On Tuesday 13 May 2008, Matthew Garrett wrote:
> Fix Linux to conform to 11.3.18 of the ACPI spec 3.0. In the absence of
> a _TZP method, we should be polling at a default frequency. While it can
> be argued that "0" is a default frequency, I don't think that's what the
> spec authors had in mind.
Actually it is what the spec authors had in mind,
and the spec is wrong. Yes, I can provide documentation
supporting this statement.
NAK
thanks,
-Len
> Signed-off-by: Matthew Garrett <mjg@xxxxxxxxxx>
>
> ---
>
> Arguably this should be implemented in such a way that the polling rate
> increases as the temperature rises and drops if the trend is downwards.
> That would give higher resolution when we're heading towards a trip
> point, without any significant increase in power consumption since
> increased temperatures imply that the CPU is probably not idle.
>
> diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
> index 504385b..93cb3e8 100644
> --- a/drivers/acpi/thermal.c
> +++ b/drivers/acpi/thermal.c
> @@ -846,10 +846,11 @@ static void acpi_thermal_check(void *data)
> * Calculate Sleep Time
> * --------------------
> * If we're in the passive state, use _TSP's value. Otherwise
> - * use the default polling frequency (e.g. _TZP). If no polling
> - * frequency is specified then we'll wait forever (at least until
> - * a thermal event occurs). Note that _TSP and _TZD values are
> - * given in 1/10th seconds (we must covert to milliseconds).
> + * use the default polling frequency (e.g. _TZP). If no
> + * polling frequency is specified then we'll wait 10 seconds
> + * (or until a thermal event occurs). Note that _TSP and _TZD
> + * values are given in 1/10th seconds (we must covert to
> + * milliseconds).
> */
> if (tz->state.passive) {
> sleep_time = tz->trips.passive.tsp * 100;
> @@ -1575,8 +1576,9 @@ static int acpi_thermal_get_info(struct acpi_thermal *tz)
> /* Get default polling frequency [_TZP] (optional) */
> if (tzp)
> tz->polling_frequency = tzp;
> - else
> - acpi_thermal_get_polling_frequency(tz);
> + else if (acpi_thermal_get_polling_frequency(tz) == -ENODEV)
> + /* If no _TZP, default to polling every 10 seconds */
> + tz->polling_frequency = 100;
>
> return 0;
> }
>
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