[PATCH] PCI: Fix pcim_intx() recursive calls

[Philipp Stanner]

pci_intx() calls into pcim_intx() in managed mode, i.e., when
pcim_enable_device() had been called. This recursive call causes a bug
by re-registering the device resource in the release callback.

This is the same phenomenon that made it necessary to implement some
functionality a second time, see __pcim_request_region().

Implement __pcim_intx() to bypass the hybrid nature of pci_intx() on
driver detach.

Fixes: https://lore.kernel.org/all/20240708214656.4721-1-Ashish.Kalra@amd.c=
om/
Reported-by: Ashish Kalra <Ashish.Kalra@xxxxxxx>
Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx>
---
Hi Ashish,
I hacked down this fix that should be applyable on top.
Could you maybe have a first quick look whether this fixes the issue?
---
 drivers/pci/devres.c | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
index 2f0379a4e58f..dcef049b72fe 100644
--- a/drivers/pci/devres.c
+++ b/drivers/pci/devres.c
@@ -408,12 +408,31 @@ static inline bool mask_contains_bar(int mask, int ba=
r)
 	return mask & BIT(bar);
 }
=20
+/*
+ * This is a copy of pci_intx() used to bypass the problem of occuring
+ * recursive function calls due to the hybrid nature of pci_intx().
+ */
+static void __pcim_intx(struct pci_dev *pdev, int enable)
+{
+	u16 pci_command, new;
+
+	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
+
+	if (enable)
+		new =3D pci_command & ~PCI_COMMAND_INTX_DISABLE;
+	else
+		new =3D pci_command | PCI_COMMAND_INTX_DISABLE;
+
+	if (new !=3D pci_command)
+		pci_write_config_word(pdev, PCI_COMMAND, new);
+}
+
 static void pcim_intx_restore(struct device *dev, void *data)
 {
 	struct pci_dev *pdev =3D to_pci_dev(dev);
 	struct pcim_intx_devres *res =3D data;
=20
-	pci_intx(pdev, res->orig_intx);
+	__pcim_intx(pdev, res->orig_intx);
 }
=20
 static struct pcim_intx_devres *get_or_create_intx_devres(struct device *d=
ev)
@@ -443,7 +462,6 @@ static struct pcim_intx_devres *get_or_create_intx_devr=
es(struct device *dev)
  */
 int pcim_intx(struct pci_dev *pdev, int enable)
 {
-	u16 pci_command, new;
 	struct pcim_intx_devres *res;
=20
 	res =3D get_or_create_intx_devres(&pdev->dev);
@@ -451,16 +469,7 @@ int pcim_intx(struct pci_dev *pdev, int enable)
 		return -ENOMEM;
=20
 	res->orig_intx =3D !enable;
-
-	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
-
-	if (enable)
-		new =3D pci_command & ~PCI_COMMAND_INTX_DISABLE;
-	else
-		new =3D pci_command | PCI_COMMAND_INTX_DISABLE;
-
-	if (new !=3D pci_command)
-		pci_write_config_word(pdev, PCI_COMMAND, new);
+	__pcim_intx(pdev, enable);
=20
 	return 0;
 }
--=20
2.45.0