Hello Krzysztof,

On 02/11/2017 05:14 PM, Krzysztof Kozlowski wrote:

In Odroid XU3 Lite board, the temperature levels reported for thermal
zone 0 were weird. In warm room:
	/sys/class/thermal/thermal_zone0/temp:32000
	/sys/class/thermal/thermal_zone1/temp:51000
	/sys/class/thermal/thermal_zone2/temp:55000
	/sys/class/thermal/thermal_zone3/temp:54000
	/sys/class/thermal/thermal_zone4/temp:51000

Sometimes after booting the value was even equal to ambient temperature
which is highly unlikely to be a real temperature of sensor in SoC.

The thermal sensor's calibration (trimming) is based on fused values.
In case of the board above, the fused values are: 35, 52, 43, 58 and 43
(corresponding to each TMU device).  However driver defined a minimum value
for fused data as 40 and for smaller values it was using a hard-coded 55
instead.  This lead to mapping data from sensor to wrong temperatures
for thermal zone 0.

Various vendor 3.10 trees (Hardkernel's based on Samsung LSI, Artik 10)
do not impose any limits on fused values.  Since we do not have any
knowledge about these limits, use 0 as a minimum accepted fused value.
This should essentially allow accepting any reasonable fused value thus
behaving like vendor driver.

The exynos5420-tmu-sensor-conf.dtsi is copied directly from existing
exynso4412 with one change - the samsung,tmu_min_efuse_value.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

---

Testing on other Exynos542x boards is much appreciated. Especially I
wonder what efuse values are there.

I tested on both Exynos5422 Odroid XU4 and Exynos5800 Peach Pi boards.

The temperatures levels reported for these two boards on a warm room are:

Odroid XU4

# cat /sys/class/thermal/thermal_zone*/temp
50000
50000
54000
51000
48000

Peach Pi

# cat /sys/class/thermal/thermal_zone*/temp
42000
44000
27000 <-- weird value for thermal zone 2 like zone 0 in your XU3 lite
45000
45000

And the efuse values for the TMU devices are:

Odroid XU4

TMU0 = 45
TMU1 = 44
TMU2 = 44
TMU3 = 46
TMU3 = 46

Peach Pi

TMU0 = 44
TMU1 = 46
TMU2 = 36
TMU3 = 53
TMU3 = 46

The fused value for TMU2 is < 40 so that explains the weird temperature
level for thermal zone 2 in Peach. So after your patch, makes more sense:

# cat /sys/class/thermal/thermal_zone*/temp
41000
42000
45000
43000
43000

I wonder though if 0 is the best value or if we should just lower more
to cover the used e-fuse values in Exynos5 boards. But as you said,
we have no knowledge about these limits...

Reviewed-by: Javier Martinez Canillas <redacted>
Tested-by: Javier Martinez Canillas <redacted>

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America