Messages in this thread | | | Subject | Re: DMA-buf and uncached system memory | From | Thomas Zimmermann <> | Date | Mon, 15 Feb 2021 13:00:46 +0100 |
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Hi
Am 15.02.21 um 10:49 schrieb Thomas Zimmermann: > Hi > > 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.
Re-reading this paragrah, it sounds more as if you want to let the exporter know where to move the buffer. Is this another case of the missing-pin-flag problem?
Best regards Thomas
>> >> 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? > > For vmap operations, we return the address as struct dma_buf_map, which > contains additional information about the memory buffer. In vram > helpers, we have the interface drm_gem_vram_offset() that returns the > offset of the GPU device memory. > > Would it be feasible to combine both concepts into a dma-buf interface > that returns the device-memory offset plus the additional caching flag? > > There'd be a structure and a getter function returning the structure. > > struct dma_buf_offset { > bool cached; > u64 address; > }; > > // return offset in *off > int dma_buf_offset(struct dma_buf *buf, struct dma_buf_off *off); > > Whatever settings are returned by dma_buf_offset() are valid while the > dma_buf is pinned. > > 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@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > 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: Felix Imendörffer
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