xen: workaround missing device_type property in pci/pcie nodes

PCI buses differ from default buses in a few important ways, so it is
important to detect them properly. Normally, PCI buses are expected to
have the following property:

    device_type = "pci"

In reality, it is not always the case. To handle PCI bus nodes that
don't have the device_type property, also consider the node name: if the
node name is "pcie" or "pci" then consider the bus as a PCI bus.

This commit is based on the Linux kernel commit
d1ac0002dd29 "of: address: Work around missing device_type property in
pcie nodes".

This fixes Xen boot on RPi4. Some RPi4 kernels have the following node
on their device trees:

&pcie0 {
	pci@1,0 {
		#address-cells = <3>;
		#size-cells = <2>;
		ranges;

		reg = <0 0 0 0 0>;

		usb@1,0 {
			reg = <0x10000 0 0 0 0>;
			resets = <&reset RASPBERRYPI_FIRMWARE_RESET_ID_USB>;
		};
	};
};

The pci@1,0 node is a PCI bus. If we parse the node and its children as
a default bus, the reg property under usb@1,0 would have to be
interpreted as an address range mappable by the CPU, which is not the
case and would break.

Link: https://lore.kernel.org/xen-devel/YBmQQ3Tzu++AadKx@mattapan.m5p.com/
[fix style on commit]
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Tested-by: Elliott Mitchell <ehem+xen@m5p.com>
Tested-by: Jukka Kaartinen <jukka.kaartinen@unikie.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 18825e333edd648cb2e748a4422d338b55ec49c9..03d25a81cea8d727f9c9233268dff800e6c9f9de 100644 (file)
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -563,14 +563,28 @@ static unsigned int dt_bus_default_get_flags(const __be32 *addr)
  * PCI bus specific translator
  */
 
+static bool dt_node_is_pci(const struct dt_device_node *np)
+{
+    bool is_pci = !strcmp(np->name, "pcie") || !strcmp(np->name, "pci");
+
+    if ( is_pci )
+        printk(XENLOG_WARNING "%s: Missing device_type\n", np->full_name);
+
+    return is_pci;
+}
+
 static bool_t dt_bus_pci_match(const struct dt_device_node *np)
 {
     /*
      * "pciex" is PCI Express "vci" is for the /chaos bridge on 1st-gen PCI
      * powermacs "ht" is hypertransport
+     *
+     * If none of the device_type match, and that the node name is
+     * "pcie" or "pci", accept the device as PCI (with a warning).
      */
     return !strcmp(np->type, "pci") || !strcmp(np->type, "pciex") ||
-        !strcmp(np->type, "vci") || !strcmp(np->type, "ht");
+        !strcmp(np->type, "vci") || !strcmp(np->type, "ht") ||
+        dt_node_is_pci(np);
 }
 
 static void dt_bus_pci_count_cells(const struct dt_device_node *np,