[PATCH 2/9] drm/amdgpu: Add vis_vramlimit module parameter

[john@xxxxxxxxxxxxx (John Brooks)]

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

Signed-off-by: John Brooks <john at fastquake.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h     | 1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 4 ++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 8 ++++++++
 3 files changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c407d2d..fe73633 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -74,6 +74,7 @@
  */
 extern int amdgpu_modeset;
 extern int amdgpu_vram_limit;
+extern int amdgpu_vis_vram_limit;
 extern int amdgpu_gart_size;
 extern int amdgpu_moverate;
 extern int amdgpu_benchmarking;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 4c7c262..a14f458 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -73,6 +73,7 @@
 #define KMS_DRIVER_PATCHLEVEL	0
 
 int amdgpu_vram_limit = 0;
+int amdgpu_vis_vram_limit = 0;
 int amdgpu_gart_size = -1; /* auto */
 int amdgpu_moverate = -1; /* auto */
 int amdgpu_benchmarking = 0;
@@ -119,6 +120,9 @@ 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., -1 = auto)");
 module_param_named(gartsize, amdgpu_gart_size, int, 0600);
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index c9b131b..0676a78 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1095,6 +1095,7 @@ static struct ttm_bo_driver amdgpu_bo_driver = {
 int amdgpu_ttm_init(struct amdgpu_device *adev)
 {
 	int r;
+	u64 vis_vram_limit;
 
 	r = amdgpu_ttm_global_init(adev);
 	if (r) {
@@ -1118,6 +1119,13 @@ 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 = 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);
 
-- 
2.7.4