linux-kernel - Re: [PATCH] ACPI thermal: do not always return THERMAL_TREND

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Date:	Fri, 26 Apr 2013 14:07:45 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-acpi@...r.kernel.org, lenb@...nel.org,
	eduardo.valentin@...com
Subject: Re: [PATCH] ACPI thermal: do not always return THERMAL_TREND_RAISING for active trip points

On Friday, April 26, 2013 05:19:53 PM Zhang Rui wrote:
> Commit 4ae46befb49d4173122e0afa995c4e93d01948a2
> introduces a regression that the fan is always on
> even if the system is in idle state.
> 
> My original idea in that commit is that:
> when the current temperature is above the trip point,
> keep the fan on, even if the temperature is dropping.
> when the current temperature is below the trip point,
> turn on the fan when the temperature is raising,
> turn off the fan when the temperature is dropping.
> 
> But this is what the code actually does:
> when the current temperature is above the trip point,
> the fan keeps on.
> when the current temperature is below the trip point,
> the fan is always on because thermal_get_trend()
> in driver/acpi/thermal.c returns THERMAL_TREND_RAISING.
> Thus the fan keeps running even if the system is idle.
> 
> Fix this in drivers/acpi/thermal.c.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=56591
> https://bugzilla.kernel.org/show_bug.cgi?id=56601
> https://bugzilla.kernel.org/show_bug.cgi?id=50041#c45
> 
> Patch should be applied to 3.7 stable kernel and later.
> 
> Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> Tested-by: Matthias <morpheusxyz123@...oo.de>
> Tested-by: Ville Syrjälä <syrjala@....fi>
> Cc: <stable@...r.kernel.org> # v3.7+

Applied.

Thanks,
Rafael


> ---
>  drivers/acpi/thermal.c |   16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
> index 8470771..a33821c 100644
> --- a/drivers/acpi/thermal.c
> +++ b/drivers/acpi/thermal.c
> @@ -723,9 +723,19 @@ static int thermal_get_trend(struct thermal_zone_device *thermal,
>  		return -EINVAL;
>  
>  	if (type == THERMAL_TRIP_ACTIVE) {
> -		/* aggressive active cooling */
> -		*trend = THERMAL_TREND_RAISING;
> -		return 0;
> +		unsigned long trip_temp;
> +		unsigned long temp = KELVIN_TO_MILLICELSIUS(tz->temperature,
> +							tz->kelvin_offset);
> +		if (thermal_get_trip_temp(thermal, trip, &trip_temp))
> +			return -EINVAL;
> +
> +		if (temp > trip_temp) {
> +			*trend = THERMAL_TREND_RAISING;
> +			return 0;
> +		} else {
> +			/* Fall back on default trend */
> +			return -EINVAL;
> +		}
>  	}
>  
>  	/*
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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