[PATCH 0/6] Add CPU Frequency scaling support on Armada 37xx

[Andre Heider]

On 18/12/17 18:03, Gregory CLEMENT wrote:
> Hi Andre,
>   
>   On mer., déc. 06 2017, Andre Heider <a.heider at gmail.com> wrote:
> 
>> On 06/12/17 12:50, Gregory CLEMENT wrote:
>>> I did a last rebase before sending the series to remove the avs part not
>>> working yet. And during this rebase I introduced an bug.
>>>
>>> I will send a v2 soon if  you are intersected by testing it right now,
>>> here it is the fix:
>>>
>>> iff --git a/drivers/cpufreq/armada-37xx-cpufreq.c b/drivers/cpufreq/armada-37xx-cpufreq.c
>>> index 40c9a744cc6e..96c2600009b5 100644
>>> --- a/drivers/cpufreq/armada-37xx-cpufreq.c
>>> +++ b/drivers/cpufreq/armada-37xx-cpufreq.c
>>> @@ -219,7 +219,8 @@ static int __init armada37xx_cpufreq_driver_init(void)
>>>            */
>>>           for (load_level = ARMADA_37XX_DVFS_LOAD_0; load_level < LOAD_LEVEL_NR;
>>>                load_level++) {
>>> -               unsigned long freq = dvfs->divider[load_level];
>>> +               unsigned long freq = cur_frequency /
>>> +                       dvfs->divider[load_level];
>>>                     ret = dev_pm_opp_add(cpu_dev, freq, 0);
>>>                   if (ret)
>>
>> Much better, that seems to work so far, thanks!
>>
>> My espressobin now gets these frequencies: 200 MHz, 250 MHz, 500 MHz
>> and 1000 MHz.
>>
>> With the schedutil governor and `watch -n 0.2 cpufreq-info -f -m` it
>> jumps over all of those depending on the load, nice:
>>
>> Tested-by: Andre Heider <a.heider at gmail.com>
>>
>> The measured power usage doesn't drop though, I guess that requires
>> the AVS part you mentioned? Looking forward to it ;)
> 
> Well I did some measurement and i saw some drop, according to my notes:
> 
> @ 250MHz: 222mA at 12V => 2.66W
> @ 1000MHz: 238mA at 12CV => 2.87W
> 
> Not something huge, but only the CPUs which are concerned so it's not so
> bad.

Oh, okay, my cheap equipment isn't capable to measure a difference of 
just 0.2w... Guess I was hoping for more ;)

>> On a related note: Do you know if power usage can be lowered by
>> disabling eth phys? Is that possible on mainline?
> 
> For the test I have done just by removing an Ethernet cable we save a
> lot of power, so it helps. I'm sure it is doable on mainline, but maybe
>   currently, there is something still missing.

Promising, was that with a downstream kernel?

Thanks,
Andre