On Thu, 7 Feb 2019 at 16:33, Alex Deucher <[email protected]> wrote: > > On Thu, Feb 7, 2019 at 10:20 AM Ard Biesheuvel > <[email protected]> wrote: > > > > On Wed, 6 Feb 2019 at 19:38, Christian König > > <[email protected]> wrote: > > > > > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel > > > > <[email protected]> wrote: > > > >> 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. > > > > Hi Christian, > > > > > > > > Are you still planning to merge this for v5.1? > > > > > > My bad, only pushed this to our internal branch, but forgot out > > > drm-misc-next. > > > > > > Fixed now, thanks for the reminder. > > > > > > > Thanks, > > > > Does anyone mind if I propose this patch for backporting to v4.19 or > > earlier once it gets merged for v5.1? > > Go for it. I was going to suggest that this should probably go to stable. >
Excellent. Note that I actually prefer sending it manually rather than let Greg or Sasha pick it up automatically, given that they are usually a bit trigger happy, i.e., patches tend to get backported before anyone has had a chance to actually check that it doesn't break anything in mainline. In other words, please don't add a cc -stable or fixes tag. I will track it myself instead. Thanks, Ard. _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
