gpu: nvgpu: Remove sg_phys() from GMMU code

Remove the last sg_phys() call from the GMMU code and replace it
with a generic nvgpu_mem API. This new API, nvgpu_mem_get_phys_addr(),
returns the physical address of an nvgpu_mem struct.

Also, implement this new API in the Linux specific nvgpu_mem code
since it requires access to the underlying SGT/SGL.

JIRA NVGPU-68

Change-Id: Idf88701a2a8515464c658c26e0de493c82ff850d
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1542964
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

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

@@ -284,6 +284,14 @@ static u64 nvgpu_mem_get_addr_sysmem(struct gk20a *g, struct nvgpu_mem *mem)
  * Return the base address of %mem. Handles whether this is a VIDMEM or SYSMEM
  * allocation.
  *
+ * Note: this API does not make sense to use for _VIDMEM_ buffers with greater
+ * than one scatterlist chunk. If there's more than one scatterlist chunk then
+ * the buffer will not be contiguous. As such the base address probably isn't
+ * very useful. This is true for SYSMEM as well, if there's no IOMMU.
+ *
+ * However! It _is_ OK to use this on discontiguous sysmem buffers _if_ there's
+ * an IOMMU present and enabled for the GPU.
+ *
  * %attrs can be NULL. If it is not NULL then it may be inspected to determine
  * if the address needs to be modified before writing into a PTE.
  */
@@ -305,6 +313,23 @@ u64 nvgpu_mem_get_addr(struct gk20a *g, struct nvgpu_mem *mem)
 	return alloc->base;
 }
 
+/*
+ * This should only be used on contiguous buffers regardless of whether
+ * there's an IOMMU present/enabled. This applies to both SYSMEM and
+ * VIDMEM.
+ */
+u64 nvgpu_mem_get_phys_addr(struct gk20a *g, struct nvgpu_mem *mem)
+{
+	/*
+	 * For a VIDMEM buf, this is identical to simply get_addr() so just fall
+	 * back to that.
+	 */
+	if (mem->aperture == APERTURE_VIDMEM)
+		return nvgpu_mem_get_addr(g, mem);
+
+	return sg_phys(mem->priv.sgt->sgl);
+}
+
 /*
  * Be careful how you use this! You are responsible for correctly freeing this
  * memory.

drivers/gpu/nvgpu/common/mm/gmmu.c

@@ -212,7 +212,7 @@ u64 nvgpu_pde_phys_addr(struct gk20a *g, struct nvgpu_gmmu_pd *pd)
 	u64 page_addr;
 
 	if (g->mm.has_physical_mode)
-		page_addr = sg_phys(pd->mem->priv.sgt->sgl);
+		page_addr = nvgpu_mem_get_phys_addr(g, pd->mem);
 	else
 		page_addr = nvgpu_mem_get_addr(g, pd->mem);
 

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

@@ -291,6 +291,7 @@ void nvgpu_memset(struct gk20a *g, struct nvgpu_mem *mem, u32 offset,
 		u32 c, u32 size);
 
 u64 nvgpu_mem_get_addr(struct gk20a *g, struct nvgpu_mem *mem);
+u64 nvgpu_mem_get_phys_addr(struct gk20a *g, struct nvgpu_mem *mem);
 
 u32 __nvgpu_aperture_mask(struct gk20a *g, enum nvgpu_aperture aperture,
 		u32 sysmem_mask, u32 vidmem_mask);