linux-kernel - [PATCH v1 3/4] PCI: Change extend_bridge_window() to set resource size directly

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Message-ID: <PSXP216MB04386BA48874B56BC5CB0292803C0@PSXP216MB0438.KORP216.PROD.OUTLOOK.COM>
Date:   Mon, 6 Jan 2020 15:47:46 +0000
From:   Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
Subject: [PATCH v1 3/4] PCI: Change extend_bridge_window() to set resource
 size directly

Change extend_bridge_window() to set resource size directly instead of
using additional resource lists.

Because additional resource lists are optional resources, any algorithm
that requires guaranteed allocation that uses them cannot be guaranteed
to work.

Remove the resource from add_list, as a zero-sized additional resource
is redundant.

Update comment in pci_bus_distribute_available_resources() to reflect
the above changes.

Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
---
 drivers/pci/setup-bus.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index de43815be..0c51f4937 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1836,7 +1836,7 @@ static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
 				 struct list_head *add_list,
 				 resource_size_t new_size)
 {
-	struct pci_dev_resource *dev_res;
+	resource_size_t add_size;
 
 	if (res->parent)
 		return;
@@ -1844,17 +1844,10 @@ static void adjust_bridge_window(struct pci_dev *bridge, struct resource *res,
 	if (resource_size(res) >= new_size)
 		return;
 
-	dev_res = res_to_dev_res(add_list, res);
-	if (!dev_res)
-		return;
-
-	/* Is there room to extend the window? */
-	if (new_size - resource_size(res) <= dev_res->add_size)
-		return;
-
-	dev_res->add_size = new_size - resource_size(res);
-	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
-		&dev_res->add_size);
+	add_size = new_size - resource_size(res);
+	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
+	res->end = res->start + new_size - 1;
+	remove_from_list(add_list, res);
 }
 
 static void pci_bus_distribute_available_resources(struct pci_bus *bus,
@@ -1889,11 +1882,9 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
 		mmio_pref.start = min(ALIGN(mmio_pref.start, align),
 			mmio_pref.end + 1);
 
-	/*
-	 * Update additional resource list (add_list) to fill all the
-	 * extra resource space available for this port except the space
-	 * calculated in __pci_bus_size_bridges() which covers all the
-	 * devices currently connected to the port and below.
+        /*
+	 * Now that we have adjusted for alignment, update the bridge window
+	 * resources to fill as much remaining resource space as possible.
 	 */
 	adjust_bridge_window(bridge, io_res, add_list, resource_size(&io));
 	adjust_bridge_window(bridge, mmio_res, add_list, resource_size(&mmio));
-- 
2.24.1