dt-binding: arm/cpus.txt: fix dynamic-power-coefficient unit
The unit of dynamic-power-coefficient is described as mW/MHz/uV^2 whereas its usage in the code assumes that unit is uW/MHz/V^2 In drivers/thermal/cpu_cooling.c, the code is : power = (u64)capacitance * freq_mhz * voltage_mv * voltage_mv; do_div(power, 1000000000); which can be summarized as : power (mW) = capacitance * freq_mhz/1000 * (voltage_mv/1000)^2 or power (mW) = (capacitance * freq_mhz * (voltage_mv/1000)^2) / 1000 then power (mW) = power (uW) / 1000 so power (uW) = capacitance * freq_mhz * (voltage_mv/1000)^2 Furthermore, if we test basic values like : voltage_mv = 1000mV = 1V freq_mhz = 1000Mhz The minimum possible power, when dynamic-power-coefficient equals 1, will be with current unit: min power = 1 * 1000 * (1000000)^2 = 10^15 mW which is not realistic With the unit used by the code, the min power is min power = 1 * 1000 * 1^2 = 1000uW = 1mW which is far more realistic Signed-off-by:Vincent Guittot <vincent.guittot@linaro.org> Acked-by:
Punit Agrawal <punit.agrawal@arm.com> Acked-by:
Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by:
Rob Herring <robh@kernel.org>
parent
f858927f
Please register or sign in to comment