[PATCH 2/5] PCI: add functionality for resizing resources

[Christian KÃnig]

From: Christian KÃnig <christian.koenig@xxxxxxx>

This allows device drivers to request resizing their BARs.

The function only tries to reprogram the windows of the bridge directly above
the requesting device and only the BAR of the same type (usually mem, 64bit,
prefetchable). This is done to make sure not to disturb other drivers by
changing the BARs of their devices.

If reprogramming the bridge BAR fails the old status is restored and -ENOSPC
returned to the calling device driver.

Signed-off-by: Christian KÃnig <christian.koenig@xxxxxxx>
---
 drivers/pci/setup-bus.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/setup-res.c | 45 ++++++++++++++++++++++++++++++++++++
 include/linux/pci.h     |  2 ++
 3 files changed, 108 insertions(+)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index f30ca75..cfab2c7 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1923,6 +1923,67 @@ void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)
 }
 EXPORT_SYMBOL_GPL(pci_assign_unassigned_bridge_resources);
 
+int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
+{
+	const unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
+		IORESOURCE_PREFETCH | IORESOURCE_MEM_64;
+
+	struct resource saved;
+	LIST_HEAD(add_list);
+	LIST_HEAD(fail_head);
+	struct pci_dev_resource *fail_res;
+	unsigned i;
+	int ret = 0;
+
+	/* Release all children from the matching bridge resource */
+	for (i = PCI_BRIDGE_RESOURCES; i < PCI_BRIDGE_RESOURCE_END; ++i) {
+		struct resource *res = &bridge->resource[i];
+
+		if ((res->flags & type_mask) != (type & type_mask))
+			continue;
+
+		saved = *res;
+		if (res->parent) {
+			release_child_resources(res);
+			release_resource(res);
+		}
+		res->start = 0;
+		res->end = 0;
+		break;
+	}
+
+	if (i == PCI_BRIDGE_RESOURCE_END)
+		return -ENOENT;
+
+	__pci_bus_size_bridges(bridge->subordinate, &add_list);
+	__pci_bridge_assign_resources(bridge, &add_list, &fail_head);
+	BUG_ON(!list_empty(&add_list));
+
+	/* restore size and flags */
+	list_for_each_entry(fail_res, &fail_head, list) {
+		struct resource *res = fail_res->res;
+
+		res->start = fail_res->start;
+		res->end = fail_res->end;
+		res->flags = fail_res->flags;
+	}
+
+	/* Revert to the old configuration */
+	if (!list_empty(&fail_head)) {
+		struct resource *res = &bridge->resource[i];
+
+		res->start = saved.start;
+		res->end = saved.end;
+		res->flags = saved.flags;
+
+		pci_claim_resource(bridge, i);
+		ret = -ENOSPC;
+	}
+
+	free_list(&fail_head);
+	return ret;
+}
+
 void pci_assign_unassigned_bus_resources(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index 9526e34..d03e6f1 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -363,6 +363,51 @@ int pci_reassign_resource(struct pci_dev *dev, int resno, resource_size_t addsiz
 	return 0;
 }
 
+int pci_resize_resource(struct pci_dev *dev, int resno, int size)
+{
+	struct resource *res = dev->resource + resno;
+	u32 sizes = pci_rbar_get_sizes(dev, resno);
+	int old = pci_rbar_get_size(dev, resno);
+	u64 bytes = 1ULL << (size + 20);
+	int ret = 0;
+
+	if (!sizes)
+		return -ENOTSUPP;
+
+	if (!(sizes & (1 << size)))
+		return -EINVAL;
+
+	if (old < 0)
+		return old;
+
+	/* Make sure the resource isn't assigned before making it larger. */
+	if (resource_size(res) < bytes && res->parent) {
+		release_resource(res);
+		res->end = resource_size(res) - 1;
+		res->start = 0;
+		if (resno < PCI_BRIDGE_RESOURCES)
+			pci_update_resource(dev, resno);
+	}
+
+	if (pci_rbar_set_size(dev, resno, size))
+		res->end = res->start + bytes - 1;
+	else
+		return -EIO;
+
+	ret = pci_reassign_bridge_resources(dev->bus->self, res->flags);
+	if (ret) {
+		pci_rbar_set_size(dev, resno, old);
+		res->end = res->start + (1ULL << (old + 20)) - 1;
+
+		pci_assign_unassigned_bus_resources(dev->bus);
+		pci_setup_bridge(dev->bus);
+	}
+
+	pci_reenable_device(dev->bus->self);
+	return ret;
+}
+EXPORT_SYMBOL(pci_resize_resource);
+
 int pci_enable_resources(struct pci_dev *dev, int mask)
 {
 	u16 cmd, old_cmd;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9f26ca4..c85d8d7 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1055,6 +1055,7 @@ void pci_reset_bridge_secondary_bus(struct pci_dev *dev);
 void pci_update_resource(struct pci_dev *dev, int resno);
 int __must_check pci_assign_resource(struct pci_dev *dev, int i);
 int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
+int __must_check pci_resize_resource(struct pci_dev *dev, int i, int size);
 int pci_select_bars(struct pci_dev *dev, unsigned long flags);
 bool pci_device_is_present(struct pci_dev *pdev);
 void pci_ignore_hotplug(struct pci_dev *dev);
@@ -1135,6 +1136,7 @@ void pci_assign_unassigned_resources(void);
 void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge);
 void pci_assign_unassigned_bus_resources(struct pci_bus *bus);
 void pci_assign_unassigned_root_bus_resources(struct pci_bus *bus);
+int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type);
 void pdev_enable_device(struct pci_dev *);
 int pci_enable_resources(struct pci_dev *, int mask);
 void pci_fixup_irqs(u8 (*)(struct pci_dev *, u8 *),
-- 
2.7.4