[PATCH v2 03/14] cxl/pci: Introduce helper functions pcie_is_cxl() and pcie_is_cxl_port()

[Terry Bowman <terry.bowman@amd.com>]

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 port 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>
---
 drivers/pci/pci.c             | 14 ++++++++++++++
 drivers/pci/probe.c           | 10 ++++++++++
 include/linux/pci.h           |  4 ++++
 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 7d85c04fbba2..c1b243aec61c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5034,6 +5034,20 @@ static u16 cxl_port_dvsec(struct pci_dev *dev)
 					 PCI_DVSEC_CXL_PORT);
 }
 
+bool pcie_is_cxl_port(struct pci_dev *dev)
+{
+	if (!pcie_is_cxl(dev))
+		return false;
+
+	if ((pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT) &&
+	    (pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM) &&
+	    (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM))
+		return false;
+
+	return cxl_port_dvsec(dev);
+}
+EXPORT_SYMBOL_GPL(pcie_is_cxl_port);
+
 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 4f68414c3086..9324eb345f11 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1631,6 +1631,14 @@ 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;
@@ -1945,6 +1953,8 @@ 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);
 
 	/* "Unknown power state" */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 106ac83e3a7b..d3b1af9fb273 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -443,6 +443,7 @@ 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;               /* CXL alternate protocol */
 	/*
 	 * Devices marked being untrusted are the ones that can potentially
 	 * execute DMA attacks and similar. They are typically connected
@@ -743,6 +744,9 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
 	return false;
 }
 
+#define pcie_is_cxl(dev) (dev->is_cxl)
+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 12323b3334a9..5df6c74963c5 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -1186,9 +1186,10 @@
 #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