[Mactel-linux-devel] AppleTV issues

[Scott D. D. <da...@4p...>]

I'm working on cleaning up various AppleTV issues. I'm running the 
mythic-beasts boot method under a 2.6.21.5 kernel with the AppleTV 
and MacTel patches. The target is a standalone MythTV frontend able 
to handle both SD and HD content. So far things are looking good, 
with nvidia xvmc hardware decode, the AppleTV platform as sufficient 
power to decode 1080i with 30 percent idle left over. There are some 
issues that cause problems so the solution is not complete.

1) 	The network interface gets a large amount of overrun errors 
when viewing HD content, I've tracked this down to the AppleTV cpu 
running about 90 percent of the time in C3 state even with cpu at 70 
percent. In C3 state, the response to interrupts is about 50 times 
longer which results in network overrun errors. If I disable 
processor.ko (acpi processor control), then I don't get network 
errors. Naturally, some would say just run it this way but that's a 
hack and I want to understand why it's sticking in C3 and never going 
to C1, then fix the problem. The ability to idle down in power when 
truly idle is important in this application.
	From what I gather, most cpu power state problems are with 
the inability to get to C3 for laptop battery life. This is the 
reverse, I'm stuck in C3 with 10 percent usage in C2.

2)	The pci-express root port/nvidia are running at X2 link 
width. Under the AppleTV OSX, this link width is X16. So somehow the 
pci-express link width gets limited to 2X width under linux but not 
under OSX. Naturally this link width is important in mpeg2 decode 
application especially when decoding HD content. My suspicion is that 
this is somehow also related to being stuck in C3 power state. The 
link width negotiation is handled by the two chipsets and it does not 
see that the cpu is involved but maybe C3 power state also extends to 
the chips sets.

Any suggestions or help would be appreciated.

Scott