PCI: of: Add of_pci_preserve_config() for per-host bridge support

Add of_pci_preserve_config() to look for the "linux,pci-probe-only"
property under a specified node.  If it's not found there, look under
"of_chosen" in addition.

If the caller didn't specify a node, look under "of_chosen".

With a future patch, this will support "linux,pci-probe-only" on a per host
bridge basis based on the presence of the property in the respective PCI
host bridge DT node.

Implement of_pci_check_probe_only() using of_pci_preserve_config().

Link: https://lore.kernel.org/r/20240508174138.3630283-3-vidyas@nvidia.com
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 51e3dd0ea5abe02c4e9ce07d096f5ded30f26883..48ba95e4ab0535ec05e5a25c2af7a6651b180591 100644 (file)
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -234,27 +234,61 @@ int of_get_pci_domain_nr(struct device_node *node)
 EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
 
 /**
- * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
- *                           is present and valid
+ * of_pci_preserve_config - Return true if the boot configuration needs to
+ *                          be preserved
+ * @node: Device tree node.
+ *
+ * Look for "linux,pci-probe-only" property for a given PCI controller's
+ * node and return true if found. Also look in the chosen node if the
+ * property is not found in the given controller's node.  Having this
+ * property ensures that the kernel doesn't reconfigure the BARs and bridge
+ * windows that are already done by the platform firmware.
+ *
+ * Return: true if the property exists; false otherwise.
  */
-void of_pci_check_probe_only(void)
+bool of_pci_preserve_config(struct device_node *node)
 {
-       u32 val;
+       u32 val = 0;
        int ret;
 
-       ret = of_property_read_u32(of_chosen, "linux,pci-probe-only", &val);
+       if (!node) {
+               pr_warn("device node is NULL, trying with of_chosen\n");
+               node = of_chosen;
+       }
+
+retry:
+       ret = of_property_read_u32(node, "linux,pci-probe-only", &val);
        if (ret) {
-               if (ret == -ENODATA || ret == -EOVERFLOW)
-                       pr_warn("linux,pci-probe-only without valid value, ignoring\n");
-               return;
+               if (ret == -ENODATA || ret == -EOVERFLOW) {
+                       pr_warn("Incorrect value for linux,pci-probe-only in %pOF, ignoring\n",
+                               node);
+                       return false;
+               }
+               if (ret == -EINVAL) {
+                       if (node == of_chosen)
+                               return false;
+
+                       node = of_chosen;
+                       goto retry;
+               }
        }
 
        if (val)
+               return true;
+       else
+               return false;
+}
+
+/**
+ * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
+ *                           is present and valid
+ */
+void of_pci_check_probe_only(void)
+{
+       if (of_pci_preserve_config(of_chosen))
                pci_add_flags(PCI_PROBE_ONLY);
        else
                pci_clear_flags(PCI_PROBE_ONLY);
-
-       pr_info("PROBE_ONLY %s\n", val ? "enabled" : "disabled");
 }
 EXPORT_SYMBOL_GPL(of_pci_check_probe_only);
 

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 0df6bab385cd59910040cfb232e505ab431df683..0ad3cb69ac1b13b9b24dac5a1e6d326926a4014a 100644 (file)
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -648,6 +648,7 @@ int of_pci_get_max_link_speed(struct device_node *node);
 u32 of_pci_get_slot_power_limit(struct device_node *node,
                                u8 *slot_power_limit_value,
                                u8 *slot_power_limit_scale);
+bool of_pci_preserve_config(struct device_node *node);
 int pci_set_of_node(struct pci_dev *dev);
 void pci_release_of_node(struct pci_dev *dev);
 void pci_set_bus_of_node(struct pci_bus *bus);
@@ -686,6 +687,11 @@ of_pci_get_slot_power_limit(struct device_node *node,
        return 0;
 }
 
+static inline bool of_pci_preserve_config(struct device_node *node)
+{
+       return false;
+}
+
 static inline int pci_set_of_node(struct pci_dev *dev) { return 0; }
 static inline void pci_release_of_node(struct pci_dev *dev) { }
 static inline void pci_set_bus_of_node(struct pci_bus *bus) { }