While the resources enumerated by the CEDT.CFMWS identify a cxl_port
with host bridges as downstream ports, host bridges themselves are
upstream ports that decode to downstream ports represented by PCIe Root
Ports. Walk the PCIe Root Ports connected to a CXL Host Bridge,
identified by the ACPI0016 _HID, and add each one as a cxl_dport of the
host bridge cxl_port.
For now, component registers are not enumerated, only the first order
uport / dport relationships.
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/cxl/acpi.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 95 insertions(+), 2 deletions(-)
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 0ae7464b603d..ec324bf063b8 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -8,6 +8,48 @@
#include <linux/pci.h>
#include "cxl.h"
+struct cxl_walk_context {
+ struct device *dev;
+ struct pci_bus *root;
+ struct cxl_port *port;
+ int error;
+ int count;
+};
+
+static int match_add_root_ports(struct pci_dev *pdev, void *data)
+{
+ struct cxl_walk_context *ctx = data;
+ struct pci_bus *root_bus = ctx->root;
+ struct cxl_port *port = ctx->port;
+ int type = pci_pcie_type(pdev);
+ struct device *dev = ctx->dev;
+ u32 lnkcap, port_num;
+ int rc;
+
+ if (pdev->bus != root_bus)
+ return 0;
+ if (!pci_is_pcie(pdev))
+ return 0;
+ if (type != PCI_EXP_TYPE_ROOT_PORT)
+ return 0;
+ if (pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCAP,
+ &lnkcap) != PCIBIOS_SUCCESSFUL)
+ return 0;
+
+ /* TODO walk DVSEC to find component register base */
+ port_num = FIELD_GET(PCI_EXP_LNKCAP_PN, lnkcap);
+ rc = cxl_add_dport(port, &pdev->dev, port_num, CXL_RESOURCE_NONE);
+ if (rc) {
+ ctx->error = rc;
+ return rc;
+ }
+ ctx->count++;
+
+ dev_dbg(dev, "add dport%d: %s\n", port_num, dev_name(&pdev->dev));
+
+ return 0;
+}
+
static struct acpi_device *to_cxl_host_bridge(struct device *dev)
{
struct acpi_device *adev = to_acpi_device(dev);
@@ -17,6 +59,44 @@ static struct acpi_device *to_cxl_host_bridge(struct device *dev)
return NULL;
}
+/*
+ * A host bridge is a dport to a CFMWS decode and it is a uport to the
+ * dport (PCIe Root Ports) in the host bridge.
+ */
+static int add_host_bridge_uport(struct device *match, void *arg)
+{
+ struct acpi_device *bridge = to_cxl_host_bridge(match);
+ struct cxl_port *root_port = arg;
+ struct device *host = root_port->dev.parent;
+ struct acpi_pci_root *pci_root;
+ struct cxl_walk_context ctx;
+ struct cxl_port *port;
+
+ if (!bridge)
+ return 0;
+
+ pci_root = acpi_pci_find_root(bridge->handle);
+ if (!pci_root)
+ return -ENXIO;
+
+ /* TODO: fold in CEDT.CHBS retrieval */
+ port = devm_cxl_add_port(host, match, CXL_RESOURCE_NONE, root_port);
+ if (IS_ERR(port))
+ return PTR_ERR(port);
+ dev_dbg(host, "%s: add: %s\n", dev_name(match), dev_name(&port->dev));
+
+ ctx = (struct cxl_walk_context){
+ .dev = host,
+ .root = pci_root->bus,
+ .port = port,
+ };
+ pci_walk_bus(pci_root->bus, match_add_root_ports, &ctx);
+
+ if (ctx.count == 0)
+ return -ENODEV;
+ return ctx.error;
+}
+
static int add_host_bridge_dport(struct device *match, void *arg)
{
int rc;
@@ -49,6 +129,7 @@ static int add_host_bridge_dport(struct device *match, void *arg)
static int cxl_acpi_probe(struct platform_device *pdev)
{
+ int rc;
struct cxl_port *root_port;
struct device *host = &pdev->dev;
struct acpi_device *adev = ACPI_COMPANION(host);
@@ -58,8 +139,20 @@ static int cxl_acpi_probe(struct platform_device *pdev)
return PTR_ERR(root_port);
dev_dbg(host, "add: %s\n", dev_name(&root_port->dev));
- return bus_for_each_dev(adev->dev.bus, NULL, root_port,
- add_host_bridge_dport);
+ rc = bus_for_each_dev(adev->dev.bus, NULL, root_port,
+ add_host_bridge_dport);
+ if (rc)
+ return rc;
+
+ /*
+ * Root level scanned with host-bridge as dports, now scan host-bridges
+ * for their role as CXL uports to their CXL-capable PCIe Root Ports.
+ */
+ rc = bus_for_each_dev(adev->dev.bus, NULL, root_port,
+ add_host_bridge_uport);
+ if (rc)
+ dev_err(host, "failed to scan host bridges\n");
+ return 0;
}
static const struct acpi_device_id cxl_acpi_ids[] = {
