On 7/16/2020 6:17 AM, Thierry Reding wrote:
On Thu, Jul 16, 2020 at 01:59:33PM +0100, Jon Hunter wrote:
I also see that for gv11b we populate 'dma-coherent' and so we should
probably add this as well.
Do we know for certain that the GPU is DMA coherent? I've only tested
this (with local patches to Nouveau) without dma-coherent, so I have not
actually verified that it works without.
I vaguely recall reading that there are different apertures for sysmem,
one for coherent sysmem and another for non-coherent sysmem. So I'm not
sure if dma-coherent here will work without additional code in the
driver to ensure that all memory is allocated from the coherent sysmem
aperture.
We do have the choices of coherent and non-coherent memory accesses in
the iGPU via the two sysmem apertures. But in Tegra194 we're forcing
coherency from the memory subsystem side, so all accesses are coherent.
Terje
