Date:	Sat, 20 Dec 2014 10:38:32 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Pali Rohár <pali.rohar@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	linux-kernel@...r.kernel.org, Valdis.Kletnieks@...edu,
	Steven Honeyman <stevenhoneyman@...il.com>,
	Jean Delvare <jdelvare@...e.de>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Jochen Eisinger <jochen@...guin-breeder.org>
Subject: Re: [PATCH v2 1/2] i8k: Autodetect maximal fan speed and fan RPM
 multiplier

On 12/19/2014 10:04 AM, Pali Rohár wrote:
> This patch adds new function i8k_get_fan_nominal_speed() for doing SMM call
> which will return nominal fan RPM for specified fan speed. It returns nominal
> RPM value at which fan operate when speed (0, 1, 2, 3) is set. It looks like
> RPM value is not accurate, but still provides very useful information.
>
> First it can be used to validate if certain fan speed could be accepted by SMM
> for setting fan speed and we can use this routine to detect maximal fan speed.
>
> Second it returns RPM value, so we can check if value looks correct with
> multiplier 30 or multiplier 1 (until now only these two multiplier were used).
> If RPM value with multiplier 30 is too high, then multiplier 1 is used.
>
> In case when SMM reports that new function is not supported we will fallback
> to old hardcoded values. Maximal fan speed would be 2 and RPM multiplier 30.
>
> Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> Tested-By: Pali Rohár <pali.rohar@...il.com>
> Tested-By: Steven Honeyman <stevenhoneyman@...il.com>
> Tested-By: Valdis Kletnieks <valdis.kletnieks@...edu>
> ---
>   drivers/char/i8k.c |  126 +++++++++++++++++++++++++++++++++++++++++++---------
>   1 file changed, 105 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
> index 48d701c..094a6b8 100644
> --- a/drivers/char/i8k.c
> +++ b/drivers/char/i8k.c
> @@ -6,6 +6,7 @@
>    * Hwmon integration:
>    * Copyright (C) 2011  Jean Delvare <jdelvare@...e.de>
>    * Copyright (C) 2013, 2014  Guenter Roeck <linux@...ck-us.net>
> + * Copyright (C) 2014  Pali Rohár <pali.rohar@...il.com>
>    *
>    * This program is free software; you can redistribute it and/or modify it
>    * under the terms of the GNU General Public License as published by the
> @@ -42,12 +43,14 @@
>   #define I8K_SMM_SET_FAN		0x01a3
>   #define I8K_SMM_GET_FAN		0x00a3
>   #define I8K_SMM_GET_SPEED	0x02a3
> +#define I8K_SMM_GET_NOM_SPEED	0x04a3
>   #define I8K_SMM_GET_TEMP	0x10a3
>   #define I8K_SMM_GET_TEMP_TYPE	0x11a3
>   #define I8K_SMM_GET_DELL_SIG1	0xfea3
>   #define I8K_SMM_GET_DELL_SIG2	0xffa3
>
> -#define I8K_FAN_MULT		30
> +#define I8K_FAN_DEFAULT_MULT	30
> +#define I8K_FAN_MAX_RPM		30000
>   #define I8K_MAX_TEMP		127
>
>   #define I8K_FN_NONE		0x00
> @@ -64,9 +67,9 @@ static DEFINE_MUTEX(i8k_mutex);
>   static char bios_version[4];
>   static struct device *i8k_hwmon_dev;
>   static u32 i8k_hwmon_flags;
> -static int i8k_fan_mult;
> -static int i8k_pwm_mult;
> -static int i8k_fan_max = I8K_FAN_HIGH;
> +static int i8k_fan_mult[2];
> +static int i8k_pwm_mult[2];
> +static int i8k_fan_max[2];
>
>   #define I8K_HWMON_HAVE_TEMP1	(1 << 0)
>   #define I8K_HWMON_HAVE_TEMP2	(1 << 1)
> @@ -95,13 +98,13 @@ static bool power_status;
>   module_param(power_status, bool, 0600);
>   MODULE_PARM_DESC(power_status, "Report power status in /proc/i8k");
>
> -static int fan_mult = I8K_FAN_MULT;
> +static int fan_mult;
>   module_param(fan_mult, int, 0);
> -MODULE_PARM_DESC(fan_mult, "Factor to multiply fan speed with");
> +MODULE_PARM_DESC(fan_mult, "Factor to multiply fan speed with (default: autodetect)");
>
> -static int fan_max = I8K_FAN_HIGH;
> +static int fan_max;
>   module_param(fan_max, int, 0);
> -MODULE_PARM_DESC(fan_max, "Maximum configurable fan speed");
> +MODULE_PARM_DESC(fan_max, "Maximum configurable fan speed (default: autodetect)");
>
>   static int i8k_open_fs(struct inode *inode, struct file *file);
>   static long i8k_ioctl(struct file *, unsigned int, unsigned long);
> @@ -271,8 +274,25 @@ static int i8k_get_fan_speed(int fan)
>   {
>   	struct smm_regs regs = { .eax = I8K_SMM_GET_SPEED, };
>
> +	if (fan < 0 || fan >= ARRAY_SIZE(i8k_fan_mult))
> +		return -EINVAL;
> +
>   	regs.ebx = fan & 0xff;
> -	return i8k_smm(&regs) ? : (regs.eax & 0xffff) * i8k_fan_mult;
> +	return i8k_smm(&regs) ? : (regs.eax & 0xffff) * i8k_fan_mult[fan];
> +}
> +
> +/*
> + * Read the fan nominal rpm for specific fan speed.
> + */
> +static int i8k_get_fan_nominal_speed(int fan, int speed)
> +{
> +	struct smm_regs regs = { .eax = I8K_SMM_GET_NOM_SPEED, };
> +
> +	if (fan < 0 || fan >= ARRAY_SIZE(i8k_fan_mult))
> +		return -EINVAL;
> +
> +	regs.ebx = (fan & 0xff) | (speed << 8);
> +	return i8k_smm(&regs) ? : (regs.eax & 0xffff) * i8k_fan_mult[fan];
>   }
>
>   /*
> @@ -282,9 +302,12 @@ static int i8k_set_fan(int fan, int speed)
>   {
>   	struct smm_regs regs = { .eax = I8K_SMM_SET_FAN, };
>
> -	speed = (speed < 0) ? 0 : ((speed > i8k_fan_max) ? i8k_fan_max : speed);
> -	regs.ebx = (fan & 0xff) | (speed << 8);
> +	if (speed < 0)
> +		speed = 0;
> +	if (fan >= 0 && fan < ARRAY_SIZE(i8k_fan_max) && speed > i8k_fan_max[fan])
> +		speed = i8k_fan_max[fan];
>
> +	regs.ebx = (fan & 0xff) | (speed << 8);
>   	return i8k_smm(&regs) ? : i8k_get_fan_status(fan);
>   }
>
> @@ -562,7 +585,8 @@ static ssize_t i8k_hwmon_show_pwm(struct device *dev,
>   	status = i8k_get_fan_status(index);
>   	if (status < 0)
>   		return -EIO;
> -	return sprintf(buf, "%d\n", clamp_val(status * i8k_pwm_mult, 0, 255));
> +	return sprintf(buf, "%d\n", clamp_val(status * i8k_pwm_mult[index],
> +					      0, 255));
>   }
>
>   static ssize_t i8k_hwmon_set_pwm(struct device *dev,
> @@ -576,7 +600,8 @@ static ssize_t i8k_hwmon_set_pwm(struct device *dev,
>   	err = kstrtoul(buf, 10, &val);
>   	if (err)
>   		return err;
> -	val = clamp_val(DIV_ROUND_CLOSEST(val, i8k_pwm_mult), 0, i8k_fan_max);
> +	val = clamp_val(DIV_ROUND_CLOSEST(val, i8k_pwm_mult[index]), 0,
> +			i8k_fan_max[index]);
>
>   	mutex_lock(&i8k_mutex);
>   	err = i8k_set_fan(index, val);
> @@ -854,7 +879,9 @@ MODULE_DEVICE_TABLE(dmi, i8k_dmi_table);
>    */
>   static int __init i8k_probe(void)
>   {
> +	const struct i8k_config_data *conf;
>   	const struct dmi_system_id *id;
> +	int fan, val, ret;
>
>   	/*
>   	 * Get DMI information
> @@ -883,18 +910,75 @@ static int __init i8k_probe(void)
>   			return -ENODEV;
>   	}
>
> -	i8k_fan_mult = fan_mult;
> -	i8k_fan_max = fan_max ? : I8K_FAN_HIGH;	/* Must not be 0 */
> +	/*
> +	 * Autodetect fan multiplier and maximal fan speed from dmi config
> +	 * Values specified in module parameters override values from dmi
> +	 */
>   	id = dmi_first_match(i8k_dmi_table);
>   	if (id && id->driver_data) {
> -		const struct i8k_config_data *conf = id->driver_data;
> +		conf = id->driver_data;
> +		if (fan_mult <= 0 && conf->fan_mult > 0)
> +			fan_mult = conf->fan_mult;
> +		if (fan_max <= 0 && conf->fan_max > 0)
> +			fan_max = conf->fan_max;
> +	}
> +
> +	if (fan_mult <= 0) {

Wonder what to do in the < 0 case. It might be better to make the variable
and the module parameter an unsigned int to cover that case, since a negative
multiplier doesn't really make sense. Same for fan_max.

> +		/*
> +		 * Autodetect fan multiplier for each fan based on nominal rpm
> +		 * First set default fan multiplier for each fan
> +		 * And if it reports rpm value too high then set multiplier to 1
> +		 *
> +		 * Try also setting multiplier from current rpm, but this will
> +		 * work only in case when fan is not turned off. It is better
> +		 * then nothing for machines which does not support nominal rpm
> +		 * SMM function.
> +		 */
> +		for (fan = 0; fan < ARRAY_SIZE(i8k_fan_mult); ++fan) {
> +			i8k_fan_mult[fan] = I8K_FAN_DEFAULT_MULT;
> +			if (i8k_get_fan_speed(fan) > I8K_FAN_MAX_RPM) {
> +				i8k_fan_mult[fan] = 1;
> +				continue;
> +			}

What if i8k_get_fan_speed(fan) returns an error ? Doesn't that imply that the fan
does not exist, and that you would not need the second loop in the first place ?

> +			for (val = 0; val < 256; ++val) {
> +				ret = i8k_get_fan_nominal_speed(fan, val);
> +				if (ret > I8K_FAN_MAX_RPM) {
> +					i8k_fan_mult[fan] = 1;
> +					break;
> +				} else if (ret < 0) {
> +					break;
> +				}

Traditionally error checks come first.

> +			}
> +		}
> +	} else {
> +		/* Fan multiplier was specified in module param or in dmi */
> +		for (fan = 0; fan < ARRAY_SIZE(i8k_fan_mult); ++fan)
> +			i8k_fan_mult[fan] = fan_mult;
> +	}
>
> -		if (fan_mult == I8K_FAN_MULT && conf->fan_mult)
> -			i8k_fan_mult = conf->fan_mult;
> -		if (fan_max == I8K_FAN_HIGH && conf->fan_max)
> -			i8k_fan_max = conf->fan_max;
> +	if (fan_max <= 0) {
> +		/*
> +		 * Autodetect maximal fan speed value for each fan
> +		 * Speed value is valid if i8k_get_fan_nominal_speed() not fail
> +		 */
> +		for (fan = 0; fan < ARRAY_SIZE(i8k_fan_max); ++fan) {
> +			for (val = 0; val < 256; ++val) {
> +				if (i8k_get_fan_nominal_speed(fan, val) < 0)
> +					break;
> +			}
> +			--val; /* set last value which not failed */
> +			if (val <= 0) /* Must not be 0 (and non negative) */
> +				val = I8K_FAN_HIGH;
> +			i8k_fan_max[fan] = val;

I kind of dislike that you are (at least potentially) looping through all
the nominal speeds twice; not sure how long that will delay the boot process.
I don't know if or how that can be solved easily, though. Either case,
I would prefer something like
			i8k_fan_max = I8K_FAN_HIGH;
			for (val = 0; val < 256; ++val) {
				if (i8k_get_fan_nominal_speed(fan, val) < 0)
					break;
				i8k_fan_max = val;
			}

since that would take care of all the meddling at the end.

> +		}
> +	} else {
> +		/* Maximal fan speed was specified in module param or in dmi */
> +		for (fan = 0; fan < ARRAY_SIZE(i8k_fan_max); ++fan)
> +			i8k_fan_max[fan] = fan_max;
>   	}

Overall I think it would make sense to move the auto-detection code to a separate
function. This is getting a bit large to have it all in a single function.

Thanks,
Guenter

> -	i8k_pwm_mult = DIV_ROUND_UP(255, i8k_fan_max);
> +
> +	for (fan = 0; fan < ARRAY_SIZE(i8k_pwm_mult); ++fan)
> +		i8k_pwm_mult[fan] = DIV_ROUND_UP(255, i8k_fan_max[fan]);
>
>   	return 0;
>   }
>

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