powerpc/pseries: Add shutdown() to vio_driver and vio_bus

Currently, neither the vio_bus or vio_driver structures provide support
for a shutdown() routine.

Add support for shutdown() by allowing drivers to provide a
implementation via function pointer in their vio_driver struct and
provide a proper implementation in the driver template for the vio_bus
that calls a vio drivers shutdown() if defined.

In the case that no shutdown() is defined by a vio driver and a kexec is
in progress we implement a big hammer that calls remove() to ensure no
further DMA for the devices is possible.
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210402001325.939668-1-tyreld@linux.ibm.com

arch/powerpc/include/asm/vio.h

@@ -114,6 +114,7 @@ struct vio_driver {
 	const struct vio_device_id *id_table;
 	int (*probe)(struct vio_dev *dev, const struct vio_device_id *id);
 	void (*remove)(struct vio_dev *dev);
+	void (*shutdown)(struct vio_dev *dev);
 	/* A driver must have a get_desired_dma() function to
 	 * be loaded in a CMO environment if it uses DMA.
 	 */

arch/powerpc/platforms/pseries/vio.c

@@ -22,6 +22,7 @@
 #include <linux/mm.h>
 #include <linux/dma-map-ops.h>
 #include <linux/kobject.h>
+#include <linux/kexec.h>
 
 #include <asm/iommu.h>
 #include <asm/dma.h>
@@ -1278,6 +1279,20 @@ static int vio_bus_remove(struct device *dev)
 	return 0;
 }
 
+static void vio_bus_shutdown(struct device *dev)
+{
+	struct vio_dev *viodev = to_vio_dev(dev);
+	struct vio_driver *viodrv;
+
+	if (dev->driver) {
+		viodrv = to_vio_driver(dev->driver);
+		if (viodrv->shutdown)
+			viodrv->shutdown(viodev);
+		else if (kexec_in_progress)
+			vio_bus_remove(dev);
+	}
+}
+
 /**
  * vio_register_driver: - Register a new vio driver
  * @viodrv:	The vio_driver structure to be registered.
@@ -1617,6 +1632,7 @@ struct bus_type vio_bus_type = {
 	.match = vio_bus_match,
 	.probe = vio_bus_probe,
 	.remove = vio_bus_remove,
+	.shutdown = vio_bus_shutdown,
 };
 
 /**