backport upstream commit 095151b235 (mediatek: fix pwn fan settings for
sinovoip bpi-r3 (v3))
Popular cheap PWM fans for this machine, like the ones coming in
heatsink+fan combos will not work properly at the currently defined
medium speed. Trying different pwm setting using a command
echo $value > /sys/devices/platform/pwm-fan/hwmon/hwmon1/pwm1
I found:
pwm1 value fan rotation speed cpu temperature notes
-----------------------------------------------------------------
0 maximal 31.5 Celsius too noisy
40 optimal 35.2 Celsius no noise hearable
95 minimal
above 95 does not rotate 55.5 Celsius
-----------------------------------------------------------------
Current cooling levels are:
cooling-levels = <255 96 0>;
Thus only cpu-active-high and cpu-active-low modes are usable.
This patch fixes cpu-active-medium settings for bpi-r3 board.
This patch may not be enough. Users may wants to tweak their thermal_zone0
trip points, thus tuning fan rotation speed depending on cpu temperature.
That can be done on the base of the following example:
=== example =========
# cpu temperature below 25 Celsius degrees, no rotation
echo 25000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp
# cpu temperature in [25..32] Celsius degrees, normal rotation speed
echo 32000 > /sys/class/thermal/thermal_zone0/trip_point_3_temp
# cpu temperature above 50 Celsius degrees, max rotation speed
echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_2_temp
=====================
Changes v2:
* put patch to a proper directory
* updated patch description
* tested with latest openwrt based on linux-6.6
Changes v3:
* use upstream linux patch
* update patch description
Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21252
Signed-off-by: Robert Marko <robimarko@gmail.com>
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