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Sender: Guenter Roeck <groeck7@gmail.com>
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Date: Wed, 22 May 2024 22:11:47 -0700
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Subject: Re: [PATCH 1/2] drivers: hwmon: max31827: Add PEC support
To: Radu Sabau <radu.sabau@analog.com>, Jean Delvare <jdelvare@suse.com>,
 Jonathan Corbet <corbet@lwn.net>, linux-hwmon@vger.kernel.org,
 linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20240522123923.22320-1-radu.sabau@analog.com>
 <20240522123923.22320-2-radu.sabau@analog.com>
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From: Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20240522123923.22320-2-radu.sabau@analog.com>
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On 5/22/24 05:39, Radu Sabau wrote:
> Add support for PEC by attaching PEC attribute to the i2c device.
> Add pec_store and pec_show function for accesing the "pec" file.
> 
accessing

> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> ---

There are lots of unrelated changes. Please drop all those, or
if they are supposed to fix checkpatch problems submit as separate
patches. I will not accept coding style changes unless they fix
checkpatch problems.

The patch is not based on the latest kernel. Please rebase
at least on top of v6.9.

More comments inline.

>   Documentation/hwmon/max31827.rst | 13 ++++-
>   drivers/hwmon/max31827.c         | 95 +++++++++++++++++++++++++++-----
>   2 files changed, 92 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
> index 44ab9dc064cb..9c11a9518c67 100644
> --- a/Documentation/hwmon/max31827.rst
> +++ b/Documentation/hwmon/max31827.rst
> @@ -131,7 +131,14 @@ The Fault Queue bits select how many consecutive temperature faults must occur
>   before overtemperature or undertemperature faults are indicated in the
>   corresponding status bits.
>   
> -Notes
> ------
> +PEC Support
> +-----------
> +
> +When reading a register value, the PEC byte is computed and sent by the chip.
> +
> +PEC on word data transaction respresents a signifcant increase in bandwitdh
> +usage (+33% for both write and reads) in normal conditions.
>   
> -PEC is not implemented.
> +Since this operation implies there will be an extra delay to each
> +transaction, PEC can be disabled or enabled through sysfs.
> +Just write 1  to the "pec" file for enabling PEC and 0 for disabling it.
> diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
> index f8a13b30f100..16a1524413db 100644
> --- a/drivers/hwmon/max31827.c
> +++ b/drivers/hwmon/max31827.c
> @@ -11,19 +11,20 @@
>   #include <linux/hwmon.h>
>   #include <linux/i2c.h>
>   #include <linux/mutex.h>
> -#include <linux/of_device.h>
>   #include <linux/regmap.h>
>   #include <linux/regulator/consumer.h>
> +#include <linux/of_device.h>
>   

Include files should be in alphabetic order. The above change
deserves a NACK.

> -#define MAX31827_T_REG			0x0
> +#define MAX31827_T_REG	0x0
>   #define MAX31827_CONFIGURATION_REG	0x2
> -#define MAX31827_TH_REG			0x4
> -#define MAX31827_TL_REG			0x6
> -#define MAX31827_TH_HYST_REG		0x8
> -#define MAX31827_TL_HYST_REG		0xA
> +#define MAX31827_TH_REG	0x4
> +#define MAX31827_TL_REG 0x6
> +#define MAX31827_TH_HYST_REG	0x8
> +#define MAX31827_TL_HYST_REG	0xA
>   
>   #define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
>   #define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
> +#define MAX31827_CONFIGURATION_PEC_EN_MASK	BIT(4)
>   #define MAX31827_CONFIGURATION_TIMEOUT_MASK	BIT(5)
>   #define MAX31827_CONFIGURATION_RESOLUTION_MASK	GENMASK(7, 6)
>   #define MAX31827_CONFIGURATION_ALRM_POL_MASK	BIT(8)
> @@ -46,6 +47,8 @@
>   #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
>   #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
>   
> +#define DEBUG_FS_DATA_MAX	16
> +
>   enum chips { max31827 = 1, max31828, max31829 };
>   
>   enum max31827_cnv {
> @@ -151,8 +154,8 @@ static int shutdown_write(struct max31827_state *st, unsigned int reg,
>   		goto unlock;
>   
>   	ret = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> -				 MAX31827_CONFIGURATION_CNV_RATE_MASK,
> -				 cnv_rate);
> +				   MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +				   cnv_rate);
>   
>   unlock:
>   	mutex_unlock(&st->lock);
> @@ -344,7 +347,7 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
>   		switch (attr) {
>   		case hwmon_temp_enable:
>   			if (val >> 1)
> -				return -EINVAL;
> +				return -EOPNOTSUPP;

Why ?

>   
>   			mutex_lock(&st->lock);
>   			/**
> @@ -384,7 +387,7 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
>   	case hwmon_chip:
>   		if (attr == hwmon_chip_update_interval) {
>   			if (!st->enable)
> -				return -EINVAL;
> +				return -EOPNOTSUPP;
>   
>   			/*
>   			 * Convert the desired conversion rate into register
> @@ -472,11 +475,60 @@ static ssize_t temp1_resolution_store(struct device *dev,
>   
>   	return ret ? ret : count;
>   }
> -
>   static DEVICE_ATTR_RW(temp1_resolution);
>   
> +static ssize_t pec_show(struct device *dev, struct device_attribute *devattr,
> +			char *buf)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", !!(client->flags & I2C_CLIENT_PEC));
> +}
> +
> +static ssize_t pec_store(struct device *dev, struct device_attribute *devattr,
> +			 const char *buf, size_t count)
> +{
> +	struct max31827_state *st = dev_get_drvdata(dev);
> +	struct i2c_client *client = to_i2c_client(dev);
> +	unsigned int val, val2;
> +	int err;
> +
> +	err = kstrtouint(buf, 10, &val);
> +	if (err < 0)
> +		return err;
> +
> +	val2 = FIELD_PREP(MAX31827_CONFIGURATION_PEC_EN_MASK, !!val);

This is completely unnecessary.

> +
> +	switch (val) {
> +	case 0:
> +		err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> +					 MAX31827_CONFIGURATION_PEC_EN_MASK,
> +					 val2);

	s/val2/0/

> +		if (err)
> +			return err;
> +
> +		client->flags &= ~I2C_CLIENT_PEC;
> +		break;
> +	case 1:
> +		err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> +					 MAX31827_CONFIGURATION_PEC_EN_MASK,
> +					 val2);

	s/val2/MAX31827_CONFIGURATION_PEC_EN_MASK/

> +		if (err)
> +			return err;
> +
> +		client->flags |= I2C_CLIENT_PEC;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(pec);
> +
>   static struct attribute *max31827_attrs[] = {
>   	&dev_attr_temp1_resolution.attr,
> +	&dev_attr_pec.attr,

Attach to i2c interface.

Oh, wait, you are doing that as well. So there would be two
"pec" attribute files, one attached to the i2c interface
and one attached to the hwmon interface. Care to explain ?

>   	NULL
>   };
>   ATTRIBUTE_GROUPS(max31827);
> @@ -493,8 +545,8 @@ static int max31827_init_client(struct max31827_state *st,
>   				struct device *dev)
>   {
>   	struct fwnode_handle *fwnode;
> +	unsigned int data, lsb_idx;
>   	unsigned int res = 0;
> -	u32 data, lsb_idx;

I am quite completely at loss trying to understand why you are making those changes.

>   	enum chips type;
>   	bool prop;
>   	int ret;
> @@ -578,6 +630,11 @@ static int max31827_init_client(struct max31827_state *st,
>   	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
>   }
>   
> +static void max31827_remove_pec(void *dev)
> +{
> +	device_remove_file(dev, &dev_attr_pec);
> +}
> +
>   static const struct hwmon_channel_info *max31827_info[] = {
>   	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
>   					 HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM |
> @@ -627,6 +684,16 @@ static int max31827_probe(struct i2c_client *client)
>   	if (err)
>   		return err;
>   
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_PEC)) {

This does not make sense. If the controller does not support PEC,
it does not make sense to provide an attribute to enable it.

> +		err = device_create_file(dev, &dev_attr_pec);
> +		if (err)
> +			return err;
> +
> +		err = devm_add_action_or_reset(dev, max31827_remove_pec, dev);
> +		if (err)
> +			return err;
> +	}
> +
>   	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
>   							 &max31827_chip_info,
>   							 max31827_groups);
> @@ -652,15 +719,17 @@ static const struct of_device_id max31827_of_match[] = {
>   MODULE_DEVICE_TABLE(of, max31827_of_match);
>   
>   static struct i2c_driver max31827_driver = {
> +	.class = I2C_CLASS_HWMON,
>   	.driver = {
>   		.name = "max31827",
>   		.of_match_table = max31827_of_match,
>   	},
> -	.probe = max31827_probe,
> +	.probe_new = max31827_probe,
>   	.id_table = max31827_i2c_ids,
>   };
>   module_i2c_driver(max31827_driver);
>   
>   MODULE_AUTHOR("Daniel Matyas <daniel.matyas@analog.com>");
> +MODULE_AUTHOR("Radu Sabau <radu.sabau@analog.com>");

Providing a patch to a driver does not make you the author.

>   MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
>   MODULE_LICENSE("GPL");