gpu: nvgpu: Update gk20a pde bit coverage function

The mm_gk20a.c function that returns number of bits that a PDE covers
is very useful for determing PDE size for all chips. Copy this into
the common VM code since this applies to all chips/platforms.

Bug 200105199

Change-Id: I437da4781be2fa7c540abe52b20f4c4321f6c649
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1639730
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/common/mm/vm.c b/drivers/gpu/nvgpu/common/mm/vm.c
index e90437a3..19cc9fc5 100644
--- a/drivers/gpu/nvgpu/common/mm/vm.c
+++ b/drivers/gpu/nvgpu/common/mm/vm.c
@@ -60,6 +60,26 @@ int vm_aspace_id(struct vm_gk20a *vm)
         return vm->as_share ? vm->as_share->id : -1;
 }
 
+/*
+ * Determine how many bits of the address space each last level PDE covers. For
+ * example, for gp10b, with a last level address bit PDE range of 28 to 21 the
+ * amount of memory each last level PDE addresses is 21 bits - i.e 2MB.
+ */
+int nvgpu_vm_pde_coverage_bit_count(struct vm_gk20a *vm)
+{
+        int final_pde_level = 0;
+
+        /*
+         * Find the second to last level of the page table programming
+         * heirarchy: the last level is PTEs so we really want the level
+         * before that which is the last level of PDEs.
+         */
+        while (vm->mmu_levels[final_pde_level + 2].update_entry)
+                final_pde_level++;
+
+        return vm->mmu_levels[final_pde_level].lo_bit[0];
+}
+
 static void __nvgpu_vm_free_entries(struct vm_gk20a *vm,
                                     struct nvgpu_gmmu_pd *pd,
                                     int level)