drm/i915: Shut down displays gracefully on reboot

Implement the pci .shutdown() hook in order to quiesce the
hardware prior to reboot. The main purpose here is to turn
all displays off. Some displays/other drivers tend to get
confused if the state after reboot isn't exactly as they
expected.

One specific example was the Dell UP2414Q in MST mode.
It would require me to pull the power cord after a reboot
or else it would just not come back to life. Sadly I don't
have that at hand anymore so not sure if it's still
misbehaving without the graceful shutdown, or if we
managed to fix something else since I last tested it.

For good measure we do a gem suspend as well, so that
we match the suspend flow more closely. Also stopping
all DMA and whatnot is probably a good idea for kexec.
I would expect that some kind of GT reset happens on
normal reboot so probably not totally necessary there.

v2: Use the pci .shutdown() hook instead of a reboot notifier (Lukas)
    Do the gem suspend for kexec (Chris)

Cc: Lukas Wunner <lukas@wunner.de>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201001151640.14590-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.c

@@ -1037,6 +1037,22 @@ static void intel_suspend_encoders(struct drm_i915_private *dev_priv)
 	drm_modeset_unlock_all(dev);
 }
 
+void i915_driver_shutdown(struct drm_i915_private *i915)
+{
+	i915_gem_suspend(i915);
+
+	drm_kms_helper_poll_disable(&i915->drm);
+
+	drm_atomic_helper_shutdown(&i915->drm);
+
+	intel_dp_mst_suspend(i915);
+
+	intel_runtime_pm_disable_interrupts(i915);
+	intel_hpd_cancel_work(i915);
+
+	intel_suspend_encoders(i915);
+}
+
 static bool suspend_to_idle(struct drm_i915_private *dev_priv)
 {
 #if IS_ENABLED(CONFIG_ACPI_SLEEP)

drivers/gpu/drm/i915/i915_drv.h

@@ -1779,6 +1779,7 @@ extern const struct dev_pm_ops i915_pm_ops;
 
 int i915_driver_probe(struct pci_dev *pdev, const struct pci_device_id *ent);
 void i915_driver_remove(struct drm_i915_private *i915);
+void i915_driver_shutdown(struct drm_i915_private *i915);
 
 int i915_resume_switcheroo(struct drm_i915_private *i915);
 int i915_suspend_switcheroo(struct drm_i915_private *i915, pm_message_t state);

drivers/gpu/drm/i915/i915_pci.c

@@ -1090,11 +1090,19 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	return 0;
 }
 
+static void i915_pci_shutdown(struct pci_dev *pdev)
+{
+	struct drm_i915_private *i915 = pci_get_drvdata(pdev);
+
+	i915_driver_shutdown(i915);
+}
+
 static struct pci_driver i915_pci_driver = {
 	.name = DRIVER_NAME,
 	.id_table = pciidlist,
 	.probe = i915_pci_probe,
 	.remove = i915_pci_remove,
+	.shutdown = i915_pci_shutdown,
 	.driver.pm = &i915_pm_ops,
 };