        ret = ina2xx_set_alert_polarity(data, val);
>> +        if (ret < 0)
>> +            return dev_err_probe(
>> +                dev, ret,
>> +                "failed to set APOL bit of Enable/Mask register\n");
>> +    }
>
> INA219 and INA220 do not support alert pin configuration (or, naturally,
> the mask register in the first place). This will need to be validated.
>
> Guenter
>
Would "of_property_read_bool" be sufficient to check whether the 
property exists or not for different chips? It means that if INA219 and 
INA220 are being used, they will not have a property "alert-polarity" 
defined in their devicetree so of_property_read_bool will return false 
and nothing will happen for these chips.