Re: Binding together tegradrm & nvhost

[Mark Zhang <markz-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On Tue, 2012-08-21 at 14:35 +0800, Terje Bergström wrote:
> On 21.08.2012 09:12, Mark Zhang wrote:
> > OK, thank you. In current version, all devices are created by
> > "of_platform_populate" in board init function. So if we still need to
> > define devices in dt, what's the benefit that we put these device
> > creation works into host1x's probe function? I don't see any difference
> > although create device in host1x probe() sounds more reasonable...
> 
> Until I have managed to integrate nvhost to tegradrm, the devices
> creation should be done as it is done now. With nvhost, we will need
> extra data per device, so we'll need to create the devices in nvhost.
> 

OK. Thank you.

> > OK. So we have fence to sync all operations on a specific buffer. So
> > this also means we should add fence support on GEM and dma-buf
> > implementation both, right?
> 
> We'll have fences for operations, not buffers. User space must figure
> out that if operation that reads from/writes to buffer is complete, the
> buffer is ready to be reused.
> Discussion in mm-sig attaches fences to buffers, which would cause a lot
> of synchronization logic being added to kernel. Each operation can work
> on multiple buffers, some in read-only, some in read-write, some in
> write-only mode, so we'd end up returning an array of fences in a
> complicated structure.
> 

OK. I'll have a look at discussions in mm-sig.

> It's simpler if kernel just knows when operation ends, and lets user
> space take care of the complexity.
> 
> Terje
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