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thermal: rcar-thermal: update thermal zone only when temperature changes

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Avoid updating the thermal zone in case an IRQ was triggered but the
temperature didn't effectively change.
Note this is not a driver issue.
Below is a captured debug trace illustrating the purpose of this patch:
out of 8 thermal zone updates, only 2 are actually necessary.

[   41.120000] rcar_thermal_work(): cctemp=25000
[   41.120000] rcar_thermal_work(): nctemp=30000
[   41.120000] rcar_thermal_work(): temp is now 30000C, update thermal zone
[   58.990000] rcar_thermal_work(): cctemp=30000
[   58.990000] rcar_thermal_work(): nctemp=30000
[   58.990000] rcar_thermal_work(): same temp, do not update thermal zone
[   59.290000] rcar_thermal_work(): cctemp=30000
[   59.290000] rcar_thermal_work(): nctemp=30000
[   59.290000] rcar_thermal_work(): same temp, do not update thermal zone
[   59.590000] rcar_thermal_work(): cctemp=30000
[   59.590000] rcar_thermal_work(): nctemp=30000
[   59.590000] rcar_thermal_work(): same temp, do not update thermal zone
[   59.890000] rcar_thermal_work(): cctemp=30000
[   59.890000] rcar_thermal_work(): nctemp=30000
[   59.890000] rcar_thermal_work(): same temp, do not update thermal zone
[   60.190000] rcar_thermal_work(): cctemp=30000
[   60.190000] rcar_thermal_work(): nctemp=30000
[   60.190000] rcar_thermal_work(): same temp, do not update thermal zone
[   60.490000] rcar_thermal_work(): cctemp=30000
[   60.490000] rcar_thermal_work(): nctemp=30000
[   60.490000] rcar_thermal_work(): same temp, do not update thermal zone
[   60.790000] rcar_thermal_work(): cctemp=30000
[   60.790000] rcar_thermal_work(): nctemp=35000
[   60.790000] rcar_thermal_work(): temp is now 35000C, update thermal zone

I suspect this may be due to sensor sampling accuracy / fluctuation,
but no formal proof.

Signed-off-by: Patrick Titiano <ptitiano@baylibre.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
This commit is contained in:
Patrick Titiano 2014-02-28 14:10:04 +01:00 committed by Zhang Rui
parent 206c0cba09
commit 9477165ec5
1 changed files with 6 additions and 1 deletions
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5
drivers/thermal/rcar_thermal.c
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@ -299,11 +299,16 @@ static void _rcar_thermal_irq_ctrl(struct rcar_thermal_priv *priv, int enable)
static void rcar_thermal_work(struct work_struct *work)
{
struct rcar_thermal_priv *priv;
unsigned long cctemp, nctemp;
priv = container_of(work, struct rcar_thermal_priv, work.work);
rcar_thermal_get_temp(priv->zone, &cctemp);
rcar_thermal_update_temp(priv);
rcar_thermal_irq_enable(priv);
rcar_thermal_get_temp(priv->zone, &nctemp);
if (nctemp != cctemp)
thermal_zone_device_update(priv->zone);
}