drm/nouveau/pci: do a msi rearm on init

BugLink: http://bugs.launchpad.net/bugs/1764316

[ Upstream commit a121027d ]

On my GP107 when I load nouveau after unloading it, for some reason the
GPU stopped sending or the CPU stopped receiving interrupts if MSI was
enabled.

Doing a rearm once before getting any interrupts fixes this.
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c

@@ -127,6 +127,13 @@ nvkm_pci_init(struct nvkm_subdev *subdev)
 		return ret;
 
 	pci->irq = pdev->irq;
+
+	/* Ensure MSI interrupts are armed, for the case where there are
+	 * already interrupts pending (for whatever reason) at load time.
+	 */
+	if (pci->msi)
+		pci->func->msi_rearm(pci);
+
 	return ret;
 }