[RFC,qemu,6/6] hw/pci-bridge/cxl-upstream: Add properties to control link speed and width

Commit Message

Jonathan Cameron July 12, 2024, 12:24 p.m. UTC

To establish performance characteristics of a CXL device when used via a
particular CXL topology (root ports, switches, end points) it is necessary
to set the appropriate link speed and width in the PCI Express capability
structure.  Provide x-speed and x-link properties for this.

Signed-off-by: Jonathan Cameron <[e-mail]>
---
 include/hw/pci-bridge/cxl_upstream_port.h | 4 ++++
 hw/pci-bridge/cxl_upstream.c              | 6 ++++++
 2 files changed, 10 insertions(+)

Patch

diff --git a/include/hw/pci-bridge/cxl_upstream_port.h b/include/hw/pci-bridge/cxl_upstream_port.h
index 12635139f6..f208397ffe 100644
--- a/include/hw/pci-bridge/cxl_upstream_port.h
+++ b/include/hw/pci-bridge/cxl_upstream_port.h
@@ -12,6 +12,10 @@  typedef struct CXLUpstreamPort {
     /*< public >*/
     CXLComponentState cxl_cstate;
     CXLCCI swcci;
+
+    PCIExpLinkSpeed speed;
+    PCIExpLinkWidth width;
+
     DOECap doe_cdat;
     uint64_t sn;
 } CXLUpstreamPort;
diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
index e51221a5f3..e673d69220 100644
--- a/hw/pci-bridge/cxl_upstream.c
+++ b/hw/pci-bridge/cxl_upstream.c
@@ -11,6 +11,7 @@ 
 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "hw/qdev-properties.h"
+#include "hw/qdev-properties-system.h"
 #include "hw/pci/msi.h"
 #include "hw/pci/pcie.h"
 #include "hw/pci/pcie_port.h"
@@ -100,6 +101,7 @@  static void cxl_usp_reset(DeviceState *qdev)
 
     pci_bridge_reset(qdev);
     pcie_cap_deverr_reset(d);
+    pcie_cap_fill_link_ep_usp(d, usp->width, usp->speed);
     latch_registers(usp);
 }
 
@@ -363,6 +365,10 @@  static void cxl_usp_exitfn(PCIDevice *d)
 static Property cxl_upstream_props[] = {
     DEFINE_PROP_UINT64("sn", CXLUpstreamPort, sn, UI64_NULL),
     DEFINE_PROP_STRING("cdat", CXLUpstreamPort, cxl_cstate.cdat.filename),
+    DEFINE_PROP_PCIE_LINK_SPEED("x-speed", CXLUpstreamPort,
+                                speed, PCIE_LINK_SPEED_32),
+    DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLUpstreamPort,
+                                width, PCIE_LINK_WIDTH_16),
     DEFINE_PROP_END_OF_LIST()
 };