[RFC PATCH v1 10/15] drm/msm: Add support for IOMMU auxiliary domains

[Jordan Crouse]

Add support for creating a auxiliary domain from the IOMMU device to
implement per-instance pagetables. Also add a helper function to
return the pagetable base address (ttbr) and asid to the caller so
that the GPU target code can set up the pagetable switch.

Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
---

 drivers/gpu/drm/msm/msm_iommu.c | 97 +++++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/msm/msm_mmu.h   |  4 ++
 2 files changed, 101 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index 1926329..adf9f18 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -21,9 +21,21 @@
 struct msm_iommu {
 	struct msm_mmu base;
 	struct iommu_domain *domain;
+	u64 ttbr;
+	u32 asid;
 };
 #define to_msm_iommu(x) container_of(x, struct msm_iommu, base)
 
+/*
+ * The asid is currently unused for arm-smmu-v2 since all the pagetable
+ * switching does a TLBIALL but still assign a somewhat unique number per
+ * instance to leave open the possibility of being smarter about it
+ *
+ * Accepted range is 32 to 255 (starting at 32 gives a cushion for the asids
+ * assigned to the real context banks in the arm-smmu driver.
+ */
+static int msm_iommu_asid = 32;
+
 static int msm_fault_handler(struct iommu_domain *domain, struct device *dev,
 		unsigned long iova, int flags, void *arg)
 {
@@ -34,6 +46,47 @@ static int msm_fault_handler(struct iommu_domain *domain, struct device *dev,
 	return 0;
 }
 
+static int msm_iommu_aux_attach(struct msm_mmu *mmu, const char * const *names,
+			    int cnt)
+{
+	struct msm_iommu *iommu = to_msm_iommu(mmu);
+	int ret;
+
+	/* Attach the aux device */
+	ret = iommu_aux_attach_device(iommu->domain, mmu->dev);
+	if (ret)
+		return ret;
+
+	/* Get the base address of the pagetable */
+	ret = iommu_domain_get_attr(iommu->domain, DOMAIN_ATTR_PTBASE,
+		&iommu->ttbr);
+	if (ret)
+		return ret;
+
+	/*
+	 * Assign an asid for the instance even though the code doesn't
+	 * currently support per-asid TLB invalidation. There isn't any
+	 * protection on this so two instances could in theory end up with the
+	 * same ASID but that would have very minor performance implications if
+	 * per-ASID TLB invalidation were to be enabled in the future
+	 */
+	iommu->asid = msm_iommu_asid++;
+
+	if (msm_iommu_asid > 0xff)
+		msm_iommu_asid = 32;
+
+	return 0;
+}
+
+static void msm_iommu_aux_detach(struct msm_mmu *mmu, const char * const *names,
+			     int cnt)
+{
+	struct msm_iommu *iommu = to_msm_iommu(mmu);
+
+	iommu->ttbr = 0;
+	iommu->asid = 0;
+}
+
 static int msm_iommu_attach(struct msm_mmu *mmu, const char * const *names,
 			    int cnt)
 {
@@ -86,6 +139,50 @@ static const struct msm_mmu_funcs funcs = {
 		.destroy = msm_iommu_destroy,
 };
 
+static const struct msm_mmu_funcs aux_funcs = {
+		.attach = msm_iommu_aux_attach,
+		.detach = msm_iommu_aux_detach,
+		.map = msm_iommu_map,
+		.unmap = msm_iommu_unmap,
+		.destroy = msm_iommu_destroy,
+};
+
+bool msm_iommu_get_ptinfo(struct msm_mmu *mmu, u64 *ttbr, u32 *asid)
+{
+	struct msm_iommu *iommu = to_msm_iommu(mmu);
+
+	if (!iommu->ttbr)
+		return false;
+
+	if (ttbr)
+		*ttbr = iommu->ttbr;
+	if (asid)
+		*asid = iommu->asid;
+
+	return true;
+}
+
+
+struct msm_mmu *msm_iommu_new_instance(struct device *dev)
+{
+	struct msm_iommu *iommu;
+
+	iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
+	if (!iommu)
+		return ERR_PTR(-ENOMEM);
+
+	/* Create a new domain that will be attached as an aux domain */
+	iommu->domain = iommu_domain_alloc(&platform_bus_type);
+	if (!iommu->domain) {
+		kfree(iommu);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	msm_mmu_init(&iommu->base, dev, &aux_funcs);
+
+	return &iommu->base;
+}
+
 struct msm_mmu *msm_iommu_new(struct device *dev, struct iommu_domain *domain)
 {
 	struct msm_iommu *iommu;
diff --git a/drivers/gpu/drm/msm/msm_mmu.h b/drivers/gpu/drm/msm/msm_mmu.h
index d21b266..f430903 100644
--- a/drivers/gpu/drm/msm/msm_mmu.h
+++ b/drivers/gpu/drm/msm/msm_mmu.h
@@ -46,6 +46,10 @@ static inline void msm_mmu_init(struct msm_mmu *mmu, struct device *dev,
 struct msm_mmu *msm_iommu_new(struct device *dev, struct iommu_domain *domain);
 struct msm_mmu *msm_gpummu_new(struct device *dev, struct msm_gpu *gpu);
 
+struct msm_mmu *msm_iommu_new_instance(struct device *dev);
+
+bool msm_iommu_get_ptinfo(struct msm_mmu *mmu, u64 *ttbr, u32 *asid);
+
 static inline void msm_mmu_set_fault_handler(struct msm_mmu *mmu, void *arg,
 		int (*handler)(void *arg, unsigned long iova, int flags))
 {
-- 
2.7.4