On Fri, 25 Jan 2019 at 12:30, Christian König <ckoenig.leichtzumerken@xxxxxxxxx> wrote: > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > >> <ard.biesheuvel@xxxxxxxxxx> wrote: > >>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > >>> <Christian.Koenig@xxxxxxx> 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 <christian.koenig@xxxxxxx> > >>>>> Cc: Alex Deucher <alexander.deucher@xxxxxxx> > >>>>> Cc: David Zhou <David1.Zhou@xxxxxxx> > >>>>> Cc: Huang Rui <ray.huang@xxxxxxx> > >>>>> Cc: Junwei Zhang <Jerry.Zhang@xxxxxxx> > >>>>> Cc: Michel Daenzer <michel.daenzer@xxxxxxx> > >>>>> Cc: David Airlie <airlied@xxxxxxxx> > >>>>> Cc: Daniel Vetter <daniel@xxxxxxxx> > >>>>> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > >>>>> Cc: Maxime Ripard <maxime.ripard@xxxxxxxxxxx> > >>>>> Cc: Sean Paul <sean@xxxxxxxxxx> > >>>>> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > >>>>> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > >>>>> Cc: Will Deacon <will.deacon@xxxxxxx> > >>>>> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > >>>>> Cc: Robin Murphy <robin.murphy@xxxxxxx> > >>>>> Cc: amd-gfx list <amd-gfx@xxxxxxxxxxxxxxxxxxxxx> > >>>>> Cc: dri-devel <dri-devel@xxxxxxxxxxxxxxxxxxxxx> > >>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@xxxxxxx> > >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > >>>> The subject line should probably read "disable uncached...". > >>>> > >>> Ugh, of course ... > >>> > >>>> With that fixed the patch is Reviewed-by: Christian König > >>>> <christian.koenig@xxxxxxx>. > >>>> > >> Same: > >> Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx> > >> > > 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. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
