This patch exports standard hwmon pwmX_enable sysfs attribute for
enabling or disabling automatic fan control by BIOS. Standard value
"1" is for disabling automatic BIOS fan control and value "2" for
enabling.
By default BIOS auto mode is enabled by laptop firmware.
When BIOS auto mode is enabled, custom fan speed value (set via hwmon
pwmX sysfs attribute) is overwritten by SMM in few seconds and
therefore any custom settings are without effect. So this is reason
why implementing option for disabling BIOS auto mode is needed.
So finally this patch allows kernel to set and control fan speed on
laptops, but it can be dangerous (like setting speed of other fans).
The SMM commands to enable or disable automatic fan control are not
documented and are not the same on all Dell laptops. Therefore a
whitelist is used to send the correct codes only on laptopts for which
they are known.
This patch was originally developed by Pali Rohár; later Giovanni
Mascellani implemented the whitelist.
Signed-off-by: Giovanni Mascellani <[email protected]>
Co-Developed-by: Pali Rohár <[email protected]>
Signed-off-by: Pali Rohár <[email protected]>
---
drivers/hwmon/dell-smm-hwmon.c | 114 ++++++++++++++++++++++++++++++---
1 file changed, 104 insertions(+), 10 deletions(-)
diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 4212d022d253..25d160b36a57 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -68,6 +68,8 @@ static uint i8k_pwm_mult;
static uint i8k_fan_max = I8K_FAN_HIGH;
static bool disallow_fan_type_call;
static bool disallow_fan_support;
+static unsigned int manual_fan;
+static unsigned int auto_fan;
#define I8K_HWMON_HAVE_TEMP1 (1 << 0)
#define I8K_HWMON_HAVE_TEMP2 (1 << 1)
@@ -300,6 +302,20 @@ static int i8k_get_fan_nominal_speed(int fan, int speed)
return i8k_smm(®s) ? : (regs.eax & 0xffff) * i8k_fan_mult;
}
+/*
+ * Enable or disable automatic BIOS fan control support
+ */
+static int i8k_enable_fan_auto_mode(bool enable)
+{
+ struct smm_regs regs = { };
+
+ if (disallow_fan_support)
+ return -EINVAL;
+
+ regs.eax = enable ? auto_fan : manual_fan;
+ return i8k_smm(®s);
+}
+
/*
* Set the fan speed (off, low, high). Returns the new fan status.
*/
@@ -726,6 +742,35 @@ static ssize_t i8k_hwmon_pwm_store(struct device *dev,
return err < 0 ? -EIO : count;
}
+static ssize_t i8k_hwmon_pwm_enable_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ bool enable;
+ unsigned long val;
+
+ if (!auto_fan)
+ return -ENODEV;
+
+ err = kstrtoul(buf, 10, &val);
+ if (err)
+ return err;
+
+ if (val == 1)
+ enable = false;
+ else if (val == 2)
+ enable = true;
+ else
+ return -EINVAL;
+
+ mutex_lock(&i8k_mutex);
+ err = i8k_enable_fan_auto_mode(enable);
+ mutex_unlock(&i8k_mutex);
+
+ return err ? err : count;
+}
+
static SENSOR_DEVICE_ATTR_RO(temp1_input, i8k_hwmon_temp, 0);
static SENSOR_DEVICE_ATTR_RO(temp1_label, i8k_hwmon_temp_label, 0);
static SENSOR_DEVICE_ATTR_RO(temp2_input, i8k_hwmon_temp, 1);
@@ -749,6 +794,7 @@ static SENSOR_DEVICE_ATTR_RO(temp10_label, i8k_hwmon_temp_label, 9);
static SENSOR_DEVICE_ATTR_RO(fan1_input, i8k_hwmon_fan, 0);
static SENSOR_DEVICE_ATTR_RO(fan1_label, i8k_hwmon_fan_label, 0);
static SENSOR_DEVICE_ATTR_RW(pwm1, i8k_hwmon_pwm, 0);
+static SENSOR_DEVICE_ATTR_WO(pwm1_enable, i8k_hwmon_pwm_enable, 0);
static SENSOR_DEVICE_ATTR_RO(fan2_input, i8k_hwmon_fan, 1);
static SENSOR_DEVICE_ATTR_RO(fan2_label, i8k_hwmon_fan_label, 1);
static SENSOR_DEVICE_ATTR_RW(pwm2, i8k_hwmon_pwm, 1);
@@ -780,12 +826,13 @@ static struct attribute *i8k_attrs[] = {
&sensor_dev_attr_fan1_input.dev_attr.attr, /* 20 */
&sensor_dev_attr_fan1_label.dev_attr.attr, /* 21 */
&sensor_dev_attr_pwm1.dev_attr.attr, /* 22 */
- &sensor_dev_attr_fan2_input.dev_attr.attr, /* 23 */
- &sensor_dev_attr_fan2_label.dev_attr.attr, /* 24 */
- &sensor_dev_attr_pwm2.dev_attr.attr, /* 25 */
- &sensor_dev_attr_fan3_input.dev_attr.attr, /* 26 */
- &sensor_dev_attr_fan3_label.dev_attr.attr, /* 27 */
- &sensor_dev_attr_pwm3.dev_attr.attr, /* 28 */
+ &sensor_dev_attr_pwm1_enable.dev_attr.attr, /* 23 */
+ &sensor_dev_attr_fan2_input.dev_attr.attr, /* 24 */
+ &sensor_dev_attr_fan2_label.dev_attr.attr, /* 25 */
+ &sensor_dev_attr_pwm2.dev_attr.attr, /* 26 */
+ &sensor_dev_attr_fan3_input.dev_attr.attr, /* 27 */
+ &sensor_dev_attr_fan3_label.dev_attr.attr, /* 28 */
+ &sensor_dev_attr_pwm3.dev_attr.attr, /* 29 */
NULL
};
@@ -828,16 +875,19 @@ static umode_t i8k_is_visible(struct kobject *kobj, struct attribute *attr,
!(i8k_hwmon_flags & I8K_HWMON_HAVE_TEMP10))
return 0;
- if (index >= 20 && index <= 22 &&
+ if (index >= 20 && index <= 23 &&
!(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN1))
return 0;
- if (index >= 23 && index <= 25 &&
+ if (index >= 24 && index <= 26 &&
!(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN2))
return 0;
- if (index >= 26 && index <= 28 &&
+ if (index >= 27 && index <= 29 &&
!(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN3))
return 0;
+ if (index == 23 && !auto_fan)
+ return 0;
+
return attr->mode;
}
@@ -1135,12 +1185,48 @@ static struct dmi_system_id i8k_blacklist_fan_support_dmi_table[] __initdata = {
{ }
};
+struct i8k_fan_control_data {
+ unsigned int manual_fan;
+ unsigned int auto_fan;
+};
+
+enum i8k_fan_controls {
+ I8K_FAN_34A3_35A3,
+};
+
+static const struct i8k_fan_control_data i8k_fan_control_data[] = {
+ [I8K_FAN_34A3_35A3] = {
+ .manual_fan = 0x34a3,
+ .auto_fan = 0x35a3,
+ },
+};
+
+static struct dmi_system_id i8k_whitelist_fan_control[] __initdata = {
+ {
+ .ident = "Dell Precision 5530",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Precision 5530"),
+ },
+ .driver_data = (void *)&i8k_fan_control_data[I8K_FAN_34A3_35A3],
+ },
+ {
+ .ident = "Dell Latitude E6440",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Latitude E6440"),
+ },
+ .driver_data = (void *)&i8k_fan_control_data[I8K_FAN_34A3_35A3],
+ },
+ { }
+};
+
/*
* Probe for the presence of a supported laptop.
*/
static int __init i8k_probe(void)
{
- const struct dmi_system_id *id;
+ const struct dmi_system_id *id, *fan_control;
int fan, ret;
/*
@@ -1200,6 +1286,14 @@ static int __init i8k_probe(void)
i8k_fan_max = fan_max ? : I8K_FAN_HIGH; /* Must not be 0 */
i8k_pwm_mult = DIV_ROUND_UP(255, i8k_fan_max);
+ fan_control = dmi_first_match(i8k_whitelist_fan_control);
+ if (fan_control && fan_control->driver_data) {
+ const struct i8k_fan_control_data *fan_control_data = fan_control->driver_data;
+ manual_fan = fan_control_data->manual_fan;
+ auto_fan = fan_control_data->auto_fan;
+ pr_info("enabling support for setting automatic/manual fan control\n");
+ }
+
if (!fan_mult) {
/*
* Autodetect fan multiplier based on nominal rpm
--
2.24.0
Part of the documentation is taken from the README of the userspace
utils (https://github.com/vitorafsr/i8kutils). The license is GPL-2+
and the author Massimo Dal Zotto is already credited as author of
the module. Therefore there should be no copyright problem.
I also added a paragraph with specific information on the experimental
support for automatic BIOS fan control.
Signed-off-by: Giovanni Mascellani <[email protected]>
---
Documentation/hwmon/dell-smm-hwmon.rst | 157 +++++++++++++++++++++++++
Documentation/hwmon/index.rst | 1 +
2 files changed, 158 insertions(+)
create mode 100644 Documentation/hwmon/dell-smm-hwmon.rst
diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst
new file mode 100644
index 000000000000..25bd8f8e89b5
--- /dev/null
+++ b/Documentation/hwmon/dell-smm-hwmon.rst
@@ -0,0 +1,157 @@
+Kernel driver dell-smm-hwmon
+============================
+
+Description
+-----------
+
+On many Dell laptops the System Management Mode (SMM) BIOS can be
+queried for the status of fans and temperature sensors. Userspace
+utilities like ``sensors`` can be used to return the readings. The
+userspace suite `i8kutils`__ can also be used to read the sensors and
+automatically adjust fan speed (please notice that it currently uses
+the deprecated ``/proc/i8k`` interface).
+
+ __ https://github.com/vitorafsr/i8kutils
+
+``sysfs`` interface
+-------------------
+
+Temperature sensors and fans can be queried and set via the standard
+``hwmon`` interface on ``sysfs``, under the directory
+``/sys/class/hwmon/hwmonX`` for some value of ``X`` (search for the
+``X`` such that ``/sys/class/hwmon/hwmonX/name`` has content
+``dell_smm``). A number of other attributes can be read or written:
+
+=============================== ======= =======================================
+Name Perm Description
+=============================== ======= =======================================
+fan[1-3]_input RO Fan speed in RPM.
+fan[1-3]_label RO Fan label.
+pwm[1-3] RW Control the fan PWM duty-cycle.
+pwm1_enable WO Enable or disable automatic BIOS fan
+ control (not supported on all laptops,
+ see below for details).
+temp[1-10]_input RO Temperature reading in milli-degrees
+ Celsius.
+temp[1-10]_label RO Temperature sensor label.
+=============================== ======= =======================================
+
+Disabling automatic BIOS fan control
+------------------------------------
+
+On some laptops the BIOS automatically sets fan speed every few
+seconds. Therefore the fan speed set by mean of this driver is quickly
+overwritten.
+
+There is experimental support for disabling automatic BIOS fan
+control, at least on laptops where the corresponding SMM command is
+known, by writing the value ``1`` in the attribute ``pwm1_enable``
+(writing ``2`` enables automatic BIOS control again). Even if you have
+more than one fan, all of them are set to either enabled or disabled
+automatic fan control at the same time and, notwithstanding the name,
+``pwm1_enable`` sets automatic control for all fans.
+
+If ``pwm1_enable`` is not available, then it means that SMM codes for
+enabling and disabling automatic BIOS fan control are not whitelisted
+for your hardware. It is possible that codes that work for other
+laptops actually work for yours as well, or that you have to discover
+new codes.
+
+Check the list ``i8k_whitelist_fan_control`` in file
+``drivers/hwmon/dell-smm-hwmon.c`` in the kernel tree: as a first
+attempt you can try to add your machine and use an already-known code
+pair. If, after recompiling the kernel, you see that ``pwm1_enable``
+is present and works (i.e., you can manually control the fan speed),
+then please submit your finding as a kernel patch, so that other users
+can benefit from it. Please see
+:ref:`Documentation/process/submitting-patches <submittingpatches>`
+for information on submitting patches.
+
+If no known code works on your machine, you need to resort to do some
+probing, because unfortunately Dell does not publish datasheets for
+its SMM. You can experiment with the code in `this repository`__ to
+probe the BIOS on your machine and discover the appropriate codes.
+
+ __ https://github.com/clopez/dellfan/
+
+Again, when you find new codes, we'd be happy to have your patches!
+
+Module parameters
+-----------------
+
+* force:bool
+ Force loading without checking for supported
+ models. (default: 0)
+
+* ignore_dmi:bool
+ Continue probing hardware even if DMI data does not
+ match. (default: 0)
+
+* restricted:bool
+ Allow fan control only to processes with the
+ ``CAP_SYS_ADMIN`` capability set or processes run
+ as root when using the legacy ``/proc/i8k``
+ interface. In this case normal users will be able
+ to read temperature and fan status but not to
+ control the fan. If your notebook is shared with
+ other users and you don't trust them you may want
+ to use this option. (default: 1, only available
+ with ``CONFIG_I8K``)
+
+* power_status:bool
+ Report AC status in ``/proc/i8k``. (default: 0,
+ only available with ``CONFIG_I8K``)
+
+* fan_mult:uint
+ Factor to multiply fan speed with. (default:
+ autodetect)
+
+* fan_max:uint
+ Maximum configurable fan speed. (default:
+ autodetect)
+
+Legacy ``/proc`` interface
+--------------------------
+
+.. warning:: This interface is obsolete and deprecated and should not
+ used in new applications. This interface is only
+ available when kernel is compiled with option
+ ``CONFIG_I8K``.
+
+The information provided by the kernel driver can be accessed by
+simply reading the ``/proc/i8k`` file. For example::
+
+ $ cat /proc/i8k
+ 1.0 A17 2J59L02 52 2 1 8040 6420 1 2
+
+The fields read from ``/proc/i8k`` are::
+
+ 1.0 A17 2J59L02 52 2 1 8040 6420 1 2
+ | | | | | | | | | |
+ | | | | | | | | | +------- 10. buttons status
+ | | | | | | | | +--------- 9. AC status
+ | | | | | | | +-------------- 8. fan0 RPM
+ | | | | | | +------------------- 7. fan1 RPM
+ | | | | | +--------------------- 6. fan0 status
+ | | | | +----------------------- 5. fan1 status
+ | | | +-------------------------- 4. temp0 reading (Celsius)
+ | | +---------------------------------- 3. Dell service tag (later known as 'serial number')
+ | +-------------------------------------- 2. BIOS version
+ +------------------------------------------ 1. /proc/i8k format version
+
+A negative value, for example -22, indicates that the BIOS doesn't
+return the corresponding information. This is normal on some
+models/BIOSes.
+
+For performance reasons the ``/proc/i8k`` doesn't report by default
+the AC status since this SMM call takes a long time to execute and is
+not really needed. If you want to see the ac status in ``/proc/i8k``
+you must explictitly enable this option by passing the
+``power_status=1`` parameter to insmod. If AC status is not
+available -1 is printed instead.
+
+The driver provides also an ioctl interface which can be used to
+obtain the same information and to control the fan status. The ioctl
+interface can be accessed from C programs or from shell using the
+i8kctl utility. See the source file of ``i8kutils`` for more
+information on how to use the ioctl interface.
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 230ad59b462b..092435ad6bb8 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -44,6 +44,7 @@ Hardware Monitoring Kernel Drivers
coretemp
da9052
da9055
+ dell-smm-hwmon
dme1737
ds1621
ds620
--
2.24.0
On Tue, 19 Nov 2019 14:49:21 +0100
Giovanni Mascellani <[email protected]> wrote:
> Part of the documentation is taken from the README of the userspace
> utils (https://github.com/vitorafsr/i8kutils). The license is GPL-2+
> and the author Massimo Dal Zotto is already credited as author of
> the module. Therefore there should be no copyright problem.
Given that you know the details, could you maybe put an SPDX tag at the
top with the licensing information?
Otherwise looks good.
Thanks,
jon