Commit 84baf172 authored Oct 04, 2016 by Srinivas Pandruvada Committed by Rafael J. Wysocki Oct 10, 2016

ACPI / fan: Fix error reading cur_state

On some platforms with ACPI4 variable speed fan, reading cur_state from
cooling device returns "invalid value" error. This confuses user space
applications.

This issue occurs as the current driver doesn't take account of
"FineGrainControl" from _FIF(Fan Information). When the "FineGrainControl"
is set, _FSL(FSL Set Level) takes argument as a percent, which doesn't
have to match from any control value from _FPS(Fan Performance States).
It is also possible that the Fan is not actually running at the requested
speed returning a lower speed.
On some platforms the BIOS is setting fan speed to a level during boot,
which will not have an exact match to _FPS control values. The current
implementation will treat this level as invalid value.

The simple change is to atleast return state corresponding to a maximum
control value in the _FPS compared to the current level.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent c8d2bc9b

drivers/acpi/fan.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -129,8 +129,18 @@ static int fan_get_state_acpi4(struct acpi_device device, unsigned long state)

		control = obj->package.elements[1].integer.value;
		for (i = 0; i < fan->fps_count; i++) {
		if (control == fan->fps[i].control)
		/*
		* 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;
		break;
		} else if (control == fan->fps[i].control) {
		break;
		}
		}
		if (i == fan->fps_count) {
		dev_dbg(&device->dev, "Invalid control value returned\n");

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