[PATCH v8 06/24] PCI: hotplug: Recalculate every bridge window during rescan

From: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
To: <linux-pci@vger.kernel.org>
Cc: "Bjorn Helgaas" <helgaas@kernel.org>,
	"Lukas Wunner" <lukas@wunner.de>, "Stefan Roese" <sr@denx.de>,
	"Andy Lavr" <andy.lavr@gmail.com>,
	"Christian König" <christian.koenig@amd.com>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"David Laight" <David.Laight@ACULAB.COM>,
	"Rajat Jain" <rajatja@google.com>,
	linux@yadro.com,
	"Sergei Miroshnichenko" <s.miroshnichenko@yadro.com>
Subject: [PATCH v8 06/24] PCI: hotplug: Recalculate every bridge window during rescan
Date: Mon, 27 Apr 2020 21:23:40 +0300	[thread overview]
Message-ID: <20200427182358.2067702-7-s.miroshnichenko@yadro.com> (raw)
In-Reply-To: <20200427182358.2067702-1-s.miroshnichenko@yadro.com>

When the movable BARs feature is enabled and a rescan has been requested,
release all bridge windows and recalculate them from scratch, taking into
account all kinds of BARs: fixed, movable, new.

Comparing to simply trying to expand bridge windows, this also employs the
PCI ability to shuffle BARs within a bridge, increasing the chances to find
a memory space to fit BARs of newly hot-added devices, especially if no (or
not enough) gaps were reserved by the BIOS/bootloader/firmware.

The last step of writing the recalculated windows to the bridges is done by
the new pci_setup_bridges() function.

Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
---
 drivers/pci/pci.h       |  1 +
 drivers/pci/probe.c     | 22 ++++++++++++++++++++++
 drivers/pci/setup-bus.c |  9 +++++++++
 3 files changed, 32 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 25e49c5b998b..c7d3c022bf35 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -286,6 +286,7 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
 				struct list_head *realloc_head,
 				struct list_head *fail_head);
 bool pci_bus_clip_resource(struct pci_dev *dev, int idx);
+void pci_bus_release_root_bridge_resources(struct pci_bus *bus);
 
 void pci_reassigndev_resource_alignment(struct pci_dev *dev);
 void pci_disable_bridge_window(struct pci_dev *dev);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 1ac08b64ce83..5baad5325b16 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -3250,6 +3250,25 @@ static void pci_bus_rescan_done(struct pci_bus *bus)
 	}
 }
 
+static void pci_setup_bridges(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		struct pci_bus *child;
+
+		if (!pci_dev_is_added(dev))
+			continue;
+
+		child = dev->subordinate;
+		if (child)
+			pci_setup_bridges(child);
+	}
+
+	if (bus->self)
+		pci_setup_bridge(bus);
+}
+
 /**
  * pci_rescan_bus - Scan a PCI bus for devices
  * @bus: PCI bus to scan
@@ -3271,8 +3290,11 @@ unsigned int pci_rescan_bus(struct pci_bus *bus)
 		pci_bus_rescan_prepare(root);
 
 		max = pci_scan_child_bus(root);
+
+		pci_bus_release_root_bridge_resources(root);
 		pci_assign_unassigned_root_bus_resources(root);
 
+		pci_setup_bridges(root);
 		pci_bus_rescan_done(root);
 	} else {
 		max = pci_scan_child_bus(bus);
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index ffa81949a75f..00bdbc0ea817 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1663,6 +1663,15 @@ static void pci_bus_release_bridge_resources(struct pci_bus *bus,
 		pci_bridge_release_resources(bus, type);
 }
 
+void pci_bus_release_root_bridge_resources(struct pci_bus *root_bus)
+{
+	pci_bus_release_bridge_resources(root_bus, IORESOURCE_IO, whole_subtree);
+	pci_bus_release_bridge_resources(root_bus, IORESOURCE_MEM, whole_subtree);
+	pci_bus_release_bridge_resources(root_bus,
+					 IORESOURCE_MEM_64 | IORESOURCE_PREFETCH,
+					 whole_subtree);
+}
+
 static void pci_bus_dump_res(struct pci_bus *bus)
 {
 	struct resource *res;
-- 
2.24.1

