Re: [PATCH 2/3] i8k: Autodetect maximal fan speed and fan RPM multiplier

From: Guenter Roeck
Date: Tue Dec 09 2014 - 15:21:19 EST

On Tue, Dec 09, 2014 at 09:07:00PM +0100, Pali Rohár wrote:
> This patch adds new function i8k_get_fan_nominal_rpm() 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 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 was 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@xxxxxxxxx>
> ---
> I tested this patch only on my Dell Latitude E6440 and autodetection worked fine
> Before appying this patch it should be tested on some other dell machines too
> but if machine does not support i8k_get_fan_nominal_rpm() driver should fallback
> to old values. So patch should be without regressions.

It looks like many of your error checks are unnecessary.
Why did you add those ?

Please refrain from adding unnecessary code.

Guenter

> ---
> drivers/char/i8k.c | 122 ++++++++++++++++++++++++++++++++++++++--------
> include/uapi/linux/i8k.h | 4 +-
> 2 files changed, 104 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
> index 31e4beb..8bdbed2 100644
> --- a/drivers/char/i8k.c
> +++ b/drivers/char/i8k.c
> @@ -42,12 +42,14 @@
> #define I8K_SMM_GET_FAN_SPEED 0x00a3
> #define I8K_SMM_SET_FAN_SPEED 0x01a3
> #define I8K_SMM_GET_FAN_RPM 0x02a3
> +#define I8K_SMM_GET_FAN_NOM_RPM 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 +66,9 @@ 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[I8K_FAN_COUNT];
> +static int i8k_pwm_mult[I8K_FAN_COUNT];
> +static int i8k_fan_max[I8K_FAN_COUNT];
>
> #define I8K_HWMON_HAVE_TEMP1 (1 << 0)
> #define I8K_HWMON_HAVE_TEMP2 (1 << 1)
> @@ -95,13 +97,13 @@ 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 rpm with");
> +MODULE_PARM_DESC(fan_mult, "Factor to multiply fan rpm 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 +273,25 @@ static int i8k_get_fan_rpm(int fan)
> {
> struct smm_regs regs = { .eax = I8K_SMM_GET_FAN_RPM, };
>
> + if (fan < 0 || fan >= I8K_FAN_COUNT)
> + 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_rpm(int fan, int speed)
> +{
> + struct smm_regs regs = { .eax = I8K_SMM_GET_FAN_NOM_RPM, };
> +
> + if (fan < 0 || fan >= I8K_FAN_COUNT)
> + return -EINVAL;
> +
> + regs.ebx = (fan & 0xff) | (speed << 8);
> + return i8k_smm(&regs) ? : (regs.eax & 0xffff) * i8k_fan_mult[fan];
> }
>
> /*
> @@ -282,9 +301,12 @@ static int i8k_set_fan_speed(int fan, int speed)
> {
> struct smm_regs regs = { .eax = I8K_SMM_SET_FAN_SPEED, };
>
> - 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 < I8K_FAN_COUNT && speed > i8k_fan_max[fan])
> + speed = i8k_fan_max[fan];
>
> + regs.ebx = (fan & 0xff) | (speed << 8);
> return i8k_smm(&regs) ? : i8k_get_fan_speed(fan);
> }
>
> @@ -559,10 +581,14 @@ static ssize_t i8k_hwmon_show_pwm(struct device *dev,
> int index = to_sensor_dev_attr(devattr)->index;
> int fan_speed;
>
> + if (index < 0 || index >= I8K_FAN_COUNT)
> + return -EINVAL;
> +
> fan_speed = i8k_get_fan_speed(index);
> if (fan_speed < 0)
> return -EIO;
> - return sprintf(buf, "%d\n", clamp_val(fan_speed * i8k_pwm_mult, 0, 255));
> + return sprintf(buf, "%d\n", clamp_val(fan_speed * i8k_pwm_mult[index],
> + 0, 255));
> }
>
> static ssize_t i8k_hwmon_set_pwm(struct device *dev,
> @@ -573,10 +599,14 @@ static ssize_t i8k_hwmon_set_pwm(struct device *dev,
> unsigned long val;
> int err;
>
> + if (index < 0 || index >= I8K_FAN_COUNT)
> + return -EINVAL;
> +
> 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_speed(index, val);
> @@ -854,7 +884,9 @@ 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 +915,66 @@ 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 == 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_mult <= 0) {
> + /*
> + * 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
> + */
> + for (fan = 0; fan < I8K_FAN_COUNT; ++fan) {
> + i8k_fan_mult[fan] = I8K_FAN_DEFAULT_MULT;
> + for (val = 0; val < 256; ++val) {
> + ret = i8k_get_fan_nominal_rpm(fan, val);
> + if (ret > I8K_FAN_MAX_RPM) {
> + i8k_fan_mult[fan] = 1;
> + break;
> + } else if (ret < 0) {
> + break;
> + }
> + }
> + }
> + } else {
> + /* Fan multiplier was specified in module param or in dmi */
> + for (fan = 0; fan < I8K_FAN_COUNT; ++fan)
> + i8k_fan_mult[fan] = fan_mult;
> }
> - i8k_pwm_mult = DIV_ROUND_UP(255, i8k_fan_max);
> +
> + if (fan_max <= 0) {
> + /*
> + * Autodetect maximal fan speed value for each fan
> + * Speed value is valid if i8k_get_fan_nominal_rpm() not fail
> + */
> + for (fan = 0; fan < I8K_FAN_COUNT; ++fan) {
> + for (val = 0; val < 256; ++val) {
> + if (i8k_get_fan_nominal_rpm(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;
> + }
> + } else {
> + /* Maximal fan speed was specified in module param or in dmi */
> + for (fan = 0; fan < I8K_FAN_COUNT; ++fan)
> + i8k_fan_max[fan] = fan_max;
> + }
> +
> + for (fan = 0; fan < I8K_FAN_COUNT; ++fan)
> + i8k_pwm_mult[fan] = DIV_ROUND_UP(255, i8k_fan_max[fan]);
>
> return 0;
> }
> diff --git a/include/uapi/linux/i8k.h b/include/uapi/linux/i8k.h
> index 133d02f..60ef0ea 100644
> --- a/include/uapi/linux/i8k.h
> +++ b/include/uapi/linux/i8k.h
> @@ -29,8 +29,10 @@
> #define I8K_GET_FAN _IOWR('i', 0x86, size_t)
> #define I8K_SET_FAN _IOWR('i', 0x87, size_t)
>
> -#define I8K_FAN_LEFT 1
> #define I8K_FAN_RIGHT 0
> +#define I8K_FAN_LEFT 1
> +#define I8K_FAN_COUNT (I8K_FAN_LEFT + 1)
> +
> #define I8K_FAN_OFF 0
> #define I8K_FAN_LOW 1
> #define I8K_FAN_HIGH 2
> --
> 1.7.9.5
>
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