From: Alex Deucher <alexander.deucher@amd.com>
Date: Thu, 29 Jun 2017 16:08:49 -0400
Subject: drm/amdgpu: fix vblank_time when displays are off
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Git-commit: beb3777682d5c296cc15a2a424f5a7a98476def0
Patch-mainline: v4.13-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

If the displays are off, set the vblank time to max to make
sure mclk switching is enabled.  Avoid mclk getting set
to high when no displays are attached.

bug: https://bugs.freedesktop.org/show_bug.cgi?id=101528
fixes: 09be4a5219 (drm/amd/powerplay/smu7: add vblank check for mclk switching (v2))
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cgs.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cgs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cgs.c
@@ -839,6 +839,8 @@ static int amdgpu_cgs_get_active_display
 
 	mode_info = info->mode_info;
 	if (mode_info) {
+		/* if the displays are off, vblank time is max */
+		mode_info->vblank_time_us = 0xffffffff;
 		/* always set the reference clock */
 		mode_info->ref_clock = adev->clock.spll.reference_freq;
 	}