gpu: nvgpu: Add __nvgpu_mem_create_from_pages()

Add a function to create a nvgpu_mem from a list of arbitrary pages.
This API is useful for pages not necessarily allocated by the Linux
page allocator. It is useful for making nvgpu_mems that represent
carveouts or other things like that.

JIRA NVGPU-12
JIRA NVGPU-30

Change-Id: Ibcb6432f077a6b0ecf9d183248e47a1f9ecb3ddd
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/1464080
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>

drivers/gpu/nvgpu/common/linux/dma.c

@@ -335,6 +335,7 @@ static void nvgpu_dma_free_sys(struct gk20a *g, struct nvgpu_mem *mem)
 	struct device *d = dev_from_gk20a(g);
 
 	if (!(mem->mem_flags & NVGPU_MEM_FLAG_SHADOW_COPY) &&
+	    !(mem->mem_flags & __NVGPU_MEM_FLAG_NO_DMA) &&
 	    (mem->cpu_va || mem->priv.pages)) {
 		if (mem->priv.flags) {
 			DEFINE_DMA_ATTRS(dma_attrs);
@@ -358,6 +359,13 @@ static void nvgpu_dma_free_sys(struct gk20a *g, struct nvgpu_mem *mem)
 		mem->priv.pages = NULL;
 	}
 
+	/*
+	 * When this flag is set we expect that pages is still populated but not
+	 * by the DMA API.
+	 */
+	if (mem->mem_flags & __NVGPU_MEM_FLAG_NO_DMA)
+		nvgpu_kfree(g, mem->priv.pages);
+
 	if (mem->priv.sgt)
 		nvgpu_free_sgtable(g, &mem->priv.sgt);
 

drivers/gpu/nvgpu/common/linux/nvgpu_mem.c

@@ -297,3 +297,41 @@ int nvgpu_mem_create_from_mem(struct gk20a *g,
 
 	return ret;
 }
+
+int __nvgpu_mem_create_from_pages(struct gk20a *g, struct nvgpu_mem *dest,
+				  struct page **pages, int nr_pages)
+{
+	struct sg_table *sgt;
+	struct page **our_pages =
+		nvgpu_kmalloc(g, sizeof(struct page *) * nr_pages);
+
+	if (!our_pages)
+		return -ENOMEM;
+
+	memcpy(our_pages, pages, sizeof(struct page *) * nr_pages);
+
+	if (nvgpu_get_sgtable_from_pages(g, &sgt, pages, 0,
+					 nr_pages * PAGE_SIZE)) {
+		nvgpu_kfree(g, our_pages);
+		return -ENOMEM;
+	}
+
+	/*
+	 * If we are making an SGT from physical pages we can be reasonably
+	 * certain that this should bypass the SMMU - thus we set the DMA (aka
+	 * IOVA) address to 0. This tells the GMMU mapping code to not make a
+	 * mapping directed to the SMMU.
+	 */
+	sg_dma_address(sgt->sgl) = 0;
+
+	dest->mem_flags  = __NVGPU_MEM_FLAG_NO_DMA;
+	dest->aperture   = APERTURE_SYSMEM;
+	dest->skip_wmb   = 0;
+	dest->size       = PAGE_SIZE * nr_pages;
+
+	dest->priv.flags = 0;
+	dest->priv.pages = our_pages;
+	dest->priv.sgt   = sgt;
+
+	return 0;
+}

drivers/gpu/nvgpu/include/nvgpu/linux/nvgpu_mem.h

@@ -20,10 +20,41 @@
 struct page;
 struct sg_table;
 
+struct gk20a;
+struct nvgpu_mem;
+
 struct nvgpu_mem_priv {
 	struct page **pages;
 	struct sg_table *sgt;
 	unsigned long flags;
 };
 
+/**
+ * __nvgpu_mem_create_from_pages - Create an nvgpu_mem from physical pages.
+ *
+ * @g        - The GPU.
+ * @dest     - nvgpu_mem to initialize.
+ * @pages    - A list of page pointers.
+ * @nr_pages - The number of pages in @pages.
+ *
+ * Create a new nvgpu_mem struct from a pre-existing list of physical pages. The
+ * pages need not be contiguous (the underlying scatter gather list will help
+ * with that). However, note, this API will explicitly make it so that the GMMU
+ * mapping code bypasses SMMU access for the passed pages. This allows one to
+ * make mem_descs that describe MMIO regions or other non-DRAM things.
+ *
+ * This only works for SYSMEM (or other things like SYSMEM - basically just not
+ * VIDMEM). Also, this API is only available for Linux as it heavily depends on
+ * the notion of struct %page.
+ *
+ * The resulting nvgpu_mem should be released with the nvgpu_dma_free() or the
+ * nvgpu_dma_unmap_free() function depending on whether or not the resulting
+ * nvgpu_mem has been mapped. The underlying pages themselves must be cleaned up
+ * by the caller of this API.
+ *
+ * Returns 0 on success, or a relevant error otherwise.
+ */
+int __nvgpu_mem_create_from_pages(struct gk20a *g, struct nvgpu_mem *dest,
+				  struct page **pages, int nr_pages);
+
 #endif

drivers/gpu/nvgpu/include/nvgpu/nvgpu_mem.h

@@ -68,6 +68,16 @@ struct nvgpu_mem {
 	 * therefor zeroed (to prevent leaking information in VIDMEM buffers).
 	 */
 #define NVGPU_MEM_FLAG_USER_MEM			 (1 << 2)
+
+	/*
+	 * Internal flag that specifies this struct has not been made with DMA
+	 * memory and as a result should not try to use the DMA routines for
+	 * freeing the backing memory.
+	 *
+	 * However, this will not stop the DMA API from freeing other parts of
+	 * nvgpu_mem in a system specific way.
+	 */
+#define __NVGPU_MEM_FLAG_NO_DMA			 (1 << 3)
 	unsigned long				 mem_flags;
 
 	/*