Re: [PATCH 12/18] iommu/tegra-gart: Add IOMMU_DOMAIN_DMA support
From: Dmitry Osipenko <digetx@gmail.com>
Date: 2020-08-20 20:16:12
Also in:
dri-devel, linux-arm-msm, linux-iommu, linux-media, linux-mediatek, linux-samsung-soc, linux-tegra, lkml
20.08.2020 18:08, Robin Murphy пишет:
quoted hunk ↗ jump to hunk
Now that arch/arm is wired up for default domains and iommu-dma, implement the corresponding driver-side support for DMA domains. Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- drivers/iommu/tegra-gart.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c index fac720273889..e081387080f6 100644 --- a/drivers/iommu/tegra-gart.c +++ b/drivers/iommu/tegra-gart.c@@ -9,6 +9,7 @@ #define dev_fmt(fmt) "gart: " fmt +#include <linux/dma-iommu.h> #include <linux/io.h> #include <linux/iommu.h> #include <linux/moduleparam.h>@@ -145,16 +146,22 @@ static struct iommu_domain *gart_iommu_domain_alloc(unsigned type) { struct iommu_domain *domain;
Hello, Robin! Tegra20 GART isn't a real IOMMU, but a small relocation aperture. We would only want to use it for a temporal mappings (managed by GPU driver) for the time while GPU hardware is busy and working with a sparse DMA buffers, the driver will take care of unmapping the sparse buffers once GPU work is finished [1]. In a case of contiguous DMA buffers, we want to bypass the IOMMU and use buffer's phys address because GART aperture is small and all buffers simply can't fit into GART for a complex GPU operations that involve multiple buffers [2][3]. The upstream GPU driver still doesn't support GART, but eventually it needs to be changed. [1] https://github.com/grate-driver/linux/blob/master/drivers/gpu/drm/tegra/gart.c#L489 [2] https://github.com/grate-driver/linux/blob/master/drivers/gpu/drm/tegra/gart.c#L542 [3] https://github.com/grate-driver/linux/blob/master/drivers/gpu/drm/tegra/uapi/patching.c#L90
- if (type != IOMMU_DOMAIN_UNMANAGED) + if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA) return NULL;
Will a returned NULL tell to IOMMU core that implicit domain shouldn't be used? Is it possible to leave this driver as-is? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel