hw/pci: Add pcie_count_ds_port() and pcie_find_port_first() helpers

These two helpers enable host bridges to operate differently depending on
the number of downstream ports, in particular if there is only a single
port.

Useful for CXL where HDM address decoders are allowed to be implicit in
the host bridge if there is only a single root port.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20230227153128.8164-2-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/hw/pci/pcie_port.c b/hw/pci/pcie_port.c
index 000633fec1..20ff2b39e8 100644
--- a/hw/pci/pcie_port.c
+++ b/hw/pci/pcie_port.c
@@ -161,6 +161,44 @@ PCIDevice *pcie_find_port_by_pn(PCIBus *bus, uint8_t pn)
     return NULL;
 }
 
+/* Find first port in devfn number order */
+PCIDevice *pcie_find_port_first(PCIBus *bus)
+{
+    int devfn;
+
+    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {
+        PCIDevice *d = bus->devices[devfn];
+
+        if (!d || !pci_is_express(d) || !d->exp.exp_cap) {
+            continue;
+        }
+
+        if (object_dynamic_cast(OBJECT(d), TYPE_PCIE_PORT)) {
+            return d;
+        }
+    }
+
+    return NULL;
+}
+
+int pcie_count_ds_ports(PCIBus *bus)
+{
+    int dsp_count = 0;
+    int devfn;
+
+    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {
+        PCIDevice *d = bus->devices[devfn];
+
+        if (!d || !pci_is_express(d) || !d->exp.exp_cap) {
+            continue;
+        }
+        if (object_dynamic_cast(OBJECT(d), TYPE_PCIE_PORT)) {
+            dsp_count++;
+        }
+    }
+    return dsp_count;
+}
+
 static bool pcie_slot_is_hotpluggbale_bus(HotplugHandler *plug_handler,
                                           BusState *bus)
 {
diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
index 6c40e3733f..90e6cf45b8 100644
--- a/include/hw/pci/pcie_port.h
+++ b/include/hw/pci/pcie_port.h
@@ -41,6 +41,8 @@ struct PCIEPort {
 void pcie_port_init_reg(PCIDevice *d);
 
 PCIDevice *pcie_find_port_by_pn(PCIBus *bus, uint8_t pn);
+PCIDevice *pcie_find_port_first(PCIBus *bus);
+int pcie_count_ds_ports(PCIBus *bus);
 
 #define TYPE_PCIE_SLOT "pcie-slot"
 OBJECT_DECLARE_SIMPLE_TYPE(PCIESlot, PCIE_SLOT)