From: Edward Pickup <Edward.Pickup@arm.com>

This patch adds a Xen boot arguments that, if enabled, causes a call to
existing code to scan pci devices enumerated by the firmware.

This will be needed ahead of dom0less support for pci passthrough on
arm.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
---

v1->v2:
* remove dead code
* don't return errors from pci_init, but report them

changes from previous series:
* remove is_pci_scan_enabled wrapper
* make pci_scan_enabled ro_after_init
* drop debug prints
* drop Edward's SOB
---
 docs/misc/xen-command-line.pandoc  |  7 +++++++
 xen/arch/arm/pci/pci-host-common.c |  1 +
 xen/arch/arm/pci/pci.c             | 30 ++++++++++++++++++++++++++++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 28a98321c7..3a59b2fce1 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -2079,6 +2079,13 @@ This option can be specified more than once (up to 8 times at present).
 
 Flag to enable or disable support for PCI passthrough
 
+### pci-scan (arm)
+> `= <boolean>`
+
+> Default: `false`
+
+Flag to enable or disable Xen PCI scan at boot.
+
 ### pcid (x86)
 > `= <boolean> | xpti=<bool>`
 
diff --git a/xen/arch/arm/pci/pci-host-common.c b/xen/arch/arm/pci/pci-host-common.c
index 487c545f3a..d3481b05eb 100644
--- a/xen/arch/arm/pci/pci-host-common.c
+++ b/xen/arch/arm/pci/pci-host-common.c
@@ -284,6 +284,7 @@ pci_host_common_probe(struct dt_device_node *dev,
     }
 
     pci_add_host_bridge(bridge);
+    pci_add_segment(bridge->segment);
 
     return bridge;
 
diff --git a/xen/arch/arm/pci/pci.c b/xen/arch/arm/pci/pci.c
index beb1f971fa..3ddee5cdbb 100644
--- a/xen/arch/arm/pci/pci.c
+++ b/xen/arch/arm/pci/pci.c
@@ -91,8 +91,14 @@ bool arch_pci_device_physdevop(void)
 bool __read_mostly pci_passthrough_enabled;
 boolean_param("pci-passthrough", pci_passthrough_enabled);
 
+/* By default pci scan is disabled. */
+static __initdata bool pci_scan_enabled;
+boolean_param("pci-scan", pci_scan_enabled);
+
 static int __init pci_init(void)
 {
+    int ret;
+
     /*
      * Enable PCI passthrough when has been enabled explicitly
      * (pci-passthrough=on).
@@ -104,9 +110,29 @@ static int __init pci_init(void)
         panic("Could not initialize PCI segment 0\n");
 
     if ( acpi_disabled )
-        return dt_pci_init();
+        ret = dt_pci_init();
     else
-        return acpi_pci_init();
+        ret = acpi_pci_init();
+
+    if ( ret < 0 )
+    {
+        printk(XENLOG_ERR "PCI: Failed to initialize PCI host bridges (rc=%d)\n", ret);
+        return 0;
+    }
+
+    if ( pci_scan_enabled )
+    {
+        ret = scan_pci_devices();
+
+        if ( ret < 0 )
+        {
+            printk(XENLOG_ERR "PCI: Failed to scan PCI devices (rc=%d)\n", ret);
+            return 0;
+        }
+
+    }
+
+    return 0;
 }
 __initcall(pci_init);
 
-- 
2.34.1