On Fri, 25 Jan 2019 at 12:30, Christian König <[email protected]> wrote: > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher <[email protected]> wrote: > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > >> <[email protected]> wrote: > >>> 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]>. > >>>> > >> Same: > >> Reviewed-by: Alex Deucher <[email protected]> > >> > > Thanks all > > > > Should I resend the patch with the subject corrected? > > I will update the subject line and push it upstream through > drm-misc-next if nobody objects. >
Wonderful, thanks.
