drm/amdgpu/atif: Send a hotplug event when we get dgpu display request

On PX systems, if the platform supports hotplug events ATIF while the
dGPU is powered down, handle the event and alert userspace.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -25,6 +25,7 @@
 #include <linux/acpi.h>
 #include <linux/slab.h>
 #include <linux/power_supply.h>
+#include <linux/pm_runtime.h>
 #include <acpi/video.h>
 #include <drm/drmP.h>
 #include <drm/drm_crtc_helper.h>
@@ -333,6 +334,16 @@ int amdgpu_atif_handler(struct amdgpu_device *adev,
 #endif
 		}
 	}
+	if (req.pending & ATIF_DGPU_DISPLAY_EVENT) {
+		if ((adev->flags & AMD_IS_PX) &&
+		    amdgpu_atpx_dgpu_req_power_for_displays()) {
+			pm_runtime_get_sync(adev->ddev->dev);
+			/* Just fire off a uevent and let userspace tell us what to do */
+			drm_helper_hpd_irq_event(adev->ddev);
+			pm_runtime_mark_last_busy(adev->ddev->dev);
+			pm_runtime_put_autosuspend(adev->ddev->dev);
+		}
+	}
 	/* TODO: check other events */
 
 	/* We've handled the event, stop the notifier chain. The ACPI interface