Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Wed, 6 Feb 2019 at 19:38, Christian König wrote: > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel > > wrote: > >> On Fri, 25 Jan 2019 at 12:30, Christian König > >> wrote: > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: > > On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > wrote: > >> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > >> 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 > Cc: Alex Deucher > Cc: David Zhou > Cc: Huang Rui > Cc: Junwei Zhang > Cc: Michel Daenzer > Cc: David Airlie > Cc: Daniel Vetter > Cc: Maarten Lankhorst > Cc: Maxime Ripard > Cc: Sean Paul > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Will Deacon > Cc: Christoph Hellwig > Cc: Robin Murphy > Cc: amd-gfx list > Cc: dri-devel > Reported-by: Carsten Haitzler > Signed-off-by: Ard Biesheuvel > >>> The subject line should probably read "disable uncached...". > >>> > >> Ugh, of course ... > >> > >>> With that fixed the patch is Reviewed-by: Christian König > >>> . > >>> > > Same: > > Reviewed-by: Alex Deucher > > > 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? ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Thu, 7 Feb 2019 at 16:33, Alex Deucher wrote: > > On Thu, Feb 7, 2019 at 10:20 AM Ard Biesheuvel > wrote: > > > > On Wed, 6 Feb 2019 at 19:38, Christian König > > wrote: > > > > > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel > > > > wrote: > > > >> On Fri, 25 Jan 2019 at 12:30, Christian König > > > >> wrote: > > > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher > > > wrote: > > > > On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > > > wrote: > > > >> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > > >> 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 > > > Cc: Alex Deucher > > > Cc: David Zhou > > > Cc: Huang Rui > > > Cc: Junwei Zhang > > > Cc: Michel Daenzer > > > Cc: David Airlie > > > Cc: Daniel Vetter > > > Cc: Maarten Lankhorst > > > Cc: Maxime Ripard > > > Cc: Sean Paul > > > Cc: Michael Ellerman > > > Cc: Benjamin Herrenschmidt > > > Cc: Will Deacon > > > Cc: Christoph Hellwig > > > Cc: Robin Murphy > > > Cc: amd-gfx list > > > Cc: dri-devel > > > Reported-by: Carsten Haitzler > > > Signed-off-by: Ard Biesheuvel > > > >>> The subject line should probably read "disable uncached...". > > > >>> > > > >> Ugh, of course ... > > > >> > > > >>> With that fixed the patch is Reviewed-by: Christian König > > > >>> . > > > >>> > > > > Same: > > > > Reviewed-by: Alex Deucher > > > > > > > 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 dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Thu, Feb 7, 2019 at 10:20 AM Ard Biesheuvel wrote: > > On Wed, 6 Feb 2019 at 19:38, Christian König > wrote: > > > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel > > > wrote: > > >> On Fri, 25 Jan 2019 at 12:30, Christian König > > >> wrote: > > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher > > wrote: > > > On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > > wrote: > > >> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > >> 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 > > Cc: Alex Deucher > > Cc: David Zhou > > Cc: Huang Rui > > Cc: Junwei Zhang > > Cc: Michel Daenzer > > Cc: David Airlie > > Cc: Daniel Vetter > > Cc: Maarten Lankhorst > > Cc: Maxime Ripard > > Cc: Sean Paul > > Cc: Michael Ellerman > > Cc: Benjamin Herrenschmidt > > Cc: Will Deacon > > Cc: Christoph Hellwig > > Cc: Robin Murphy > > Cc: amd-gfx list > > Cc: dri-devel > > Reported-by: Carsten Haitzler > > Signed-off-by: Ard Biesheuvel > > >>> The subject line should probably read "disable uncached...". > > >>> > > >> Ugh, of course ... > > >> > > >>> With that fixed the patch is Reviewed-by: Christian König > > >>> . > > >>> > > > Same: > > > Reviewed-by: Alex Deucher > > > > > 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. Alex ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel wrote: > > On Fri, 25 Jan 2019 at 12:30, Christian König > wrote: > > > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: > > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > >> wrote: > > >>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > >>> 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 > > > Cc: Alex Deucher > > > Cc: David Zhou > > > Cc: Huang Rui > > > Cc: Junwei Zhang > > > Cc: Michel Daenzer > > > Cc: David Airlie > > > Cc: Daniel Vetter > > > Cc: Maarten Lankhorst > > > Cc: Maxime Ripard > > > Cc: Sean Paul > > > Cc: Michael Ellerman > > > Cc: Benjamin Herrenschmidt > > > Cc: Will Deacon > > > Cc: Christoph Hellwig > > > Cc: Robin Murphy > > > Cc: amd-gfx list > > > Cc: dri-devel > > > Reported-by: Carsten Haitzler > > > Signed-off-by: Ard Biesheuvel > > The subject line should probably read "disable uncached...". > > > > >>> Ugh, of course ... > > >>> > > With that fixed the patch is Reviewed-by: Christian König > > . > > > > >> Same: > > >> Reviewed-by: Alex Deucher > > >> > > > 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? Thanks, Ard. ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel wrote: On Fri, 25 Jan 2019 at 12:30, Christian König wrote: Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel wrote: On Thu, 24 Jan 2019 at 13:31, Koenig, Christian 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 Cc: Alex Deucher Cc: David Zhou Cc: Huang Rui Cc: Junwei Zhang Cc: Michel Daenzer Cc: David Airlie Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Sean Paul Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Will Deacon Cc: Christoph Hellwig Cc: Robin Murphy Cc: amd-gfx list Cc: dri-devel Reported-by: Carsten Haitzler Signed-off-by: Ard Biesheuvel The subject line should probably read "disable uncached...". Ugh, of course ... With that fixed the patch is Reviewed-by: Christian König . Same: Reviewed-by: Alex Deucher 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. Christian. Thanks, Ard. ___ amd-gfx mailing list amd-...@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Fri, 25 Jan 2019 at 12:30, Christian König wrote: > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > >> wrote: > >>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > >>> 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 > > Cc: Alex Deucher > > Cc: David Zhou > > Cc: Huang Rui > > Cc: Junwei Zhang > > Cc: Michel Daenzer > > Cc: David Airlie > > Cc: Daniel Vetter > > Cc: Maarten Lankhorst > > Cc: Maxime Ripard > > Cc: Sean Paul > > Cc: Michael Ellerman > > Cc: Benjamin Herrenschmidt > > Cc: Will Deacon > > Cc: Christoph Hellwig > > Cc: Robin Murphy > > Cc: amd-gfx list > > Cc: dri-devel > > Reported-by: Carsten Haitzler > > Signed-off-by: Ard Biesheuvel > The subject line should probably read "disable uncached...". > > >>> Ugh, of course ... > >>> > With that fixed the patch is Reviewed-by: Christian König > . > > >> Same: > >> Reviewed-by: Alex Deucher > >> > > 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@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel wrote: On Thu, 24 Jan 2019 at 13:31, Koenig, Christian 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 Cc: Alex Deucher Cc: David Zhou Cc: Huang Rui Cc: Junwei Zhang Cc: Michel Daenzer Cc: David Airlie Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Sean Paul Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Will Deacon Cc: Christoph Hellwig Cc: Robin Murphy Cc: amd-gfx list Cc: dri-devel Reported-by: Carsten Haitzler Signed-off-by: Ard Biesheuvel The subject line should probably read "disable uncached...". Ugh, of course ... With that fixed the patch is Reviewed-by: Christian König . Same: Reviewed-by: Alex Deucher 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. Christian. ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Thu, 24 Jan 2019 at 15:01, Alex Deucher wrote: > > On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > wrote: > > > > On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > 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 > > > > Cc: Alex Deucher > > > > Cc: David Zhou > > > > Cc: Huang Rui > > > > Cc: Junwei Zhang > > > > Cc: Michel Daenzer > > > > Cc: David Airlie > > > > Cc: Daniel Vetter > > > > Cc: Maarten Lankhorst > > > > Cc: Maxime Ripard > > > > Cc: Sean Paul > > > > Cc: Michael Ellerman > > > > Cc: Benjamin Herrenschmidt > > > > Cc: Will Deacon > > > > Cc: Christoph Hellwig > > > > Cc: Robin Murphy > > > > Cc: amd-gfx list > > > > Cc: dri-devel > > > > Reported-by: Carsten Haitzler > > > > Signed-off-by: Ard Biesheuvel > > > > > > The subject line should probably read "disable uncached...". > > > > > > > Ugh, of course ... > > > > > With that fixed the patch is Reviewed-by: Christian König > > > . > > > > > Same: > Reviewed-by: Alex Deucher > Thanks all Should I resend the patch with the subject corrected? ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Thu, 24 Jan 2019 at 13:31, Koenig, Christian 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 > > Cc: Alex Deucher > > Cc: David Zhou > > Cc: Huang Rui > > Cc: Junwei Zhang > > Cc: Michel Daenzer > > Cc: David Airlie > > Cc: Daniel Vetter > > Cc: Maarten Lankhorst > > Cc: Maxime Ripard > > Cc: Sean Paul > > Cc: Michael Ellerman > > Cc: Benjamin Herrenschmidt > > Cc: Will Deacon > > Cc: Christoph Hellwig > > Cc: Robin Murphy > > Cc: amd-gfx list > > Cc: dri-devel > > Reported-by: Carsten Haitzler > > Signed-off-by: Ard Biesheuvel > > The subject line should probably read "disable uncached...". > Ugh, of course ... > With that fixed the patch is Reviewed-by: Christian König > . > Thanks. ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
[PATCH] drm: enable uncached DMA optimization for ARM and arm64
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 Cc: Alex Deucher Cc: David Zhou Cc: Huang Rui Cc: Junwei Zhang Cc: Michel Daenzer Cc: David Airlie Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Sean Paul Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Will Deacon Cc: Christoph Hellwig Cc: Robin Murphy Cc: amd-gfx list Cc: dri-devel Reported-by: Carsten Haitzler Signed-off-by: Ard Biesheuvel --- include/drm/drm_cache.h | 18 ++ 1 file changed, 18 insertions(+) diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h index bfe1639df02d..97fc498dc767 100644 --- a/include/drm/drm_cache.h +++ b/include/drm/drm_cache.h @@ -47,6 +47,24 @@ static inline bool drm_arch_can_wc_memory(void) return false; #elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3) return false; +#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64) + /* +* 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. +*/ + return false; #else return true; #endif -- 2.20.1 ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel wrote: > > On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > 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 > > > Cc: Alex Deucher > > > Cc: David Zhou > > > Cc: Huang Rui > > > Cc: Junwei Zhang > > > Cc: Michel Daenzer > > > Cc: David Airlie > > > Cc: Daniel Vetter > > > Cc: Maarten Lankhorst > > > Cc: Maxime Ripard > > > Cc: Sean Paul > > > Cc: Michael Ellerman > > > Cc: Benjamin Herrenschmidt > > > Cc: Will Deacon > > > Cc: Christoph Hellwig > > > Cc: Robin Murphy > > > Cc: amd-gfx list > > > Cc: dri-devel > > > Reported-by: Carsten Haitzler > > > Signed-off-by: Ard Biesheuvel > > > > The subject line should probably read "disable uncached...". > > > > Ugh, of course ... > > > With that fixed the patch is Reviewed-by: Christian König > > . > > Same: Reviewed-by: Alex Deucher > > Thanks. > ___ > amd-gfx mailing list > amd-...@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/amd-gfx ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm: enable uncached DMA optimization for ARM and arm64
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 > Cc: Alex Deucher > Cc: David Zhou > Cc: Huang Rui > Cc: Junwei Zhang > Cc: Michel Daenzer > Cc: David Airlie > Cc: Daniel Vetter > Cc: Maarten Lankhorst > Cc: Maxime Ripard > Cc: Sean Paul > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Will Deacon > Cc: Christoph Hellwig > Cc: Robin Murphy > Cc: amd-gfx list > Cc: dri-devel > Reported-by: Carsten Haitzler > Signed-off-by: Ard Biesheuvel The subject line should probably read "disable uncached...". With that fixed the patch is Reviewed-by: Christian König . Regards, Christian. > --- > include/drm/drm_cache.h | 18 ++ > 1 file changed, 18 insertions(+) > > diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h > index bfe1639df02d..97fc498dc767 100644 > --- a/include/drm/drm_cache.h > +++ b/include/drm/drm_cache.h > @@ -47,6 +47,24 @@ static inline bool drm_arch_can_wc_memory(void) > return false; > #elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3) > return false; > +#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64) > + /* > + * 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. > + */ > + return false; > #else > return true; > #endif ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
