Re: [PATCH] drm/radeon/kms: prevent parallel AtomBIOS calls

[Jerome G. <gl...@fr...>]

On Thu, Dec 17, 2009 at 12:04:02AM +0100, Rafał Miłecki wrote:
> In future we will execute AtomBIOS commands from contexts (like power
> management) so we need to make sure we won't execute two commands at
> same time to prevent locking up GPU.
> 
> With this patch applied Sedat Dilek (RV515) was able to finally test
> my PM patch. Also tested on my RV620.
> 
> -- 
> Rafał

I am in favor of a different approach, using a r/w lock and
taking the lock in read in all path, and write in powermanager
& init path. Doc state that we need exclusive access to GPU
while doing PM stuff. Thus r/w lock sounds like what we want
to do. Should be hard to add that to ioctl & modesetting callback.

Never the less this patch might be usefull, as for instance
we might be doing modesetting at the same time on 2 different
head of an avivo gpu and this might lead to // execution of
atombios and it's my understanding that atombios code is not
safe in this regards.

Cheers,
Jerome