drm/amdgpu/si: Call amdgpu_ttm_set_active_vram_size from si_dma_start/stop

Without this, we were only ever using the first 256MB of VRAM.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97593
Tested-by: Konstantin A. Lepikhov <lakostis@altlinux.org>
Tested-by: Arek Ruśniak <arek.rusi@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/si_dma.c

@@ -132,6 +132,8 @@ static void si_dma_stop(struct amdgpu_device *adev)
 		rb_cntl &= ~DMA_RB_ENABLE;
 		WREG32(DMA_RB_CNTL + sdma_offsets[i], rb_cntl);
 
+		if (adev->mman.buffer_funcs_ring == ring)
+			amdgpu_ttm_set_active_vram_size(adev, adev->mc.visible_vram_size);
 		ring->ready = false;
 	}
 }
@@ -192,6 +194,9 @@ static int si_dma_start(struct amdgpu_device *adev)
 			ring->ready = false;
 			return r;
 		}
+
+		if (adev->mman.buffer_funcs_ring == ring)
+			amdgpu_ttm_set_active_vram_size(adev, adev->mc.real_vram_size);
 	}
 
 	return 0;