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@xxxxxxxxxxxxxxx>
---
drivers/acpi/fan.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/acpi/fan.c b/drivers/acpi/fan.c
index 384cfc3..f34859a 100644
--- a/drivers/acpi/fan.c
+++ b/drivers/acpi/fan.c
@@ -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");
--
2.7.4
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