drm/amdgpu/cgs: add refresh rate checking to non-DC display code

Clamp the vblank period to 0 if the refresh rate is larger than
120 hz for non-DC.  This allows us to remove the refresh rate
checks from powerplay for mclk switching.
Reviewed-by: Eric Huang <JinhuiEric.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -953,6 +953,11 @@ static int amdgpu_cgs_get_active_displays_info(struct cgs_device *cgs_device,
 								(amdgpu_crtc->v_border * 2);
 					mode_info->vblank_time_us = vblank_lines * line_time_us;
 					mode_info->refresh_rate = drm_mode_vrefresh(&amdgpu_crtc->hw_mode);
+					/* we have issues with mclk switching with refresh rates
+					 * over 120 hz on the non-DC code.
+					 */
+					if (mode_info->refresh_rate > 120)
+						mode_info->vblank_time_us = 0;
 					mode_info = NULL;
 				}
 			}