[6/6] instmem/gk20a: add IOMMU support

diff --git a/drm/nouveau/nvkm/subdev/instmem/gk20a.c b/drm/nouveau/nvkm/subdev/instmem/gk20a.c
index 4c8af6e..f7c305a 100644
--- a/drm/nouveau/nvkm/subdev/instmem/gk20a.c
+++ b/drm/nouveau/nvkm/subdev/instmem/gk20a.c
@@ -20,12 +20,32 @@ 
  * DEALINGS IN THE SOFTWARE.
  */
 
+/*
+ * GK20A does not have dedicated video memory, and to accurately represent this
+ * fact Nouveau will not create a RAM device for it. Therefore its instmem
+ * implementation must be done directly on top of system memory, while providing
+ * coherent read and write operations.
+ *
+ * Instmem can be allocated through two means:
+ * 1) If a IOMMU mapping has been probed, the IOMMU API is used to make memory
+ *    pages contiguous to the GPU. This is the preferred way.
+ * 2) If no IOMMU mapping is probed, the DMA API is used to allocated physically
+ *    contiguous memory.
+ *
+ * In both cases CPU read and writes are performed using PRAMIN (i.e. using the
+ * GPU path) to ensure these operations are coherent for the GPU. This allows us
+ * to use more "relaxed" allocation parameters when using the DMA API, since we
+ * never need a kernel mapping.
+ */
+
 #include <subdev/fb.h>
 #include <core/mm.h>
 #include <core/device.h>
 
 #ifdef __KERNEL__
 #include <linux/dma-attrs.h>
+#include <linux/iommu.h>
+#include <nouveau_platform.h>
 #endif
 
 #include "priv.h"
@@ -36,18 +56,51 @@  struct gk20a_instobj_priv {
 	struct nvkm_mem *mem;
 	/* Pointed by mem */
 	struct nvkm_mem _mem;
+};
+
+/*
+ * Used for objects allocated using the DMA API
+ */
+struct gk20a_instobj_dma {
+	struct gk20a_instobj_priv base;
+
 	void *cpuaddr;
 	dma_addr_t handle;
 	struct dma_attrs attrs;
 	struct nvkm_mm_node r;
 };
 
+/*
+ * Used for objects flattened using the IOMMU API
+ */
+struct gk20a_instobj_iommu {
+	struct gk20a_instobj_priv base;
+
+	/* array of base.mem->size pages */
+	struct page *pages[];
+};
+
 struct gk20a_instmem_priv {
 	struct nvkm_instmem base;
 	spinlock_t lock;
 	u64 addr;
+
+	/* Only used if IOMMU if present */
+	struct mutex *mm_mutex;
+	struct nvkm_mm *mm;
+	struct iommu_domain *domain;
+	unsigned long iommu_pgshift;
 };
 
+/*
+ * Use PRAMIN to read/write data and avoid coherency issues.
+ * PRAMIN uses the GPU path and ensures data will always be coherent.
+ *
+ * A dynamic mapping based solution would be desirable in the future, but
+ * the issue remains of how to maintain coherency efficiently. On ARM it is
+ * not easy (if possible at all?) to create uncached temporary mappings.
+ */
+
 static u32
 gk20a_instobj_rd32(struct nvkm_object *object, u64 offset)
 {
@@ -87,50 +140,79 @@  gk20a_instobj_wr32(struct nvkm_object *object, u64 offset, u32 data)
 }
 
 static void
-gk20a_instobj_dtor(struct nvkm_object *object)
+gk20a_instobj_dtor_dma(struct gk20a_instobj_priv *_node)
 {
-	struct gk20a_instobj_priv *node = (void *)object;
+	struct gk20a_instobj_dma *node = (void *)_node;
 	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(node);
 	struct device *dev = nv_device_base(nv_device(priv));
 
 	if (unlikely(!node->handle))
 		return;
 
-	dma_free_attrs(dev, node->mem->size << PAGE_SHIFT, node->cpuaddr,
+	dma_free_attrs(dev, _node->mem->size << PAGE_SHIFT, node->cpuaddr,
 		       node->handle, &node->attrs);
+}
+
+static void
+gk20a_instobj_dtor_iommu(struct gk20a_instobj_priv *_node)
+{
+	struct gk20a_instobj_iommu *node = (void *)_node;
+	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(node);
+	struct nvkm_mm_node *r;
+	int i;
+
+	if (unlikely(list_empty(&_node->mem->regions)))
+		return;
+
+	r = list_first_entry(&_node->mem->regions, struct nvkm_mm_node,
+			     rl_entry);
+
+	/* clear bit 34 to unmap pages */
+	r->offset &= ~BIT(34 - priv->iommu_pgshift);
+
+	/* Unmap pages from GPU address space and free them */
+	for (i = 0; i < _node->mem->size; i++) {
+		iommu_unmap(priv->domain,
+			    (r->offset + i) << priv->iommu_pgshift, PAGE_SIZE);
+		__free_page(node->pages[i]);
+	}
+
+	/* Release area from GPU address space */
+	mutex_lock(priv->mm_mutex);
+	nvkm_mm_free(priv->mm, &r);
+	mutex_unlock(priv->mm_mutex);
+}
+
+static void
+gk20a_instobj_dtor(struct nvkm_object *object)
+{
+	struct gk20a_instobj_priv *node = (void *)object;
+	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(node);
+
+	if (priv->domain)
+		gk20a_instobj_dtor_iommu(node);
+	else
+		gk20a_instobj_dtor_dma(node);
 
 	nvkm_instobj_destroy(&node->base);
 }
 
 static int
-gk20a_instobj_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
-		   struct nvkm_oclass *oclass, void *data, u32 _size,
-		   struct nvkm_object **pobject)
+gk20a_instobj_ctor_dma(struct nvkm_object *parent, struct nvkm_object *engine,
+		       struct nvkm_oclass *oclass, u32 npages, u32 align,
+		       struct gk20a_instobj_priv **_node)
 {
-	struct nvkm_instobj_args *args = data;
+	struct gk20a_instobj_dma *node;
 	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(parent);
-	struct device *dev = nv_device_base(nv_device(priv));
-	struct gk20a_instobj_priv *node;
-	u32 size, align;
-	u32 npages;
+	struct device *dev = nv_device_base(nv_device(parent));
 	int ret;
 
-	nv_debug(parent, "%s: size: %x align: %x\n", __func__,
-		 args->size, args->align);
-
-	size  = max((args->size  + 4095) & ~4095, (u32)4096);
-	align = max((args->align + 4095) & ~4095, (u32)4096);
-
-	npages = size >> PAGE_SHIFT;
-
 	ret = nvkm_instobj_create_(parent, engine, oclass, sizeof(*node),
-				      (void **)&node);
-	*pobject = nv_object(node);
+				   (void **)&node);
+	*_node = &node->base;
 	if (ret)
 		return ret;
 
-	node->mem = &node->_mem;
-
 	init_dma_attrs(&node->attrs);
 	/*
 	 * We will access this memory through PRAMIN and thus do not need a
@@ -154,16 +236,132 @@  gk20a_instobj_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
 		nv_warn(priv, "memory not aligned as requested: %pad (0x%x)\n",
 			&node->handle, align);
 
-	node->mem->offset = node->handle;
+	/* present memory for being mapped using small pages */
+	node->r.type = 12;
+	node->r.offset = node->handle >> 12;
+	node->r.length = (npages << PAGE_SHIFT) >> 12;
+
+	node->base._mem.offset = node->handle;
+
+	INIT_LIST_HEAD(&node->base._mem.regions);
+	list_add_tail(&node->r.rl_entry, &node->base._mem.regions);
+
+	return 0;
+}
+
+static int
+gk20a_instobj_ctor_iommu(struct nvkm_object *parent, struct nvkm_object *engine,
+			 struct nvkm_oclass *oclass, u32 npages, u32 align,
+			 struct gk20a_instobj_priv **_node)
+{
+	struct gk20a_instobj_iommu *node;
+	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(parent);
+	struct nvkm_mm_node *r;
+	int ret;
+	int i;
+
+	ret = nvkm_instobj_create_(parent, engine, oclass,
+				sizeof(*node) + sizeof(node->pages[0]) * npages,
+				(void **)&node);
+	*_node = &node->base;
+	if (ret)
+		return ret;
+
+	/* Allocate backing memory */
+	for (i = 0; i < npages; i++) {
+		struct page *p = alloc_page(GFP_KERNEL);
+
+		if (p == NULL) {
+			ret = -ENOMEM;
+			goto free_pages;
+		}
+		node->pages[i] = p;
+	}
+
+	mutex_lock(priv->mm_mutex);
+	/* Reserve area from GPU address space */
+	ret = nvkm_mm_head(priv->mm, 0, 1, npages, npages,
+			   align >> priv->iommu_pgshift, &r);
+	mutex_unlock(priv->mm_mutex);
+	if (ret) {
+		nv_error(priv, "virtual space is full!\n");
+		goto free_pages;
+	}
+
+	/* Map into GPU address space */
+	for (i = 0; i < npages; i++) {
+		struct page *p = node->pages[i];
+		u32 offset = (r->offset + i) << priv->iommu_pgshift;
+
+		ret = iommu_map(priv->domain, offset, page_to_phys(p),
+				PAGE_SIZE, IOMMU_READ | IOMMU_WRITE);
+		if (ret < 0) {
+			nv_error(priv, "IOMMU mapping failure: %d\n", ret);
+
+			while (i-- > 0) {
+				offset -= PAGE_SIZE;
+				iommu_unmap(priv->domain, offset, PAGE_SIZE);
+			}
+			goto release_area;
+		}
+	}
+
+	/* Bit 34 tells that an address is to be resolved through the IOMMU */
+	r->offset |= BIT(34 - priv->iommu_pgshift);
+
+	node->base._mem.offset = ((u64)r->offset) << priv->iommu_pgshift;
+
+	INIT_LIST_HEAD(&node->base._mem.regions);
+	list_add_tail(&r->rl_entry, &node->base._mem.regions);
+
+	return 0;
+
+release_area:
+	mutex_lock(priv->mm_mutex);
+	nvkm_mm_free(priv->mm, &r);
+	mutex_unlock(priv->mm_mutex);
+
+free_pages:
+	for (i = 0; i < npages && node->pages[i] != NULL; i++)
+		__free_page(node->pages[i]);
+
+	return ret;
+}
+
+static int
+gk20a_instobj_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
+		   struct nvkm_oclass *oclass, void *data, u32 _size,
+		   struct nvkm_object **pobject)
+{
+	struct nvkm_instobj_args *args = data;
+	struct gk20a_instmem_priv *priv = (void *)nvkm_instmem(parent);
+	struct gk20a_instobj_priv *node;
+	u32 size, align;
+	int ret;
+
+	nv_debug(parent, "%s (%s): size: %x align: %x\n", __func__,
+		 priv->domain ? "DMA" : "IOMMU", args->size, args->align);
+
+	/* Round size and align to page bounds */
+	size = max((args->size  + ~PAGE_MASK) & PAGE_MASK, (u32)PAGE_SIZE);
+	align = max((args->align + ~PAGE_MASK) & PAGE_MASK, (u32)PAGE_SIZE);
+
+	if (priv->domain)
+		ret = gk20a_instobj_ctor_iommu(parent, engine, oclass,
+					      size >> PAGE_SHIFT, align, &node);
+	else
+		ret = gk20a_instobj_ctor_dma(parent, engine, oclass,
+					     size >> PAGE_SHIFT, align, &node);
+	*pobject = nv_object(node);
+	if (ret)
+		return ret;
+
+	node->mem = &node->_mem;
+
+	/* present memory for being mapped using small pages */
 	node->mem->size = size >> 12;
 	node->mem->memtype = 0;
 	node->mem->page_shift = 12;
-	INIT_LIST_HEAD(&node->mem->regions);
-
-	node->r.type = 12;
-	node->r.offset = node->handle >> 12;
-	node->r.length = npages;
-	list_add_tail(&node->r.rl_entry, &node->mem->regions);
 
 	node->base.addr = node->mem->offset;
 	node->base.size = size;
@@ -202,6 +400,7 @@  gk20a_instmem_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
 		   struct nvkm_object **pobject)
 {
 	struct gk20a_instmem_priv *priv;
+	struct nouveau_platform_device *plat;
 	int ret;
 
 	ret = nvkm_instmem_create(parent, engine, oclass, &priv);
@@ -211,6 +410,18 @@  gk20a_instmem_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
 
 	spin_lock_init(&priv->lock);
 
+	plat = nv_device_to_platform(nv_device(parent));
+	if (plat->gpu->iommu.domain) {
+		priv->domain = plat->gpu->iommu.domain;
+		priv->mm = plat->gpu->iommu.mm;
+		priv->iommu_pgshift = plat->gpu->iommu.pgshift;
+		priv->mm_mutex = &plat->gpu->iommu.mutex;
+
+		nv_info(priv, "using IOMMU\n");
+	} else {
+		nv_info(priv, "using DMA API\n");
+	}
+
 	return 0;
 }
 
@@ -225,4 +436,3 @@  gk20a_instmem_oclass = &(struct nvkm_instmem_impl) {
 	},
 	.instobj = &gk20a_instobj_oclass.base,
 }.base;
-