Re: Feedback on hardware support for Odroid U3

[Thomas-Karl Pietrowski <thopiekar@gmail.com>]

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

> 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.

> 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.

Regards,
Thomas