RFC: Radeon multi ring support branch

[Alex Deucher]

2011/11/17 Christian König <deathsimple at vodafone.de>:
> 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.

I've got a few other patches to enable further functionality in the
mring patches.
- per ring fence interrupts
- add some additional ring fields to better handle different ring types

http://people.freedesktop.org/~agd5f/mrings/

Alex