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SubjectRe: [PATCH v2 7/8] drm/msm/a6xx: Support split pagetables
On Fri, Nov 22, 2019 at 3:32 PM Jordan Crouse <jcrouse@codeaurora.org> wrote:
>
> Attempt to enable split pagetables if the arm-smmu driver supports it.
> This will move the default address space from the default region to
> the address range assigned to TTBR1. The behavior should be transparent
> to the driver for now but it gets the default buffers out of the way
> when we want to start swapping TTBR0 for context-specific pagetables.
>
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> ---
>
> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 46 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 5dc0b2c..96b3b28 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -811,6 +811,50 @@ static unsigned long a6xx_gpu_busy(struct msm_gpu *gpu)
> return (unsigned long)busy_time;
> }
>
> +static struct msm_gem_address_space *
> +a6xx_create_address_space(struct msm_gpu *gpu, struct platform_device *pdev)
> +{
> + struct iommu_domain *iommu = iommu_domain_alloc(&platform_bus_type);
> + struct msm_gem_address_space *aspace;
> + struct msm_mmu *mmu;
> + u64 start, size;
> + u32 val = 1;
> + int ret;
> +
> + if (!iommu)
> + return ERR_PTR(-ENOMEM);
> +
> + /* Try to request split pagetables */
> + iommu_domain_set_attr(iommu, DOMAIN_ATTR_SPLIT_TABLES, &val);
> +
> + mmu = msm_iommu_new(&pdev->dev, iommu);
> + if (IS_ERR(mmu)) {
> + iommu_domain_free(iommu);
> + return ERR_CAST(mmu);
> + }
> +
> + /* Check to see if split pagetables were successful */
> + ret = iommu_domain_get_attr(iommu, DOMAIN_ATTR_SPLIT_TABLES, &val);

I assume the split between this and iommu_domain_set_attr() is because
attach needs to happen in between? At any rate, if it needs to be
like this, maybe a comment is in order. As it is it looks like
something future-self would "cleanup"..

BR,
-R

> + if (!ret && val) {
> + /*
> + * The aperture start will be at the beginning of the TTBR1
> + * space so use that as a base
> + */
> + start = iommu->geometry.aperture_start;
> + size = 0xffffffff;
> + } else {
> + /* Otherwise use the legacy 32 bit region */
> + start = SZ_16M;
> + size = 0xffffffff - SZ_16M;
> + }
> +
> + aspace = msm_gem_address_space_create(mmu, "gpu", start, size);
> + if (IS_ERR(aspace))
> + iommu_domain_free(iommu);
> +
> + return aspace;
> +}
> +
> static const struct adreno_gpu_funcs funcs = {
> .base = {
> .get_param = adreno_get_param,
> @@ -832,7 +876,7 @@ static const struct adreno_gpu_funcs funcs = {
> #if defined(CONFIG_DRM_MSM_GPU_STATE)
> .gpu_state_get = a6xx_gpu_state_get,
> .gpu_state_put = a6xx_gpu_state_put,
> - .create_address_space = adreno_iommu_create_address_space,
> + .create_address_space = a6xx_create_address_space,
> #endif
> },
> .get_timestamp = a6xx_get_timestamp,
> --
> 2.7.4
>

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