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Sender: Guenter Roeck <groeck7@gmail.com>
Subject: Re: [PATCH] hwmon: corsair-psu: add support for critical values
To:     Wilken Gottwalt <wilken.gottwalt@posteo.net>,
        linux-kernel@vger.kernel.org
Cc:     Jean Delvare <jdelvare@suse.com>, Jonathan Corbet <corbet@lwn.net>,
        linux-hwmon@vger.kernel.org
References: <YE4Ex4cslcSZsHHs@monster.powergraphx.local>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <4015dd7d-3cb1-193d-4aa3-fc0bc20f55a6@roeck-us.net>
Date:   Sun, 14 Mar 2021 11:22:01 -0700
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On 3/14/21 5:42 AM, Wilken Gottwalt wrote:
> Adds support for reading the critical values of the temperature sensors
> and the rail sensors (voltage and current) once and caches them. Updates
> the naming of the constants following a more clear scheme. Also updates
> the documentation and fixes a typo.
> 
> The new sensors output of a Corsair HX850i will look like this:
> corsairpsu-hid-3-1
> Adapter: HID adapter
> v_in:        230.00 V
> v_out +12v:   12.14 V  (crit min =  +8.41 V, crit max = +15.59 V)
> v_out +5v:     5.03 V  (crit min =  +3.50 V, crit max =  +6.50 V)
> v_out +3.3v:   3.30 V  (crit min =  +2.31 V, crit max =  +4.30 V)
> psu fan:        0 RPM
> vrm temp:     +46.2°C  (crit = +70.0°C)
> case temp:    +39.8°C  (crit = +70.0°C)
> power total: 152.00 W
> power +12v:  108.00 W
> power +5v:    41.00 W
> power +3.3v:   5.00 W
> curr in:          N/A
> curr +12v:     9.00 A  (crit max = +85.00 A)
> curr +5v:      8.31 A  (crit max = +40.00 A)
> curr +3.3v:    1.62 A  (crit max = +40.00 A)
> 
> This patch changes:
> - hwmon corsair-psu documentation
> - hwmon corsair-psu driver
> 
> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
> ---
>  Documentation/hwmon/corsair-psu.rst |  13 +-
>  drivers/hwmon/corsair-psu.c         | 185 ++++++++++++++++++++++------
>  2 files changed, 157 insertions(+), 41 deletions(-)
> 
> diff --git a/Documentation/hwmon/corsair-psu.rst b/Documentation/hwmon/corsair-psu.rst
> index 396b95c9a76a..b77e53810a13 100644
> --- a/Documentation/hwmon/corsair-psu.rst
> +++ b/Documentation/hwmon/corsair-psu.rst
> @@ -45,19 +45,30 @@ Sysfs entries
>  -------------
>  
>  =======================	========================================================
> +curr2_crit		Current max critical value on the 12v psu rail
> +curr3_crit		Current max critical value on the 5v psu rail
> +curr4_crit		Current max critical value on the 3.3v psu rail
>  curr1_input		Total current usage
>  curr2_input		Current on the 12v psu rail
>  curr3_input		Current on the 5v psu rail
>  curr4_input		Current on the 3.3v psu rail
>  fan1_input		RPM of psu fan
> +in1_crit		Voltage max critical value on the 12v psu rail
> +in2_crit		Voltage max critical value on the 5v psu rail
> +in3_crit		Voltage max critical value on the 3.3v psu rail
>  in0_input		Voltage of the psu ac input
>  in1_input		Voltage of the 12v psu rail
>  in2_input		Voltage of the 5v psu rail
> -in3_input		Voltage of the 3.3 psu rail
> +in3_input		Voltage of the 3.3v psu rail
> +in1_lcrit		Voltage min critical value on the 12v psu rail
> +in2_lcrit		Voltage min critical value on the 5v psu rail
> +in3_lcrit		Voltage min critical value on the 3.3v psu rail
>  power1_input		Total power usage
>  power2_input		Power usage of the 12v psu rail
>  power3_input		Power usage of the 5v psu rail
>  power4_input		Power usage of the 3.3v psu rail
> +temp1_crit		Temperature max cirtical value of the psu vrm component
> +temp2_crit		Temperature max critical value of psu case
>  temp1_input		Temperature of the psu vrm component
>  temp2_input		Temperature of the psu case
>  =======================	========================================================
> diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
> index b0953eeeb2d3..141a5079ea7e 100644
> --- a/drivers/hwmon/corsair-psu.c
> +++ b/drivers/hwmon/corsair-psu.c
> @@ -53,11 +53,21 @@
>  #define CMD_TIMEOUT_MS		250
>  #define SECONDS_PER_HOUR	(60 * 60)
>  #define SECONDS_PER_DAY		(SECONDS_PER_HOUR * 24)
> +#define RAIL_COUNT		3 /* 3v3 + 5v + 12v */
> +#define CRIT_VALUES_COUNT	11 /* 2 temp crit + 6 rail volts (low and high) + 3 rails amps */
> +#define TEMP_HCRIT		0
> +#define VOLTS_RAIL_HCRIT	2
> +#define VOLTS_RAIL_LCRIT	5
> +#define AMPS_RAIL_HCRIT		8
>  
>  #define PSU_CMD_SELECT_RAIL	0x00 /* expects length 2 */
> -#define PSU_CMD_IN_VOLTS	0x88 /* the rest of the commands expect length 3 */
> +#define PSU_CMD_RAIL_VOLTS_HCRIT 0x40 /* the rest of the commands expect length 3 */
> +#define PSU_CMD_RAIL_VOLTS_LCRIT 0x44
> +#define PSU_CMD_RAIL_AMPS_HCRIT	0x46
> +#define PSU_CMD_TEMP_HCRIT	0x4F
> +#define PSU_CMD_IN_VOLTS	0x88
>  #define PSU_CMD_IN_AMPS		0x89
> -#define PSU_CMD_RAIL_OUT_VOLTS	0x8B
> +#define PSU_CMD_RAIL_VOLTS	0x8B
>  #define PSU_CMD_RAIL_AMPS	0x8C
>  #define PSU_CMD_TEMP0		0x8D
>  #define PSU_CMD_TEMP1		0x8E
> @@ -113,6 +123,7 @@ struct corsairpsu_data {
>  	struct dentry *debugfs;
>  	struct completion wait_completion;
>  	struct mutex lock; /* for locking access to cmd_buffer */
> +	long crit_values[CRIT_VALUES_COUNT];
>  	u8 *cmd_buffer;
>  	char vendor[REPLY_SIZE];
>  	char product[REPLY_SIZE];
> @@ -193,7 +204,10 @@ static int corsairpsu_request(struct corsairpsu_data *priv, u8 cmd, u8 rail, voi
>  
>  	mutex_lock(&priv->lock);
>  	switch (cmd) {
> -	case PSU_CMD_RAIL_OUT_VOLTS:
> +	case PSU_CMD_RAIL_VOLTS_HCRIT:
> +	case PSU_CMD_RAIL_VOLTS_LCRIT:
> +	case PSU_CMD_RAIL_AMPS_HCRIT:
> +	case PSU_CMD_RAIL_VOLTS:
>  	case PSU_CMD_RAIL_AMPS:
>  	case PSU_CMD_RAIL_WATTS:
>  		ret = corsairpsu_usb_cmd(priv, 2, PSU_CMD_SELECT_RAIL, rail, NULL);
> @@ -229,9 +243,13 @@ static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, l
>  	 */
>  	tmp = ((long)data[3] << 24) + (data[2] << 16) + (data[1] << 8) + data[0];
>  	switch (cmd) {
> +	case PSU_CMD_RAIL_VOLTS_HCRIT:
> +	case PSU_CMD_RAIL_VOLTS_LCRIT:
> +	case PSU_CMD_RAIL_AMPS_HCRIT:
> +	case PSU_CMD_TEMP_HCRIT:
>  	case PSU_CMD_IN_VOLTS:
>  	case PSU_CMD_IN_AMPS:
> -	case PSU_CMD_RAIL_OUT_VOLTS:
> +	case PSU_CMD_RAIL_VOLTS:
>  	case PSU_CMD_RAIL_AMPS:
>  	case PSU_CMD_TEMP0:
>  	case PSU_CMD_TEMP1:
> @@ -256,18 +274,70 @@ static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, l
>  	return ret;
>  }
>  
> +static void corsairpsu_get_criticals(struct corsairpsu_data *priv)
> +{
> +	long tmp;
> +	int rail;
> +	int ret;
> +
> +	ret = corsairpsu_get_value(priv, PSU_CMD_TEMP_HCRIT, 0, &tmp);
> +	if (ret < 0)
> +		pr_debug("%s: unable to read temp0 critical value\n", DRIVER_NAME);
> +	else
> +		priv->crit_values[TEMP_HCRIT] = tmp;
> +
> +	ret = corsairpsu_get_value(priv, PSU_CMD_TEMP_HCRIT, 1, &tmp);
> +	if (ret < 0)
> +		pr_debug("%s: unable to read temp1 cirtical value\n", DRIVER_NAME);
> +	else
> +		priv->crit_values[TEMP_HCRIT + 1] = tmp;
> +
> +	for (rail = 0; rail < RAIL_COUNT; ++rail) {
> +		ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_VOLTS_HCRIT, rail, &tmp);
> +		if (ret < 0) {
> +			pr_debug("%s: unable to read volts rail %d high critical value\n",
> +				 DRIVER_NAME, rail);
> +		} else {
> +			priv->crit_values[VOLTS_RAIL_HCRIT + rail] = tmp;
> +		}
> +	}
> +
> +	for (rail = 0; rail < RAIL_COUNT; ++rail) {
> +		ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_VOLTS_LCRIT, rail, &tmp);
> +		if (ret < 0) {
> +			pr_debug("%s: unable to read volts rail %d low critical value\n",
> +				 DRIVER_NAME, rail);
> +		} else {
> +			priv->crit_values[VOLTS_RAIL_LCRIT + rail] = tmp;
> +		}

I am not happy with this code. First, it is quite complex. Second,
it uses crit_values[] to indicate both valid limits and error codes.
That is mostly fine until there is ever a negative limit (which can happen
if there is ever a low temperature limit).

It would be much better to have a limit_supported bit map as well as limit arrays.
On top of that, I am not sure if bundling all limits into a single array is worth it.
Something like

		ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_VOLTS_LCRIT, rail, &tmp);
		if (ret == 0) {
			priv->lcrit_in_supported |= BIT(rail);
			priv->lcrit_in[rail] = tmp;
		}

would be much easier to understand, and it would and be much less error prone.

The is_visible function could then simply check for
		if (priv->lcrit_in_supported & BIT(channel))
to determine if limits are supported for a channel.

I also don't see a value in the debug messages. That is either is a bug, or it is
normal operation for some PSUs. If it is a bug, it should be reported as such
and result in an error. If it is normal operation, the result can be seen
in the non-existing attribute, and there is no need for an extra message.

> +	}
> +
> +	for (rail = 0; rail < RAIL_COUNT; ++rail) {
> +		ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_AMPS_HCRIT, rail, &tmp);
> +		if (ret < 0) {
> +			pr_debug("%s: unable to read amps rail %d hight critical value\n",
> +				 DRIVER_NAME, rail);
> +		} else {
> +			priv->crit_values[AMPS_RAIL_HCRIT + rail] = tmp;
> +		}
> +	}
> +}
> +
>  static umode_t corsairpsu_hwmon_ops_is_visible(const void *data, enum hwmon_sensor_types type,
>  					       u32 attr, int channel)
>  {
> -	if (type == hwmon_temp && (attr == hwmon_temp_input || attr == hwmon_temp_label))
> +	if (type == hwmon_temp && (attr == hwmon_temp_input || attr == hwmon_temp_label ||
> +				   attr == hwmon_temp_crit))
>  		return 0444;
>  	else if (type == hwmon_fan && (attr == hwmon_fan_input || attr == hwmon_fan_label))
>  		return 0444;
>  	else if (type == hwmon_power && (attr == hwmon_power_input || attr == hwmon_power_label))
>  		return 0444;
> -	else if (type == hwmon_in && (attr == hwmon_in_input || attr == hwmon_in_label))
> +	else if (type == hwmon_in && (attr == hwmon_in_input || attr == hwmon_in_label ||
> +				      attr == hwmon_in_lcrit || attr == hwmon_in_crit))
>  		return 0444;
> -	else if (type == hwmon_curr && (attr == hwmon_curr_input || attr == hwmon_curr_label))
> +	else if (type == hwmon_curr && (attr == hwmon_curr_input || attr == hwmon_curr_label ||
> +					attr == hwmon_curr_crit))
>  		return 0444;
>  
>  	return 0;
> @@ -277,11 +347,18 @@ static int corsairpsu_hwmon_ops_read(struct device *dev, enum hwmon_sensor_types
>  				     int channel, long *val)
>  {
>  	struct corsairpsu_data *priv = dev_get_drvdata(dev);
> -	int ret;
> -
> -	if (type == hwmon_temp && attr == hwmon_temp_input && channel < 2) {
> -		ret = corsairpsu_get_value(priv, channel ? PSU_CMD_TEMP1 : PSU_CMD_TEMP0, channel,
> -					   val);
> +	int ret = 0;
> +
> +	if (type == hwmon_temp && channel < 2) {
> +		if (attr == hwmon_temp_input) {
> +			ret = corsairpsu_get_value(priv, channel ? PSU_CMD_TEMP1 : PSU_CMD_TEMP0,
> +						   channel, val);
> +		} else if (attr == hwmon_temp_crit) {
> +			if (priv->crit_values[TEMP_HCRIT + channel] != -EOPNOTSUPP)
> +				*val = priv->crit_values[TEMP_HCRIT + channel];
> +			else
> +				ret = -EOPNOTSUPP;
> +		}
>  	} else if (type == hwmon_fan && attr == hwmon_fan_input) {
>  		ret = corsairpsu_get_value(priv, PSU_CMD_FAN, 0, val);
>  	} else if (type == hwmon_power && attr == hwmon_power_input) {
> @@ -295,27 +372,48 @@ static int corsairpsu_hwmon_ops_read(struct device *dev, enum hwmon_sensor_types
>  		default:
>  			return -EOPNOTSUPP;
>  		}
> -	} else if (type == hwmon_in && attr == hwmon_in_input) {
> -		switch (channel) {
> -		case 0:
> -			ret = corsairpsu_get_value(priv, PSU_CMD_IN_VOLTS, 0, val);
> -			break;
> -		case 1 ... 3:
> -			ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_OUT_VOLTS, channel - 1, val);
> -			break;
> -		default:
> -			return -EOPNOTSUPP;
> +	} else if (type == hwmon_in) {
> +		if (attr == hwmon_in_input) {
> +			switch (channel) {
> +			case 0:
> +				ret = corsairpsu_get_value(priv, PSU_CMD_IN_VOLTS, 0, val);
> +				break;
> +			case 1 ... 3:
> +				ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_VOLTS, channel - 1,
> +							   val);
> +				break;
> +			default:
> +				return -EOPNOTSUPP;
> +			}
> +		} else if (attr == hwmon_in_crit && channel > 0 && channel < 4) {
> +			if (priv->crit_values[VOLTS_RAIL_HCRIT + channel - 1] != -EOPNOTSUPP)
> +				*val = priv->crit_values[VOLTS_RAIL_HCRIT + channel - 1];
> +			else
> +				ret = -EOPNOTSUPP;
> +		} else if (attr == hwmon_in_lcrit && channel > 0 && channel < 4) {
> +			if (priv->crit_values[VOLTS_RAIL_LCRIT + channel - 1] != -EOPNOTSUPP)
> +				*val = priv->crit_values[VOLTS_RAIL_LCRIT + channel - 1];
> +			else
> +				ret = -EOPNOTSUPP;
>  		}
> -	} else if (type == hwmon_curr && attr == hwmon_curr_input) {
> -		switch (channel) {
> -		case 0:
> -			ret = corsairpsu_get_value(priv, PSU_CMD_IN_AMPS, 0, val);
> -			break;
> -		case 1 ... 3:
> -			ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_AMPS, channel - 1, val);
> -			break;
> -		default:
> -			return -EOPNOTSUPP;
> +	} else if (type == hwmon_curr) {
> +		if (attr == hwmon_curr_input) {
> +			switch (channel) {
> +			case 0:
> +				ret = corsairpsu_get_value(priv, PSU_CMD_IN_AMPS, 0, val);
> +				break;
> +			case 1 ... 3:
> +				ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_AMPS, channel - 1,
> +							   val);
> +				break;
> +			default:
> +				return -EOPNOTSUPP;
> +			}
> +		} else if (attr == hwmon_curr_crit && channel > 0 && channel < 4) {
> +			if (priv->crit_values[AMPS_RAIL_HCRIT + channel - 1] != -EOPNOTSUPP)
> +				*val = priv->crit_values[AMPS_RAIL_HCRIT + channel - 1];
> +			else
> +				ret = -EOPNOTSUPP;
>  		}

Due to the channel range check, this returns a random value if the function is ever called
with attr == hwmon_curr_crit && channel == 0. This shows that the channel check is
really unnecessary (but also that the code is getting dificult to understand).

>  	} else {
>  		return -EOPNOTSUPP;

I think it is time to split this code into per-type functions. It is getting unreadable.

> @@ -360,8 +458,8 @@ static const struct hwmon_channel_info *corsairpsu_info[] = {
>  	HWMON_CHANNEL_INFO(chip,
>  			   HWMON_C_REGISTER_TZ),
>  	HWMON_CHANNEL_INFO(temp,
> -			   HWMON_T_INPUT | HWMON_T_LABEL,
> -			   HWMON_T_INPUT | HWMON_T_LABEL),
> +			   HWMON_T_INPUT | HWMON_T_LABEL | HWMON_T_CRIT,
> +			   HWMON_T_INPUT | HWMON_T_LABEL | HWMON_T_CRIT),
>  	HWMON_CHANNEL_INFO(fan,
>  			   HWMON_F_INPUT | HWMON_F_LABEL),
>  	HWMON_CHANNEL_INFO(power,
> @@ -371,14 +469,14 @@ static const struct hwmon_channel_info *corsairpsu_info[] = {
>  			   HWMON_P_INPUT | HWMON_P_LABEL),
>  	HWMON_CHANNEL_INFO(in,
>  			   HWMON_I_INPUT | HWMON_I_LABEL,
> -			   HWMON_I_INPUT | HWMON_I_LABEL,
> -			   HWMON_I_INPUT | HWMON_I_LABEL,
> -			   HWMON_I_INPUT | HWMON_I_LABEL),
> +			   HWMON_I_INPUT | HWMON_I_LABEL | HWMON_I_LCRIT | HWMON_I_CRIT,
> +			   HWMON_I_INPUT | HWMON_I_LABEL | HWMON_I_LCRIT | HWMON_I_CRIT,
> +			   HWMON_I_INPUT | HWMON_I_LABEL | HWMON_I_LCRIT | HWMON_I_CRIT),
>  	HWMON_CHANNEL_INFO(curr,
>  			   HWMON_C_INPUT | HWMON_C_LABEL,
> -			   HWMON_C_INPUT | HWMON_C_LABEL,
> -			   HWMON_C_INPUT | HWMON_C_LABEL,
> -			   HWMON_C_INPUT | HWMON_C_LABEL),
> +			   HWMON_C_INPUT | HWMON_C_LABEL | HWMON_C_CRIT,
> +			   HWMON_C_INPUT | HWMON_C_LABEL | HWMON_C_CRIT,
> +			   HWMON_C_INPUT | HWMON_C_LABEL | HWMON_C_CRIT),
>  	NULL
>  };
>  
> @@ -472,6 +570,7 @@ static void corsairpsu_debugfs_init(struct corsairpsu_data *priv)
>  static int corsairpsu_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  {
>  	struct corsairpsu_data *priv;
> +	int i;
>  	int ret;
>  
>  	priv = devm_kzalloc(&hdev->dev, sizeof(struct corsairpsu_data), GFP_KERNEL);
> @@ -482,6 +581,9 @@ static int corsairpsu_probe(struct hid_device *hdev, const struct hid_device_id
>  	if (!priv->cmd_buffer)
>  		return -ENOMEM;
>  
> +	for (i = 0; i < CRIT_VALUES_COUNT; ++i)
> +		priv->crit_values[i] = -EOPNOTSUPP;
> +
>  	ret = hid_parse(hdev);
>  	if (ret)
>  		return ret;
> @@ -513,6 +615,9 @@ static int corsairpsu_probe(struct hid_device *hdev, const struct hid_device_id
>  		goto fail_and_stop;
>  	}
>  
> +	/* this can fail and is considered non-fatal */
> +	corsairpsu_get_criticals(priv);
> +

The comment does not add value, but it does add confusion. "Fail" implies
that something is wrong. However, I suspect that it only means that not all
power supplies report limits. That is not a failure, it is normal operation.

Thanks,
Guenter

>  	priv->hwmon_dev = hwmon_device_register_with_info(&hdev->dev, "corsairpsu", priv,
>  							  &corsairpsu_chip_info, 0);
>  
>