Am 21.01.19 um 11:06 schrieb Ard Biesheuvel: > Currently, the DRM code assumes that PCI devices are always cache > coherent for DMA, and that this can be selectively overridden for > some buffers using non-cached mappings on the CPU side and PCIe > NoSnoop transactions on the bus side. > > Whether the NoSnoop part is implemented correctly is highly platform > specific. Whether it /matters/ if NoSnoop is implemented correctly or > not is architecture specific: on x86, such transactions are coherent > with the CPU whether the NoSnoop attribute is honored or not. On other > architectures, it depends on whether such transactions may allocate in > caches that are non-coherent with the CPU's uncached mappings. > > Bottom line is that we should not rely on this optimization to work > correctly for cache coherent devices in the general case. On the > other hand, disabling this optimization for non-coherent devices > is likely to cause breakage as well, since the driver will assume > cache coherent PCIe if this optimization is turned off. > > So rename drm_arch_can_wc_memory() to drm_device_can_wc_memory(), and > pass the drm_device pointer into it so we can base the return value > on whether the device is cache coherent or not if not running on > X86. > > 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> > Reported-by: Carsten Haitzler <Carsten.Haitzler@xxxxxxx> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Looks sane to me, but I can't fully judge if the check is actually correct or not. So Acked-by: Christian König <christian.koenig@xxxxxxx> > --- > This is a followup to '[RFC PATCH] drm/ttm: force cached mappings for system > RAM on ARM' > > https://lore.kernel.org/linux-arm-kernel/20190110072841.3283-1-ard.biesheuvel@xxxxxxxxxx/ > > Without t > drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +- > drivers/gpu/drm/radeon/radeon_object.c | 2 +- > include/drm/drm_cache.h | 19 +++++++++++-------- > 3 files changed, 13 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c > index 728e15e5d68a..777fa251838f 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c > @@ -480,7 +480,7 @@ static int amdgpu_bo_do_create(struct amdgpu_device *adev, > /* For architectures that don't support WC memory, > * mask out the WC flag from the BO > */ > - if (!drm_arch_can_wc_memory()) > + if (!drm_device_can_wc_memory(adev->ddev)) > bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC; > #endif > > diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c > index 833e909706a9..610889bf6ab5 100644 > --- a/drivers/gpu/drm/radeon/radeon_object.c > +++ b/drivers/gpu/drm/radeon/radeon_object.c > @@ -249,7 +249,7 @@ int radeon_bo_create(struct radeon_device *rdev, > /* For architectures that don't support WC memory, > * mask out the WC flag from the BO > */ > - if (!drm_arch_can_wc_memory()) > + if (!drm_device_can_wc_memory(rdev->ddev)) > bo->flags &= ~RADEON_GEM_GTT_WC; > #endif > > diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h > index bfe1639df02d..ced63b1207a3 100644 > --- a/include/drm/drm_cache.h > +++ b/include/drm/drm_cache.h > @@ -33,6 +33,8 @@ > #ifndef _DRM_CACHE_H_ > #define _DRM_CACHE_H_ > > +#include <drm/drm_device.h> > +#include <linux/dma-noncoherent.h> > #include <linux/scatterlist.h> > > void drm_clflush_pages(struct page *pages[], unsigned long num_pages); > @@ -41,15 +43,16 @@ void drm_clflush_virt_range(void *addr, unsigned long length); > u64 drm_get_max_iomem(void); > > > -static inline bool drm_arch_can_wc_memory(void) > +static inline bool drm_device_can_wc_memory(struct drm_device *ddev) > { > -#if defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE) > - return false; > -#elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3) > - return false; > -#else > - return true; > -#endif > + if (IS_ENABLED(CONFIG_PPC)) > + return IS_ENABLED(CONFIG_NOT_COHERENT_CACHE); > + else if (IS_ENABLED(CONFIG_MIPS)) > + return !IS_ENABLED(CONFIG_CPU_LOONGSON3); > + else if (IS_ENABLED(CONFIG_X86)) > + return true; > + > + return !dev_is_dma_coherent(ddev->dev); > } > > #endif _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
