drm/amdgpu: Enable SDMA context switching for CIK

Enable SDMA context switching on CIK (copied from sdma_v3_0.c).
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -341,6 +341,33 @@ static void cik_sdma_rlc_stop(struct amdgpu_device *adev)
 	/* XXX todo */
 }
 
+/**
+ * cik_ctx_switch_enable - stop the async dma engines context switch
+ *
+ * @adev: amdgpu_device pointer
+ * @enable: enable/disable the DMA MEs context switch.
+ *
+ * Halt or unhalt the async dma engines context switch (VI).
+ */
+static void cik_ctx_switch_enable(struct amdgpu_device *adev, bool enable)
+{
+	u32 f32_cntl;
+	int i;
+
+	for (i = 0; i < adev->sdma.num_instances; i++) {
+		f32_cntl = RREG32(mmSDMA0_CNTL + sdma_offsets[i]);
+		if (enable) {
+			f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
+					AUTO_CTXSW_ENABLE, 1);
+		} else {
+			f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
+					AUTO_CTXSW_ENABLE, 0);
+		}
+
+		WREG32(mmSDMA0_CNTL + sdma_offsets[i], f32_cntl);
+	}
+}
+
 /**
  * cik_sdma_enable - stop the async dma engines
  *
@@ -537,6 +564,8 @@ static int cik_sdma_start(struct amdgpu_device *adev)
 
 	/* halt the engine before programing */
 	cik_sdma_enable(adev, false);
+	/* enable sdma ring preemption */
+	cik_ctx_switch_enable(adev, true);
 
 	/* start the gfx rings and rlc compute queues */
 	r = cik_sdma_gfx_resume(adev);
@@ -984,6 +1013,7 @@ static int cik_sdma_hw_fini(void *handle)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	cik_ctx_switch_enable(adev, false);
 	cik_sdma_enable(adev, false);
 
 	return 0;