Re: DMA-buf and uncached system memory

[Thomas Zimmermann]

Hi

Am 23.06.22 um 10:26 schrieb Christian König:
> Am 23.06.22 um 10:13 schrieb Thomas Zimmermann:
> > Hi Christian
> >
> > Am 15.02.21 um 09:58 schrieb Christian König:
> > > Hi guys,
> > >
> > > we are currently working an Freesync and direct scan out from system 
> > > memory on AMD APUs in A+A laptops.
> > >
> > > On problem we stumbled over is that our display hardware needs to 
> > > scan out from uncached system memory and we currently don't have a 
> > > way to communicate that through DMA-buf.
> > >
> > > For our specific use case at hand we are going to implement something 
> > > driver specific, but the question is should we have something more 
> > > generic for this?
> >
> > I had a patchset here that extends iosys-map (former dma-buf-map) with 
> > caching information. I'll post a copy.
>
> Oh, nice. But why on iosys-map? We need that per DMA-buf.

It's returned via the dma-buf's vmap call within the iosys-map 
structure. If the dma-buf moves, the following vmap calls always return 
updated caching information. Maybe it's not quite what you need for 
Freesync?

I'll use this for format-conversion helpers, which do some optimizations 
for uncached memory.

Anyway, I have to look for that patch...

Best regards
Thomas

> Thanks,
> Christian.
>
> > Sorry for being late to reply.
> >
> > Best regards
> > Thomas
> >
> > > After all the system memory access pattern is a PCIe extension and as 
> > > such something generic.
> > >
> > > Regards,
> > > Christian.
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

Attachment: OpenPGP_signature
Description: OpenPGP digital signature