Commit bea2d986 authored by Srinivas Pandruvada's avatar Srinivas Pandruvada Committed by Rafael J. Wysocki
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ACPI: fan: Properly handle fine grain control 



When _FIF object specifies support for fine grain control, then fan speed
can be set from 0 to 100% with the recommended minimum "step size" via
_FSL object. Here the control value doesn't need to match any value from
_FPS object.

Currently we have a simple solution implemented which just pick maximum
control value from _FPS to display the actual state, but this is not
optimal when there is a big window between two control values in
_FPS. Also there is no way to set to any speed which doesn't match
control values in _FPS. The system firmware can start the fan at speed
which doesn't match any control value.

To support fine grain control (when supported) via thermal sysfs:
- cooling device max state is not _FPS state count but it will be
100 / _FIF.step_size
Step size can be from 1 to 9.
- cooling device current state is _FST.control / _FIF.step_size
- cooling device set state will set the control value
cdev.curr_state * _FIF.step_size plus any adjustment for 100%.
By the spec, when control value do not sum to 100% because of
_FIF.step_size, OSPM may select an appropriate ending Level increment
to reach 100%.

There is no rounding during calculation. For example if step size
is 6:
thermal sysfs cooling device max_state = 100/6 = 16
So user can set any value from 0-16.

If the system boots with a _FST.control which is not multiples
of step_size, the thermal sysfs cur_state will be based on the
range. For example for step size = 6:
_FST.control	thermal sysfs cur_state
------------------------------------------------
0-5		0
6-11		1
..
..
90-95		15
96-100		16

While setting the _FST.control, the compensation will be at
the last step for cur_state = 16, which will set the _FST.control
to 100.

Signed-off-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent d445571f

drivers/acpi/fan.h

+6 −0
Original line number Diff line number Diff line
@@ -36,6 +36,12 @@ struct acpi_fan_fif { 
	u8 low_speed_notification;

};



struct acpi_fan_fst {

	u64 revision;

	u64 control;

	u64 speed;

};



struct acpi_fan {

	bool acpi4;

	struct acpi_fan_fif fif;

drivers/acpi/fan_core.c

+68 −26
Original line number Diff line number Diff line
@@ -63,20 +63,24 @@ static int fan_get_max_state(struct thermal_cooling_device *cdev, unsigned long 
	struct acpi_device *device = cdev->devdata;

	struct acpi_fan *fan = acpi_driver_data(device);



	if (fan->acpi4)

		*state = fan->fps_count - 1;

	if (fan->acpi4) {

		if (fan->fif.fine_grain_ctrl)

			*state = 100 / fan->fif.step_size;

		else

			*state = fan->fps_count - 1;

	} else {

		*state = 1;

	}



	return 0;

}



static int fan_get_state_acpi4(struct acpi_device *device, unsigned long *state)

static int acpi_fan_get_fst(struct acpi_device *device, struct acpi_fan_fst *fst)

{

	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

	struct acpi_fan *fan = acpi_driver_data(device);

	union acpi_object *obj;

	acpi_status status;

	int control, i;

	int ret = 0;



	status = acpi_evaluate_object(device->handle, "_FST", NULL, &buffer);

	if (ACPI_FAILURE(status)) {
@@ -89,35 +93,52 @@ static int fan_get_state_acpi4(struct acpi_device *device, unsigned long *state) 
	    obj->package.count != 3 ||

	    obj->package.elements[1].type != ACPI_TYPE_INTEGER) {

		dev_err(&device->dev, "Invalid _FST data\n");

		status = -EINVAL;

		ret = -EINVAL;

		goto err;

	}



	control = obj->package.elements[1].integer.value;

	fst->revision = obj->package.elements[0].integer.value;

	fst->control = obj->package.elements[1].integer.value;

	fst->speed = obj->package.elements[2].integer.value;



err:

	kfree(obj);

	return ret;

}



static int fan_get_state_acpi4(struct acpi_device *device, unsigned long *state)

{

	struct acpi_fan *fan = acpi_driver_data(device);

	struct acpi_fan_fst fst;

	int status, i;



	status = acpi_fan_get_fst(device, &fst);

	if (status)

		return status;



	if (fan->fif.fine_grain_ctrl) {

		/* This control should be same what we set using _FSL by spec */

		if (fst.control > 100) {

			dev_dbg(&device->dev, "Invalid control value returned\n");

			goto match_fps;

		}



		*state = (int) fst.control / fan->fif.step_size;

		return 0;

	}



match_fps:

	for (i = 0; i < fan->fps_count; i++) {

		/*

		 * When Fine Grain Control is set, return the state

		 * corresponding to maximum fan->fps[i].control

		 * value compared to the current speed. Here the

		 * fan->fps[] is sorted array with increasing speed.

		 */

		if (fan->fif.fine_grain_ctrl && control < fan->fps[i].control) {

			i = (i > 0) ? i - 1 : 0;

		if (fst.control == fan->fps[i].control)

			break;

		} else if (control == fan->fps[i].control) {

			break;

		}

	}

	if (i == fan->fps_count) {

		dev_dbg(&device->dev, "Invalid control value returned\n");

		status = -EINVAL;

		goto err;

		return -EINVAL;

	}



	*state = i;



err:

	kfree(obj);

	return status;

}
@@ -161,12 +182,27 @@ static int fan_set_state_acpi4(struct acpi_device *device, unsigned long state) 
{

	struct acpi_fan *fan = acpi_driver_data(device);

	acpi_status status;

	u64 value = state;

	int max_state;



	if (state >= fan->fps_count)

	if (fan->fif.fine_grain_ctrl)

		max_state = 100 / fan->fif.step_size;

	else

		max_state = fan->fps_count - 1;



	if (state > max_state)

		return -EINVAL;



	status = acpi_execute_simple_method(device->handle, "_FSL",

					    fan->fps[state].control);

	if (fan->fif.fine_grain_ctrl) {

		value *= fan->fif.step_size;

		/* Spec allows compensate the last step only */

		if (value + fan->fif.step_size > 100)

			value = 100;

	} else {

		value = fan->fps[state].control;

	}



	status = acpi_execute_simple_method(device->handle, "_FSL", value);

	if (ACPI_FAILURE(status)) {

		dev_dbg(&device->dev, "Failed to set state by _FSL\n");

		return -ENODEV;
@@ -238,6 +274,12 @@ static int acpi_fan_get_fif(struct acpi_device *device) 
	fan->fif.step_size = fields[2];

	fan->fif.low_speed_notification = fields[3];



	/* If there is a bug in step size and set as 0, change to 1 */

	if (!fan->fif.step_size)

		fan->fif.step_size = 1;

	/* If step size > 9, change to 9 (by spec valid values 1-9) */

	else if (fan->fif.step_size > 9)

		fan->fif.step_size = 9;

err:

	kfree(obj);

	return status;