[PATCH 2/2] drm/i915: Disable active links before rebooting

[Janusz Krzysztofik]

From: Chris Wilson <chris at chris-wilson.co.uk>

Certain monitors, e.g. Dell, do not like it when we reboot with an
active link, leaving them in a confused state where they refuse to
renegotiate the link after the reboot. If we hook into the reboot
notifier, we can switch off any active link before rebooting, leaving
everything in a consistent, hopefully happy, state.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index af9e0b06bb9c..bab41588f2a9 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -26,6 +26,7 @@
 #include <linux/vgaarb.h>
 #include <linux/vga_switcheroo.h>
 
+#include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
 
 #include "i915_active.h"
@@ -799,6 +800,9 @@ static void i915_pci_shutdown(struct pci_dev *pdev)
 	/* Cancel any outstanding rendering */
 	if (READ_ONCE(i915->gt.awake))
 		i915_gem_set_wedged(i915);
+
+	/* Disable active links to avoid confusing certain (Dell) monitors */
+	drm_atomic_helper_shutdown(&i915->drm);
 }
 
 static struct pci_driver i915_pci_driver = {
-- 
2.21.0