On Tuesday, October 04, 2016 01:51:40 PM Srinivas Pandruvada wrote:
> 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");
>
Applied.
Thanks,
Rafael
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