s390/pci: create zPCI bus

The zPCI bus is in charge to handle common zPCI resources for
zPCI devices.

Creating the zPCI bus, the PCI bus, the zPCI devices and the
PCI devices and hotplug slots
done in a specific order:
- PCI hotplug slot creation needs a PCI bus
- PCI bus needs a PCI domain
  which is reported by the pci_domain_nr() when setting up the
  host bridge
- PCI domain is set from the zPCI with devfn 0
  this is necessary to have a reproducible enumeration

Therefore we can not create devices or hotplug slots for any PCI
device associated with a zPCI device before having discovered
the function zero of the bus.

The discovery and initialization of devices can be done at several
points in the code:
- On Events, serialized in a thread context
- On initialization, in the kernel init thread context
- When powering on the hotplug slot, in a user thread context

The removal of devices and their parent bus may also be done on
events or for devices when powering down the slot.

To guarantee the existence of the bus and devices until they are
no more needed we use kref in zPCI bus and introduce a reference
count in the zPCI devices.

In this patch the zPCI bus still only accept a device with
a devfn 0.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 147 insertions, 0 deletions

diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
new file mode 100644
index 000000000000..e1565b8537de
--- /dev/null
+++ b/arch/s390/pci/pci_bus.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corp. 2020
+ *
+ * Author(s):
+ *   Pierre Morel <pmorel@linux.ibm.com>
+ *
+ */
+
+#define KMSG_COMPONENT "zpci"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/delay.h>
+#include <linux/seq_file.h>
+#include <linux/jump_label.h>
+#include <linux/pci.h>
+#include <linux/printk.h>
+
+#include <asm/pci_clp.h>
+#include <asm/pci_dma.h>
+
+#include "pci_bus.h"
+
+static LIST_HEAD(zbus_list);
+static DEFINE_SPINLOCK(zbus_list_lock);
+static int zpci_nb_devices;
+
+/* zpci_bus_scan
+ * @zbus: the zbus holding the zdevices
+ * @ops: the pci operations
+ *
+ * The domain number must be set before pci_scan_root_bus is called.
+ * This function can be called once the domain is known, hence
+ * when the function_0 is dicovered.
+ */
+static int zpci_bus_scan(struct zpci_bus *zbus, int domain, struct pci_ops *ops)
+{
+	struct pci_bus *bus;
+	int rc;
+
+	rc = zpci_alloc_domain(domain);
+	if (rc < 0)
+		return rc;
+	zbus->domain_nr = rc;
+
+	bus = pci_scan_root_bus(NULL, ZPCI_BUS_NR, ops, zbus, &zbus->resources);
+	if (!bus) {
+		zpci_free_domain(zbus->domain_nr);
+		return -EFAULT;
+	}
+
+	zbus->bus = bus;
+	pci_bus_add_devices(bus);
+	return 0;
+}
+
+static void zpci_bus_release(struct kref *kref)
+{
+	struct zpci_bus *zbus = container_of(kref, struct zpci_bus, kref);
+
+	pci_lock_rescan_remove();
+	pci_stop_root_bus(zbus->bus);
+
+	zpci_free_domain(zbus->domain_nr);
+	pci_free_resource_list(&zbus->resources);
+
+	pci_remove_root_bus(zbus->bus);
+	pci_unlock_rescan_remove();
+
+	spin_lock(&zbus_list_lock);
+	list_del(&zbus->bus_next);
+	spin_unlock(&zbus_list_lock);
+	kfree(zbus);
+}
+
+static void zpci_bus_put(struct zpci_bus *zbus)
+{
+	kref_put(&zbus->kref, zpci_bus_release);
+}
+
+static struct zpci_bus *zpci_bus_alloc(int pchid)
+{
+	struct zpci_bus *zbus;
+
+	zbus = kzalloc(sizeof(*zbus), GFP_KERNEL);
+	if (!zbus)
+		return NULL;
+
+	zbus->pchid = pchid;
+	INIT_LIST_HEAD(&zbus->bus_next);
+	spin_lock(&zbus_list_lock);
+	list_add_tail(&zbus->bus_next, &zbus_list);
+	spin_unlock(&zbus_list_lock);
+
+	kref_init(&zbus->kref);
+	INIT_LIST_HEAD(&zbus->resources);
+
+	return zbus;
+}
+
+int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
+{
+	struct zpci_bus *zbus;
+	int rc;
+
+	if (zpci_nb_devices == ZPCI_NR_DEVICES) {
+		pr_warn("Adding PCI function %08x failed because the configured limit of %d is reached\n",
+			zdev->fid, ZPCI_NR_DEVICES);
+		return -ENOSPC;
+	}
+	zpci_nb_devices++;
+
+	if (zdev->devfn != ZPCI_DEVFN)
+		return -EINVAL;
+
+	zbus = zpci_bus_alloc(zdev->pchid);
+	if (!zbus)
+		return -ENOMEM;
+
+	zdev->zbus = zbus;
+	zbus->function[ZPCI_DEVFN] = zdev;
+
+	zpci_setup_bus_resources(zdev, &zbus->resources);
+	zbus->max_bus_speed = zdev->max_bus_speed;
+
+	rc = zpci_bus_scan(zbus, (u16)zdev->uid, ops);
+	if (!rc)
+		return 0;
+
+	pr_err("Adding PCI function %08x failed\n", zdev->fid);
+	zdev->zbus = NULL;
+	zpci_bus_put(zbus);
+	return rc;
+}
+
+void zpci_bus_device_unregister(struct zpci_dev *zdev)
+{
+	struct zpci_bus *zbus = zdev->zbus;
+
+	zpci_nb_devices--;
+	zbus->function[ZPCI_DEVFN] = NULL;
+	zpci_bus_put(zbus);
+}