linux-kernel - [PATCH v6 5/5] drm/msm/a6xx: Support split pagetables

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Date:   Thu,  9 Apr 2020 17:33:50 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-arm-msm@...r.kernel.org, robin.murphy@....com,
        will@...nel.org, linux-arm-kernel@...ts.infradead.org,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Sharat Masetty <smasetty@...eaurora.org>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v6 5/5] drm/msm/a6xx: Support split pagetables

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@...eaurora.org>
---

 drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 52 ++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index 02ade43d6335..b27daa77723c 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -825,6 +825,56 @@ 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 - the request has to be made before
+	 * the domian is attached
+	 */
+	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);
+	}
+
+	/*
+	 * After the domain is attached, see if the split tables were actually
+	 * successful.
+	 */
+	ret = iommu_domain_get_attr(iommu, DOMAIN_ATTR_SPLIT_TABLES, &val);
+	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,
@@ -847,7 +897,7 @@ static const struct adreno_gpu_funcs funcs = {
 		.gpu_state_get = a6xx_gpu_state_get,
 		.gpu_state_put = a6xx_gpu_state_put,
 #endif
-		.create_address_space = adreno_iommu_create_address_space,
+		.create_address_space = a6xx_create_address_space,
 	},
 	.get_timestamp = a6xx_get_timestamp,
 };
-- 
2.17.1