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>

4 files changed, 87 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/common/linux/dma.c b/drivers/gpu/nvgpu/common/linux/dma.c
index abcf36f1..eb2d0ac4 100644
--- a/drivers/gpu/nvgpu/common/linux/dma.c
+++ b/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);
 
diff --git a/drivers/gpu/nvgpu/common/linux/nvgpu_mem.c b/drivers/gpu/nvgpu/common/linux/nvgpu_mem.c
index b46dbb6b..58488067 100644
--- a/drivers/gpu/nvgpu/common/linux/nvgpu_mem.c
+++ b/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;
+}
diff --git a/drivers/gpu/nvgpu/include/nvgpu/linux/nvgpu_mem.h b/drivers/gpu/nvgpu/include/nvgpu/linux/nvgpu_mem.h
index 8b1e646e..9c52811e 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/linux/nvgpu_mem.h
+++ b/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
diff --git a/drivers/gpu/nvgpu/include/nvgpu/nvgpu_mem.h b/drivers/gpu/nvgpu/include/nvgpu/nvgpu_mem.h
index b01fbec5..66d04ab8 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/nvgpu_mem.h
+++ b/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;
 
         /*