Le lundi 15 février 2021 à 09:58 +0100, Christian König a écrit : > 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? Hopefully I'm getting this right, but this makes me think of a long standing issue I've met with Intel DRM and UVC driver. If I let the UVC driver allocate the buffer, and import the resulting DMABuf (cacheable memory written with a cpu copy in the kernel) into DRM, we can see cache artifact being displayed. While if I use the DRM driver memory (dumb buffer in that case) it's clean because there is a driver specific solution to that. There is no obvious way for userspace application to know what's is right/wrong way and in fact it feels like the kernel could solve this somehow without having to inform userspace (perhaps). > > After all the system memory access pattern is a PCIe extension and as > such something generic. > > Regards, > Christian.
