RFC: Radeon multi ring support branch

[Christian König]

On 16.11.2011 01:24, Jerome Glisse wrote:
> Well as we don't specify on which value semaphore should wait on, i am 
> prety sure the first ring to increment the semaphore will unblock all 
> waiter. So if you have ring1 that want to wait on ring2 and ring3 as 
> soon as ring2 or ring3 is done ring1 will go one while either ring2 or 
> ring3 might not be done. I will test that tomorrow but from doc i have 
> it seems so. Thus it will be broken with more than one ring, that 
> would mean you have to allocate one semaphore for each ring couple you 
> want to synchronize. Note that the usual case will likely be sync btw 
> 2 ring.

Good point, but I played with it a bit more today and it is just 
behaving as I thought it would be. A single signal command will just 
unblock a single waiter, even if there are multiple waiters currently 
for this semaphore, the only thing you can't tell is which waiter will 
come first.

I should also note that the current algorithm will just emit multiple 
wait operations to a single ring, and spread the signal operations to 
all other rings we are interested in. That isn't very efficient, but 
should indeed work quite fine.

> After retesting the first patch  drm/radeon: fix debugfs handling is NAK
> a complete no go.
>
> Issue is that radeon_debugfs_cleanup is call after rdev is free. This
> is why i used a static array. I forgot about that, i should have put a
> comment. I guess you built your kernel without debugfs or that you
> didn't tested to reload the module.

Mhm, I have tested it, seen the crash, and didn't thought that this is a 
problem. Don't ask me why I can't understand it myself right now.

Anyway, I moved the unregistering of the files into a separate function, 
which is now called from radeon_device_fini instead of 
radeon_debugfs_cleanup. That seems to work fine, at least if I haven't 
missed something else.

I also merged your indention fixes and the fix for the never allocated 
semaphores and pushed the result into my public repository 
(http://cgit.freedesktop.org/~deathsimple/linux), so please take another 
look at it.

Thanks,
Christian.