drm/amd/powerplay: fix segment fault issue in multi-display case.

BugLink: http://bugs.launchpad.net/bugs/1580526

commit f9e9c08e upstream.
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

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

@@ -816,10 +816,13 @@ static int amdgpu_cgs_get_active_displays_info(void *cgs_device,
 	struct drm_device *ddev = adev->ddev;
 	struct drm_crtc *crtc;
 	uint32_t line_time_us, vblank_lines;
+	struct cgs_mode_info *mode_info;
 
 	if (info == NULL)
 		return -EINVAL;
 
+	mode_info = info->mode_info;
+
 	if (adev->mode_info.num_crtc && adev->mode_info.mode_config_initialized) {
 		list_for_each_entry(crtc,
 				&ddev->mode_config.crtc_list, head) {
@@ -828,7 +831,7 @@ static int amdgpu_cgs_get_active_displays_info(void *cgs_device,
 				info->active_display_mask |= (1 << amdgpu_crtc->crtc_id);
 				info->display_count++;
 			}
-			if (info->mode_info != NULL &&
+			if (mode_info != NULL &&
 				crtc->enabled && amdgpu_crtc->enabled &&
 				amdgpu_crtc->hw_mode.clock) {
 				line_time_us = (amdgpu_crtc->hw_mode.crtc_htotal * 1000) /
@@ -836,10 +839,10 @@ static int amdgpu_cgs_get_active_displays_info(void *cgs_device,
 				vblank_lines = amdgpu_crtc->hw_mode.crtc_vblank_end -
 							amdgpu_crtc->hw_mode.crtc_vdisplay +
 							(amdgpu_crtc->v_border * 2);
-				info->mode_info->vblank_time_us = vblank_lines * line_time_us;
-				info->mode_info->refresh_rate = drm_mode_vrefresh(&amdgpu_crtc->hw_mode);
-				info->mode_info->ref_clock = adev->clock.spll.reference_freq;
-				info->mode_info++;
+				mode_info->vblank_time_us = vblank_lines * line_time_us;
+				mode_info->refresh_rate = drm_mode_vrefresh(&amdgpu_crtc->hw_mode);
+				mode_info->ref_clock = adev->clock.spll.reference_freq;
+				mode_info = NULL;
 			}
 		}
 	}