PCI: pci-bridge-emul: Add support for PCI Bridge Subsystem Vendor ID capability

This is read-only capability in PCI config space. Put it between base PCI
capability and base PCI Express capability.

Driver just have to specify subsystem_vendor_id and subsystem_id fields in
emulated bridge structure and pci-bridge-emul takes care of correctly
compose PCI Bridge Subsystem Vendor ID capability.

Link: https://lore.kernel.org/r/20220222155030.988-4-pali@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: pali

drivers/pci/pci-bridge-emul.c

@@ -21,8 +21,11 @@
 #include "pci-bridge-emul.h"
 
 #define PCI_BRIDGE_CONF_END	PCI_STD_HEADER_SIZEOF
+#define PCI_CAP_SSID_SIZEOF	(PCI_SSVID_DEVICE_ID + 2)
+#define PCI_CAP_SSID_START	PCI_BRIDGE_CONF_END
+#define PCI_CAP_SSID_END	(PCI_CAP_SSID_START + PCI_CAP_SSID_SIZEOF)
 #define PCI_CAP_PCIE_SIZEOF	(PCI_EXP_SLTSTA2 + 2)
-#define PCI_CAP_PCIE_START	PCI_BRIDGE_CONF_END
+#define PCI_CAP_PCIE_START	PCI_CAP_SSID_END
 #define PCI_CAP_PCIE_END	(PCI_CAP_PCIE_START + PCI_CAP_PCIE_SIZEOF)
 
 /**
@@ -315,6 +318,25 @@ struct pci_bridge_reg_behavior pcie_cap_regs_behavior[PCI_CAP_PCIE_SIZEOF / 4] =
 	},
 };
 
+static pci_bridge_emul_read_status_t
+pci_bridge_emul_read_ssid(struct pci_bridge_emul *bridge, int reg, u32 *value)
+{
+	switch (reg) {
+	case PCI_CAP_LIST_ID:
+		*value = PCI_CAP_ID_SSVID |
+			(bridge->has_pcie ? (PCI_CAP_PCIE_START << 8) : 0);
+		return PCI_BRIDGE_EMUL_HANDLED;
+
+	case PCI_SSVID_VENDOR_ID:
+		*value = bridge->subsystem_vendor_id |
+			(bridge->subsystem_id << 16);
+		return PCI_BRIDGE_EMUL_HANDLED;
+
+	default:
+		return PCI_BRIDGE_EMUL_NOT_HANDLED;
+	}
+}
+
 /*
  * Initialize a pci_bridge_emul structure to represent a fake PCI
  * bridge configuration space. The caller needs to have initialized
@@ -341,9 +363,17 @@ int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
 	if (!bridge->pci_regs_behavior)
 		return -ENOMEM;
 
-	if (bridge->has_pcie) {
+	if (bridge->subsystem_vendor_id)
+		bridge->conf.capabilities_pointer = PCI_CAP_SSID_START;
+	else if (bridge->has_pcie)
 		bridge->conf.capabilities_pointer = PCI_CAP_PCIE_START;
+	else
+		bridge->conf.capabilities_pointer = 0;
+
+	if (bridge->conf.capabilities_pointer)
 		bridge->conf.status |= cpu_to_le16(PCI_STATUS_CAP_LIST);
+
+	if (bridge->has_pcie) {
 		bridge->pcie_conf.cap_id = PCI_CAP_ID_EXP;
 		bridge->pcie_conf.cap |= cpu_to_le16(PCI_EXP_TYPE_ROOT_PORT << 4);
 		bridge->pcie_cap_regs_behavior =
@@ -427,26 +457,28 @@ int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
 		read_op = bridge->ops->read_base;
 		cfgspace = (__le32 *) &bridge->conf;
 		behavior = bridge->pci_regs_behavior;
-	} else if (!bridge->has_pcie) {
-		/* PCIe space is not implemented, and no PCI capabilities */
-		*value = 0;
-		return PCIBIOS_SUCCESSFUL;
-	} else if (reg < PCI_CAP_PCIE_END) {
+	} else if (reg >= PCI_CAP_SSID_START && reg < PCI_CAP_SSID_END && bridge->subsystem_vendor_id) {
+		/* Emulated PCI Bridge Subsystem Vendor ID capability */
+		reg -= PCI_CAP_SSID_START;
+		read_op = pci_bridge_emul_read_ssid;
+		cfgspace = NULL;
+		behavior = NULL;
+	} else if (reg >= PCI_CAP_PCIE_START && reg < PCI_CAP_PCIE_END && bridge->has_pcie) {
 		/* Our emulated PCIe capability */
 		reg -= PCI_CAP_PCIE_START;
 		read_op = bridge->ops->read_pcie;
 		cfgspace = (__le32 *) &bridge->pcie_conf;
 		behavior = bridge->pcie_cap_regs_behavior;
-	} else if (reg < PCI_CFG_SPACE_SIZE) {
-		/* Rest of PCI space not implemented */
-		*value = 0;
-		return PCIBIOS_SUCCESSFUL;
-	} else {
+	} else if (reg >= PCI_CFG_SPACE_SIZE && bridge->has_pcie) {
 		/* PCIe extended capability space */
 		reg -= PCI_CFG_SPACE_SIZE;
 		read_op = bridge->ops->read_ext;
 		cfgspace = NULL;
 		behavior = NULL;
+	} else {
+		/* Not implemented */
+		*value = 0;
+		return PCIBIOS_SUCCESSFUL;
 	}
 
 	if (read_op)
@@ -504,24 +536,21 @@ int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
 		write_op = bridge->ops->write_base;
 		cfgspace = (__le32 *) &bridge->conf;
 		behavior = bridge->pci_regs_behavior;
-	} else if (!bridge->has_pcie) {
-		/* PCIe space is not implemented, and no PCI capabilities */
-		return PCIBIOS_SUCCESSFUL;
-	} else if (reg < PCI_CAP_PCIE_END) {
+	} else if (reg >= PCI_CAP_PCIE_START && reg < PCI_CAP_PCIE_END && bridge->has_pcie) {
 		/* Our emulated PCIe capability */
 		reg -= PCI_CAP_PCIE_START;
 		write_op = bridge->ops->write_pcie;
 		cfgspace = (__le32 *) &bridge->pcie_conf;
 		behavior = bridge->pcie_cap_regs_behavior;
-	} else if (reg < PCI_CFG_SPACE_SIZE) {
-		/* Rest of PCI space not implemented */
-		return PCIBIOS_SUCCESSFUL;
-	} else {
+	} else if (reg >= PCI_CFG_SPACE_SIZE && bridge->has_pcie) {
 		/* PCIe extended capability space */
 		reg -= PCI_CFG_SPACE_SIZE;
 		write_op = bridge->ops->write_ext;
 		cfgspace = NULL;
 		behavior = NULL;
+	} else {
+		/* Not implemented */
+		return PCIBIOS_SUCCESSFUL;
 	}
 
 	shift = (where & 0x3) * 8;

drivers/pci/pci-bridge-emul.h

@@ -132,6 +132,8 @@ struct pci_bridge_emul {
 	struct pci_bridge_reg_behavior *pcie_cap_regs_behavior;
 	void *data;
 	bool has_pcie;
+	u16 subsystem_vendor_id;
+	u16 subsystem_id;
 };
 
 enum {