[PATCH] cxl: Ignore CAPI adapters misplaced in switched slots

One should not attempt to switch a PHB into CAPI mode if there is
a switch between the PHB and the adapter. This patch modifies the
cxl driver to ignore CAPI adapters misplaced in switched slots.

Signed-off-by: Philippe Bergheaud <redacted>
---
This patch fixes Bz 142217.

 drivers/misc/cxl/pci.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index a08fcc8..2f978ed 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c

@@ -1280,6 +1280,30 @@ static void cxl_pci_remove_adapter(struct cxl *adapter)
     device_unregister(&adapter->dev);
 }
 
+#define CXL_MAX_PCIEX_PARENT 2
+
+static int cxl_slot_is_switched(struct pci_dev *dev)
+{
+    struct device_node *np;
+    int depth = 0;
+    const __be32 *prop;
+
+    if (!(np = pci_device_to_OF_node(dev))) {
+        pr_err("cxl: np = NULL\n");
+        return -ENODEV;
+    }
+    of_node_get(np);
+    while (np) {
+        np = of_get_next_parent(np);
+        prop = of_get_property(np, "device_type", NULL);
+        if (!prop || strcmp((char *)prop, "pciex"))
+            break;
+        depth++;
+    }
+    of_node_put(np);
+    return (depth > CXL_MAX_PCIEX_PARENT);
+}
+
 static int cxl_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
     struct cxl *adapter;

@@ -1291,6 +1315,11 @@ static int cxl_probe(struct pci_dev *dev, const struct pci_device_id *id)
         return -ENODEV;
     }
 
+    if (cxl_slot_is_switched(dev)) {
+        dev_dbg(&dev->dev, "cxl_init_adapter: Ignoring switched slot device\n");
+        return -ENODEV;
+    }
+
     if (cxl_verbose)
         dump_cxl_config_space(dev);