linux-kernel - [PATCH 11/23] PCI: Log reset and restore of resources

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Message-Id: <20251219174036.16738-12-ilpo.jarvinen@linux.intel.com>
Date: Fri, 19 Dec 2025 19:40:24 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: linux-pci@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	linux-kernel@...r.kernel.org
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH 11/23] PCI: Log reset and restore of resources

PCI resource fitting and assignment is complicated to track because it
performs many actions without any logging. One of these is resource
reset (zeroing the resource) and the restore during the multi-passed
resource fitting algorithm.

Resource reset does not play well with the other PCI code if the code
later wants to reattempt assignment of that resource, knowing that a
resource was left into the reset state without a pairing restore is
useful for understanding issues that show up as resource assignment
failures.

Add pci_dbg() to both reset and restore to be better able to track
what's going on within the resource fitting algorithm.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/pci/setup-bus.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 403139d8c86a..a5b6c555a45b 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -136,6 +136,9 @@ static resource_size_t get_res_add_align(struct list_head *head,
 static void restore_dev_resource(struct pci_dev_resource *dev_res)
 {
 	struct resource *res = dev_res->res;
+	struct pci_dev *dev = dev_res->dev;
+	int idx = pci_resource_num(dev, res);
+	const char *res_name = pci_resource_name(dev, idx);
 
 	if (WARN_ON_ONCE(res->parent))
 		return;
@@ -143,6 +146,8 @@ static void restore_dev_resource(struct pci_dev_resource *dev_res)
 	res->start = dev_res->start;
 	res->end = dev_res->end;
 	res->flags = dev_res->flags;
+
+	pci_dbg(dev, "%s %pR: resource restored\n", res_name, res);
 }
 
 /*
@@ -384,15 +389,18 @@ bool pci_resource_is_optional(const struct pci_dev *dev, int resno)
 	return false;
 }
 
-static inline void reset_resource(struct pci_dev *dev, struct resource *res)
+static void reset_resource(struct pci_dev *dev, struct resource *res)
 {
 	int idx = pci_resource_num(dev, res);
+	const char *res_name = pci_resource_name(dev, idx);
 
 	if (pci_resource_is_bridge_win(idx)) {
 		res->flags |= IORESOURCE_UNSET;
 		return;
 	}
 
+	pci_dbg(dev, "%s %pR: resetting resource\n", res_name, res);
+
 	res->start = 0;
 	res->end = 0;
 	res->flags = 0;
-- 
2.39.5