On Thu, 24 Jan 2019 at 13:31, Koenig, Christian <[email protected]> wrote: > > Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > The DRM driver stack is designed to work with cache coherent devices > > only, but permits an optimization to be enabled in some cases, where > > for some buffers, both the CPU and the GPU use uncached mappings, > > removing the need for DMA snooping and allocation in the CPU caches. > > > > The use of uncached GPU mappings relies on the correct implementation > > of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > will use cached mappings nonetheless. On x86 platforms, this does not > > seem to matter, as uncached CPU mappings will snoop the caches in any > > case. However, on ARM and arm64, enabling this optimization on a > > platform where NoSnoop is ignored results in loss of coherency, which > > breaks correct operation of the device. Since we have no way of > > detecting whether NoSnoop works or not, just disable this > > optimization entirely for ARM and arm64. > > > > Cc: Christian Koenig <[email protected]> > > Cc: Alex Deucher <[email protected]> > > Cc: David Zhou <[email protected]> > > Cc: Huang Rui <[email protected]> > > Cc: Junwei Zhang <[email protected]> > > Cc: Michel Daenzer <[email protected]> > > Cc: David Airlie <[email protected]> > > Cc: Daniel Vetter <[email protected]> > > Cc: Maarten Lankhorst <[email protected]> > > Cc: Maxime Ripard <[email protected]> > > Cc: Sean Paul <[email protected]> > > Cc: Michael Ellerman <[email protected]> > > Cc: Benjamin Herrenschmidt <[email protected]> > > Cc: Will Deacon <[email protected]> > > Cc: Christoph Hellwig <[email protected]> > > Cc: Robin Murphy <[email protected]> > > Cc: amd-gfx list <[email protected]> > > Cc: dri-devel <[email protected]> > > Reported-by: Carsten Haitzler <[email protected]> > > Signed-off-by: Ard Biesheuvel <[email protected]> > > The subject line should probably read "disable uncached...". >
Ugh, of course ... > With that fixed the patch is Reviewed-by: Christian König > <[email protected]>. > Thanks. _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
