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-pass 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 in 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@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251219174036.16738-12-ilpo.jarvinen@linux.intel.com

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 403139d8c86acea9fff6886a7cea5805120dfc9c..a5b6c555a45bfb5534da21277507d665e2c2bbd0 100644 (file)
--- 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;