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

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Date: Wed, 29 May 2024 07:07:17 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Amna Waseem <Amna.Waseem@...s.com>, 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 5/28/24 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.

> +		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