drm/amd/powerplay: fix null pointer dereference around dpm state relates

DPM state relates are not supported on the new SW SMU ASICs. But still
it's not OK to trigger null pointer dereference on accessing them.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -159,12 +159,16 @@ static ssize_t amdgpu_get_dpm_state(struct device *dev,
 	struct amdgpu_device *adev = ddev->dev_private;
 	enum amd_pm_state_type pm;
 
-	if (is_support_sw_smu(adev) && adev->smu.ppt_funcs->get_current_power_state)
-		pm = amdgpu_smu_get_current_power_state(adev);
-	else if (adev->powerplay.pp_funcs->get_current_power_state)
+	if (is_support_sw_smu(adev)) {
+		if (adev->smu.ppt_funcs->get_current_power_state)
+			pm = amdgpu_smu_get_current_power_state(adev);
+		else
+			pm = adev->pm.dpm.user_state;
+	} else if (adev->powerplay.pp_funcs->get_current_power_state) {
 		pm = amdgpu_dpm_get_current_power_state(adev);
-	else
+	} else {
 		pm = adev->pm.dpm.user_state;
+	}
 
 	return snprintf(buf, PAGE_SIZE, "%s\n",
 			(pm == POWER_STATE_TYPE_BATTERY) ? "battery" :
@@ -191,7 +195,11 @@ static ssize_t amdgpu_set_dpm_state(struct device *dev,
 		goto fail;
 	}
 
-	if (adev->powerplay.pp_funcs->dispatch_tasks) {
+	if (is_support_sw_smu(adev)) {
+		mutex_lock(&adev->pm.mutex);
+		adev->pm.dpm.user_state = state;
+		mutex_unlock(&adev->pm.mutex);
+	} else if (adev->powerplay.pp_funcs->dispatch_tasks) {
 		amdgpu_dpm_dispatch_task(adev, AMD_PP_TASK_ENABLE_USER_STATE, &state);
 	} else {
 		mutex_lock(&adev->pm.mutex);

drivers/gpu/drm/amd/powerplay/amdgpu_smu.c

@@ -305,7 +305,8 @@ int smu_get_power_num_states(struct smu_context *smu,
 
 	/* not support power state */
 	memset(state_info, 0, sizeof(struct pp_states_info));
-	state_info->nums = 0;
+	state_info->nums = 1;
+	state_info->states[0] = POWER_STATE_TYPE_DEFAULT;
 
 	return 0;
 }