[PATCH 1/3] gpex-acpi: Support PCI link devices outside the host bridge

[Sunil V L <sunilvl@ventanamicro.com>]

Currently, PCI link devices (PNP0C0F) are always created within the
scope of the PCI root complex. However, RISC-V needs PCI link devices to
be outside the scope of the PCI host bridge to properly enable the probe
order. This matches the example given in the ACPI specification section
6.2.13.1 as well.

Enable creating link devices outside the scope of PCI root complex based
on the flag which gets set currently only for RISC-V.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
---
 hw/pci-host/gpex-acpi.c    | 29 ++++++++++++++++++++++++-----
 hw/riscv/virt-acpi-build.c |  8 +++++---
 include/hw/pci-host/gpex.h |  5 ++++-
 3 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/hw/pci-host/gpex-acpi.c b/hw/pci-host/gpex-acpi.c
index f69413ea2c..cea89a3ed8 100644
--- a/hw/pci-host/gpex-acpi.c
+++ b/hw/pci-host/gpex-acpi.c
@@ -7,7 +7,7 @@
 #include "hw/pci/pcie_host.h"
 #include "hw/acpi/cxl.h"
 
-static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq)
+static void acpi_dsdt_add_pci_route_table(Aml *scope, Aml *dev, uint32_t irq)
 {
     Aml *method, *crs;
     int i, slot_no;
@@ -45,7 +45,17 @@ static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq)
         aml_append(dev_gsi, aml_name_decl("_CRS", crs));
         method = aml_method("_SRS", 1, AML_NOTSERIALIZED);
         aml_append(dev_gsi, method);
-        aml_append(dev, dev_gsi);
+
+        /*
+         * Some architectures like RISC-V need PCI link devices created
+         * outside the scope of the PCI host bridge similar to the example
+         * given in the section 6.2.13.1 of ACPI spec 6.5.
+         */
+         if (scope) {
+            aml_append(scope, dev_gsi);
+        } else {
+            aml_append(dev, dev_gsi);
+        }
     }
 }
 
@@ -174,7 +184,11 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
                 aml_append(dev, aml_name_decl("_PXM", aml_int(numa_node)));
             }
 
-            acpi_dsdt_add_pci_route_table(dev, cfg->irq);
+            if (cfg->flags & GPEX_FLAGS_EXT_GSI_LINK) {
+                acpi_dsdt_add_pci_route_table(scope, dev, cfg->irq);
+            } else {
+                acpi_dsdt_add_pci_route_table(NULL, dev, cfg->irq);
+            }
 
             /*
              * Resources defined for PXBs are composed of the following parts:
@@ -205,7 +219,11 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
     aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
     aml_append(dev, aml_name_decl("_CCA", aml_int(1)));
 
-    acpi_dsdt_add_pci_route_table(dev, cfg->irq);
+    if (cfg->flags & GPEX_FLAGS_EXT_GSI_LINK) {
+        acpi_dsdt_add_pci_route_table(scope, dev, cfg->irq);
+    } else {
+        acpi_dsdt_add_pci_route_table(NULL, dev, cfg->irq);
+    }
 
     method = aml_method("_CBA", 0, AML_NOTSERIALIZED);
     aml_append(method, aml_return(aml_int(cfg->ecam.base)));
@@ -282,7 +300,7 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
     crs_range_set_free(&crs_range_set);
 }
 
-void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq)
+void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq, uint32_t flags)
 {
     bool ambig;
     Object *obj = object_resolve_path_type("", TYPE_GPEX_HOST, &ambig);
@@ -292,5 +310,6 @@ void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq)
     }
 
     GPEX_HOST(obj)->gpex_cfg.irq = irq;
+    GPEX_HOST(obj)->gpex_cfg.flags = flags;
     acpi_dsdt_add_gpex(scope, &GPEX_HOST(obj)->gpex_cfg);
 }
diff --git a/hw/riscv/virt-acpi-build.c b/hw/riscv/virt-acpi-build.c
index 0925528160..832a3acb8d 100644
--- a/hw/riscv/virt-acpi-build.c
+++ b/hw/riscv/virt-acpi-build.c
@@ -417,19 +417,21 @@ static void build_dsdt(GArray *table_data,
         virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
                              memmap[VIRT_VIRTIO].size,
                              VIRTIO_IRQ, 0, VIRTIO_COUNT);
-        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ);
+        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ, GPEX_FLAGS_EXT_GSI_LINK);
     } else if (socket_count == 2) {
         virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
                              memmap[VIRT_VIRTIO].size,
                              VIRTIO_IRQ + VIRT_IRQCHIP_NUM_SOURCES, 0,
                              VIRTIO_COUNT);
-        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES);
+        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES,
+                                GPEX_FLAGS_EXT_GSI_LINK);
     } else {
         virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
                              memmap[VIRT_VIRTIO].size,
                              VIRTIO_IRQ + VIRT_IRQCHIP_NUM_SOURCES, 0,
                              VIRTIO_COUNT);
-        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES * 2);
+        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES * 2,
+                                GPEX_FLAGS_EXT_GSI_LINK);
     }
 
     aml_append(dsdt, scope);
diff --git a/include/hw/pci-host/gpex.h b/include/hw/pci-host/gpex.h
index dce883573b..bee17d62c5 100644
--- a/include/hw/pci-host/gpex.h
+++ b/include/hw/pci-host/gpex.h
@@ -47,8 +47,11 @@ struct GPEXConfig {
     MemMapEntry pio;
     int         irq;
     PCIBus      *bus;
+    uint32_t    flags;
 };
 
+#define GPEX_FLAGS_EXT_GSI_LINK BIT(0)
+
 struct GPEXHost {
     /*< private >*/
     PCIExpressHost parent_obj;
@@ -71,7 +74,7 @@ struct GPEXHost {
 int gpex_set_irq_num(GPEXHost *s, int index, int gsi);
 
 void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg);
-void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq);
+void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq, uint32_t flags);
 
 #define PCI_HOST_PIO_BASE               "x-pio-base"
 #define PCI_HOST_PIO_SIZE               "x-pio-size"
-- 
2.40.1