linux-kernel - [PATCH v2 06/24] PCI: Always claim bridge window before its setup

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Message-Id: <20250829131113.36754-7-ilpo.jarvinen@linux.intel.com>
Date: Fri, 29 Aug 2025 16:10:55 +0300
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH v2 06/24] PCI: Always claim bridge window before its setup

When the claim of a resource fails for the full range in
pci_claim_bridge_resource(), clipping the resource to a smaller size is
attempted. If clipping is successful, the new bridge window is programmed
and only as the last step the code attempts to claim the resource again.
The order of the last two steps is slightly illogical and inconsistent with
the assignment call chains.

If claiming the bridge window after clipping fails, the bridge window that
was set up is left in place.

Rework the logic such that the bridge window is claimed before calling the
relevant bridge setup function. This make the behavior consistent with
resource fitting call chains that always assign the bridge window before
programming it.

If claiming the bridge window fails, the clipped bridge window is no longer
set up but pci_claim_bridge_resource() returns without writing the bridge
window at all.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/pci/setup-bus.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index c5fc4e2825be..b477f68b236c 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -857,9 +857,16 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
 	if ((bridge->class >> 8) != PCI_CLASS_BRIDGE_PCI)
 		return 0;

+	if (i > PCI_BRIDGE_PREF_MEM_WINDOW)
+		return -EINVAL;
+
+	/* Try to clip the resource and claim the smaller window */
 	if (!pci_bus_clip_resource(bridge, i))
 		return -EINVAL;	/* Clipping didn't change anything */

+	if (!pci_claim_resource(bridge, i))
+		return -EINVAL;
+
 	switch (i) {
 	case PCI_BRIDGE_IO_WINDOW:
 		pci_setup_bridge_io(bridge);
@@ -874,10 +881,7 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
 		return -EINVAL;
 	}

-	if (pci_claim_resource(bridge, i) == 0)
-		return 0;	/* Claimed a smaller window */
-
-	return -EINVAL;
+	return 0;
 }

 /*
-- 
2.39.5