[Intel-gfx] [RFC] i915: make the probe asynchronous

[Daniel Vetter]

On Thu, Jul 12, 2018 at 09:29:01AM +0800, Feng Tang wrote:
> On Tue, Jun 26, 2018 at 10:29:16AM +0800, Feng Tang wrote:
> > On Mon, Jun 25, 2018 at 05:36:32PM +0200, Daniel Vetter wrote:
>  
> > Hi Daneil/Jani/Takashi,
> > 
> > When I was testing this patch from Takashi, I further checked the kernel
> > module code, and found that: we may need NOT to add any new codes to
> > prepare for i915's async probe feature!
> > 
> > Say when i915 module is being loader due to HDA's request_module() call,
> > in the callchain, do_init_module() has such code:
> > 
> >     if (!mod->async_probe_requested && (current->flags & PF_USED_ASYNC))
> >                 async_synchronize_full();
> > 
> > This will garantee the asynced probe is done before it returns.
> > 
> > I have just tested and this seems to be enough. If I am not wrong, then
> > we can take the i915 async patch directly. What do you think?
> 
> Ping for comments, thanks!

Ram (who's working on the hdcp2 code) just learned the hard way that if
i915 registration gets delayed then audio fails to load. So if you want to
make i915 fully async, then you _must_ fix the audio load stuff.

The above code just shows that if you're loading things with
request_module(), then there's not actually any async probing going on.
Which kinda defeats the point.

So yeah, I still think we need to fix this properly, or it's pointless.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch