Replicant 4.0: GTA04-Kernel

[Paul Kocialkowski]

Le mercredi 10 juillet 2013 à 21:19 +0200, Dr. H. Nikolaus Schaller a
écrit :
> Hi,
> I am now successful to compile Replicant 2.3 and 4.0 (on Darwin / OS X) and the resulting systems run on the GTA04 board.
> It needs some special considerations for setting up the host toolchain and one patch of the source tree (for 2.3 only).

Nice. Keep in mind that we more or less dropped Replicant 2.3 as of now.
All of the new development will happen for Replicant 4.0, especially
regarding GTA04.

> What I am wondering and trying to understand is why Replicant 4.0 uses an apparently older kernel.
> I.e.
> 
> 2.3 => 3.2.21
> 4.0 => 3.0.78

Basically, the 3.2 kernel was the result of an unofficial 3.2 kernel
from linaro merged with neil's 3.2-gta04 branch. It was sort of working
but the inevitable suspend/resume issues were there.

So we tried an incredible amount of different kernel combinations and
none of them really fully worked. This is why I think we need to settle
down (hopefully with your help) on what is better and what gives us our
best shot at having a really working kernel on gta04.

3.0 was chosen because it was set by Google to be the kernel revision to
use for the ICS userspace. The ICS userspace also contains backwards
compatibility for older kernels, such as the 2.6.37 kernel used by
Rowboat.

> So maybe someone can explain since I thought that the 2.3 kernel should be at least a good basis for Replicant 4.0
> and/or 4.0 should have a newer kernel.

Frankly, it is not a good basis at all. What is really important to have
is proper power managment, most of the rest can be added without much
effort and is possible on any kernel. And the 3.2 kernel lacks proper
power management and it is the result of a "dirty merge", so we'd better
start off on a cleaner base.

I am nearly done with what I wanted to do for the Galaxy S3, so I will
focus on gta04 starting on Monday. I truly hope we can find a solution
for the kernel issue before September.

> And just as a side-note: it appears that the BeagleBoard hackers are already running Android 4.2.2 on a 3.8 kernel:

That's worth looking into, though I doubt they care much about power
management since it's not running on battery.

I'll get back to you with concrete plans on what we can do to really
find a solution for the Replicant kernel, probably on Monday.