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Ard Biesheuvel ccf970be98 drm: disable uncached DMA optimization for ARM and arm64 
[ Upstream commit e02f5c1bb2 ]

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@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: David Zhou <David1.Zhou@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Junwei Zhang <Jerry.Zhang@amd.com>
Cc: Michel Daenzer <michel.daenzer@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: amd-gfx list <amd-gfx@lists.freedesktop.org>
Cc: dri-devel <dri-devel@lists.freedesktop.org>
Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.kernel.org/patch/10778815/
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-03-13 14:04:19 -07:00
..
acpi pci-v4.20-changes 2018-10-25 06:50:48 -07:00
asm-generic Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-21 09:22:24 -08:00
clocksource
crypto KEYS: asym_tpm: extract key size & public key [ver #2] 2018-10-26 09:30:46 +01:00
drm drm: disable uncached DMA optimization for ARM and arm64 2019-03-13 14:04:19 -07:00
dt-bindings This time it looks like a quieter release cycle in the clk tree. I guess that's 2018-10-31 11:08:30 -07:00
keys KEYS: user: Align the payload buffer 2019-02-27 10:09:54 +01:00
kvm
linux bpf: run bpf programs with preemption disabled 2019-03-13 14:04:13 -07:00
math-emu
media media: cec: keep track of outstanding transmits 2019-01-09 17:46:01 +01:00
memory
misc
net netfilter: nf_tables: unbind set in rule from commit path 2019-03-13 14:04:17 -07:00
pcmcia
ras
rdma RDMA/core: Sync unregistration with netlink commands 2019-02-12 20:02:10 +01:00
scsi
soc ARM: SoC driver updates for 4.17 2018-10-29 15:16:01 -07:00
sound ASoC: soc-core: fix init platform memory handling 2019-02-27 10:09:56 +01:00
target scsi: target/core: Make sure that target_wait_for_sess_cmds() waits long enough 2019-01-26 09:20:45 +01:00
trace afs: Fix race in async call refcounting 2019-02-27 10:09:50 +01:00
uapi binder: create node flag to request sender's security context 2019-03-10 07:10:09 +01:00
video udlfb: handle unplug properly 2018-10-08 12:57:34 +02:00
xen Revert "xen/balloon: Mark unallocated host memory as UNUSABLE" 2018-11-29 17:53:31 +01:00