[PATCH 2/2] drm/nouveau: Check that the device is enabled before processing interrupt

[Alex Williamson <alex.williamson@redhat.com>]

We're likely to be sharing an interrupt line with other devices,
which means our handler might get called after we've turned off
the device via vga switcheroo.  This can lead to all sorts of
badness, like nv04_fifo_isr() spewing "PFIFO still angry after
100 spins, halt" to the console before the system enters a hard
hang.

We can avoid this by simply checking if the device is still
enabled before processing an interrupt.  To avoid races, flush
any inflight interrupts using synchronize_irq().  Note that
since pci_intx() is called after pci_save_state(),
pci_restore_state() will automatically re-enable INTx.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 drivers/gpu/drm/nouveau/nouveau_drv.c |    2 ++
 drivers/gpu/drm/nouveau/nouveau_irq.c |    3 +++
 2 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.c b/drivers/gpu/drm/nouveau/nouveau_drv.c
index 155ebdc..405d4f1 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drv.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drv.c
@@ -230,7 +230,9 @@ nouveau_pci_suspend(struct pci_dev *pdev, pm_message_t pm_state)
 	NV_INFO(dev, "And we're gone!\n");
 	pci_save_state(pdev);
 	if (pm_state.event == PM_EVENT_SUSPEND) {
+		pci_intx(pdev, 0);
 		pci_disable_device(pdev);
+		synchronize_irq(drm_dev_to_irq(dev));
 		pci_set_power_state(pdev, PCI_D3hot);
 	}
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_irq.c b/drivers/gpu/drm/nouveau/nouveau_irq.c
index 2ba7265..8fd17e6 100644
--- a/drivers/gpu/drm/nouveau/nouveau_irq.c
+++ b/drivers/gpu/drm/nouveau/nouveau_irq.c
@@ -78,6 +78,9 @@ nouveau_irq_handler(DRM_IRQ_ARGS)
 	u32 stat;
 	int i;
 
+	if (unlikely(!pci_is_enabled(dev->pdev)))
+		return IRQ_NONE;
+
 	stat = nv_rd32(dev, NV03_PMC_INTR_0);
 	if (!stat)
 		return IRQ_NONE;