gpu: nvgpu: Handle allocators with a base of 0

When an allocator is created with a base of 0 the first allocated
block could well be 0. This appears to be an error since gk20a_balloc()
normally returns 0 for error cases.

This patch removes one block from the allocatable resources when base
is set to 0 so that code using gk20a_balloc() does not get tricked
into thinking valid allocations are OOM cases.

Change-Id: I641642d3f790c4c7860d0d1381f4db6f4f72e709
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/1169764
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a_allocator.c b/drivers/gpu/nvgpu/gk20a/gk20a_allocator.c
index fd721709..d3a9202b 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a_allocator.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a_allocator.c
@@ -285,6 +285,15 @@ int __gk20a_allocator_init(struct gk20a_allocator *a,
         a->blk_size = blk_size;
         a->blk_shift = __ffs(blk_size);
 
+        /*
+         * If base is 0 then modfy base to be the size of one block so that we
+         * can return errors by returning addr == 0.
+         */
+        if (a->base == 0) {
+                a->base = a->blk_size;
+                a->length -= a->blk_size;
+        }
+
         /* blk_size must be greater than 0 and a power of 2. */
         if (blk_size == 0)
                 return -EINVAL;