[PATCH v7 03/17] CXL/PCI: Introduce PCIe helper functions pcie_is_cxl() and pcie_is_cxl_port()

Terry Bowman
2025-02-11T19:25:29Z

CXL and AER drivers need the ability to identify CXL devices and CXL port
devices.

First, add set_pcie_cxl() with logic checking for CXL Flexbus DVSEC
presence. The CXL Flexbus DVSEC presence is used because it is required
for all the CXL PCIe devices.[1]

Add boolean 'struct pci_dev::is_cxl' with the purpose to cache the CXL
Flexbus presence.

Add pcie_is_cxl() as a macro to return 'struct pci_dev::is_cxl'.

Add pcie_is_cxl_port() to check if a device is a CXL Root Port, CXL
Upstream Switch Port, or CXL Downstream Switch Port. Also, verify the
CXL Extensions DVSEC for Ports is present.[1]

[1] CXL 3.1 Spec, 8.1.1 PCIe Designated Vendor-Specific Extended
Capability (DVSEC) ID Assignment, Table 8-2

Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
---
drivers/pci/pci.c | 13 +++++++++++++
drivers/pci/probe.c | 10 ++++++++++
include/linux/pci.h | 5 +++++
include/uapi/linux/pci_regs.h | 3 ++-
4 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 869d204a70a3..a2d8b41dd043 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5032,6 +5032,19 @@ static u16 cxl_port_dvsec(struct pci_dev *dev)
PCI_DVSEC_CXL_PORT);
}

+inline bool pcie_is_cxl(struct pci_dev *pci_dev)
+{
+ return pci_dev->is_cxl;
+}
+
+bool pcie_is_cxl_port(struct pci_dev *dev)
+{
+ if (!pcie_is_cxl(dev))
+ return false;
+
+ return (cxl_port_dvsec(dev) > 0);
+}
+
static bool cxl_sbr_masked(struct pci_dev *dev)
{
u16 dvsec, reg;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b6536ed599c3..7737b9ce7a83 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1676,6 +1676,14 @@ static void set_pcie_thunderbolt(struct pci_dev *dev)
dev->is_thunderbolt = 1;
}

+static void set_pcie_cxl(struct pci_dev *dev)
+{
+ u16 dvsec = pci_find_dvsec_capability(dev, PCI_VENDOR_ID_CXL,
+ PCI_DVSEC_CXL_FLEXBUS);
+ if (dvsec)
+ dev->is_cxl = 1;
+}
+
static void set_pcie_untrusted(struct pci_dev *dev)
{
struct pci_dev *parent = pci_upstream_bridge(dev);
@@ -2006,6 +2014,8 @@ int pci_setup_device(struct pci_dev *dev)
/* Need to have dev->cfg_size ready */
set_pcie_thunderbolt(dev);

+ set_pcie_cxl(dev);
+
set_pcie_untrusted(dev);

if (pci_is_pcie(dev))
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 1d62e785ae1f..82a0401c58d3 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -452,6 +452,7 @@ struct pci_dev {
unsigned int is_hotplug_bridge:1;
unsigned int shpc_managed:1; /* SHPC owned by shpchp */
unsigned int is_thunderbolt:1; /* Thunderbolt controller */
+ unsigned int is_cxl:1; /* Compute Express Link (CXL) */
/*
* Devices marked being untrusted are the ones that can potentially
* execute DMA attacks and similar. They are typically connected
@@ -741,6 +742,10 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
return false;
}

+bool pcie_is_cxl(struct pci_dev *pci_dev);
+
+bool pcie_is_cxl_port(struct pci_dev *dev);
+
#define for_each_pci_bridge(dev, bus) \
list_for_each_entry(dev, &bus->devices, bus_list) \
if (!pci_is_bridge(dev)) {} else
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 3445c4970e4d..dbc0f23d8c82 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -1208,9 +1208,10 @@
#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00ff0000
#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xff000000

-/* Compute Express Link (CXL r3.1, sec 8.1.5) */
+/* Compute Express Link (CXL r3.1, sec 8.1) */
#define PCI_DVSEC_CXL_PORT 3
#define PCI_DVSEC_CXL_PORT_CTL 0x0c
#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR 0x00000001
+#define PCI_DVSEC_CXL_FLEXBUS 7

#endif /* LINUX_PCI_REGS_H */
--
2.34.1