Re: Feedback on hardware support for Odroid U3

[Krzysztof Kozlowski <k.kozlowski.k@gmail.com>]

W dniu 13.06.2015 o 18:11, Thomas-Karl Pietrowski pisze:
> Am Samstag, 13. Juni 2015, 15:09:32 schrieb Krzysztof Kozlowski:
>> W dniu 12.06.2015 o 22:53, Thomas Pietrowski pisze:
>>> Hello again,
>>>
>>> first after fixing my booting problems I now get different warnings after
>>> boot. - config: http://pastebin.com/MHUu51pF
>>> - log: http://pastebin.com/9YMgMmFL
>>> - repo: arm-soc
>>> I read the last days that you are still working on the clk drivers, so
>>> as these warnings appear to be related to that you might be interested
>>> on them.
>>
>> You mean the warnings on clocks (starting from runtime PM and FIMC)? I
>> hit them also on Trats2. Just need to find a person (or time) who will
>> fix it...
>>
> Ok then. I just don't remember that I had them when using 3.19.x code by 
> Tobias Jakobi before. I'll test his latest code later. The reason I wanted to 
> use code from arm-soc is that I thought his changes/patches are already here 
> after two linux releases. However, in the past the CPU fan wasn't working at 
> all (0 RPM) and /sys/class/thermal/[...]/temp reported more than 70°C (was 
> compiling a newer kernel code at this moment). Don't believe it was healthy.
> 
>>> Additionally my CPU fan it running at full RPM all the time. I checked
>>> the temperature just to be sure and it says it's 20°C. Is this problem
>>> known or can I help debugging it?
>>
>> After quick look at DTS, I think that on Exynos4412 Odroid family there
>> is no fan defined. No fan so cooling is done only through CPU
>> frequencies. The fan probably works on default setting from bootloader
>> or default register values.
>>
> Just something at this point which comes to my mind. Imagine we have the fan 
> regulation/driver working. What happens when we simply disconnect the fan and 
> the CPU hits higher temperatures? Will it still work on high frequencies or 
> will it self-protect by using lower CPU frequencies?

I do not know how the thermal/cooler driver works. I suppose it depends
whether cooling device (the pwm-fan) reports non-working fan. You should
rather ask on linux-pm@vger.kernel.org mailing list. That is the place
for thermal framework.

> CPU throttling and CPU cooling should be two seperate processes, isn't it?

Although cpu frequency driver is a separate thing but for cooling it
behaves like a cooling device. A fan can be a cooling device. CPU
frequency as well.

> 
>> The stock Odroid U3 has only passive cooler.
>>
> That's true, but they (hardkernel) also sell a optional fan and the socket for 
> is is still there when buying the board.
> See, 
> http://www.hardkernel.com/main/products/prdt_info.php?g_code=G138760358261 for 
> the optional fan.
> Therefore, it is not a hardware hack or whatever.

Right.

> 
>> Probably support for fan could be added... If you would like to take
>> care of it, go for it! :)
>>
> I just browsed Tobias Jakobi's "linux-odroid" repository at github and found 
> out, that work is already made on that by people at Samsung :)
> https://github.com/tobiasjakobi/linux-odroid/commit/a2236c8f74321357e505be0a054032325a7e3a5d
> Hopefully both are also in this mailing list and interested in getting this 
> upstream. In the mean time I'll test it based on tobiasjakobi's codebase 
> again.


I wonder why this is not in mainline... Or maybe it is?

Best regards,
Krzysztof