drm/amdgpu: Add vis_vramlimit module parameter

Allow specifying a limit on visible VRAM via a module parameter. This is
helpful for testing performance under visible VRAM pressure.

v2: Add cast to 64-bit (Christian König)

Signed-off-by: John Brooks <john@fastquake.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 019a4b73e5f5..0d6b0617cdf0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -75,6 +75,7 @@
  */
 extern int amdgpu_modeset;
 extern int amdgpu_vram_limit;
+extern int amdgpu_vis_vram_limit;
 extern unsigned amdgpu_gart_size;
 extern int amdgpu_gtt_size;
 extern int amdgpu_moverate;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index ed760f477542..3c83fe6c5db8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -74,6 +74,7 @@
 #define KMS_DRIVER_PATCHLEVEL   0
 
 int amdgpu_vram_limit = 0;
+int amdgpu_vis_vram_limit = 0;
 unsigned amdgpu_gart_size = 256;
 int amdgpu_gtt_size = -1; /* auto */
 int amdgpu_moverate = -1; /* auto */
@@ -121,6 +122,9 @@ int amdgpu_lbpw = -1;
 MODULE_PARM_DESC(vramlimit, "Restrict VRAM for testing, in megabytes");
 module_param_named(vramlimit, amdgpu_vram_limit, int, 0600);
 
+MODULE_PARM_DESC(vis_vramlimit, "Restrict visible VRAM for testing, in megabytes");
+module_param_named(vis_vramlimit, amdgpu_vis_vram_limit, int, 0444);
+
 MODULE_PARM_DESC(gartsize, "Size of PCIE/IGP gart to setup in megabytes (32, 64, etc.)");
 module_param_named(gartsize, amdgpu_gart_size, uint, 0600);
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index b5420b20c2f5..e238084b7142 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1099,6 +1099,7 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 {
         uint64_t gtt_size;
         int r;
+        u64 vis_vram_limit;
 
         r = amdgpu_ttm_global_init(adev);
         if (r) {
@@ -1122,6 +1123,13 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
                 DRM_ERROR("Failed initializing VRAM heap.\n");
                 return r;
         }
+
+        /* Reduce size of CPU-visible VRAM if requested */
+        vis_vram_limit = (u64)amdgpu_vis_vram_limit * 1024 * 1024;
+        if (amdgpu_vis_vram_limit > 0 &&
+            vis_vram_limit <= adev->mc.visible_vram_size)
+                adev->mc.visible_vram_size = vis_vram_limit;
+
         /* Change the size here instead of the init above so only lpfn is affected */
         amdgpu_ttm_set_active_vram_size(adev, adev->mc.visible_vram_size);