PCI: aardvark: Add support for AER registers on emulated bridge

Aardvark controller supports Advanced Error Reporting configuration
registers.

Export these registers on the emulated root bridge via new .read_ext() and
.write_ext() methods.

Note that in the Advanced Error Reporting Capability header the offset to
the next Extended Capability header is set, but it is not documented in
Armada 3700 Functional Specification. Since this change adds support only
for Advanced Error Reporting, explicitly clear PCI_EXT_CAP_NEXT bits in AER
capability header.

Now the pcieport driver correctly detects AER support and allows PCIe AER
driver to start receiving ERR interrupts. Kernel log now says:

  pcieport 0000:00:00.0: AER: enabled with IRQ 52

Link: https://lore.kernel.org/r/20220524132827.8837-2-kabel@kernel.orgSigned-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/pci-aardvark.c

@@ -33,6 +33,7 @@
 #define PCIE_CORE_CMD_STATUS_REG				0x4
 #define PCIE_CORE_DEV_REV_REG					0x8
 #define PCIE_CORE_PCIEXP_CAP					0xc0
+#define PCIE_CORE_PCIERR_CAP					0x100
 #define PCIE_CORE_ERR_CAPCTL_REG				0x118
 #define     PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX			BIT(5)
 #define     PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX_EN			BIT(6)
@@ -944,11 +945,89 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
 	}
 }
 
+static pci_bridge_emul_read_status_t
+advk_pci_bridge_emul_ext_conf_read(struct pci_bridge_emul *bridge,
+				   int reg, u32 *value)
+{
+	struct advk_pcie *pcie = bridge->data;
+
+	switch (reg) {
+	case 0:
+		*value = advk_readl(pcie, PCIE_CORE_PCIERR_CAP + reg);
+
+		/*
+		 * PCI_EXT_CAP_NEXT bits are set to offset 0x150, but Armada
+		 * 3700 Functional Specification does not document registers
+		 * at those addresses.
+		 *
+		 * Thus we clear PCI_EXT_CAP_NEXT bits to make Advanced Error
+		 * Reporting Capability header the last Extended Capability.
+		 * If we obtain documentation for those registers in the
+		 * future, this can be changed.
+		 */
+		*value &= 0x000fffff;
+		return PCI_BRIDGE_EMUL_HANDLED;
+
+	case PCI_ERR_UNCOR_STATUS:
+	case PCI_ERR_UNCOR_MASK:
+	case PCI_ERR_UNCOR_SEVER:
+	case PCI_ERR_COR_STATUS:
+	case PCI_ERR_COR_MASK:
+	case PCI_ERR_CAP:
+	case PCI_ERR_HEADER_LOG + 0:
+	case PCI_ERR_HEADER_LOG + 4:
+	case PCI_ERR_HEADER_LOG + 8:
+	case PCI_ERR_HEADER_LOG + 12:
+	case PCI_ERR_ROOT_COMMAND:
+	case PCI_ERR_ROOT_STATUS:
+	case PCI_ERR_ROOT_ERR_SRC:
+		*value = advk_readl(pcie, PCIE_CORE_PCIERR_CAP + reg);
+		return PCI_BRIDGE_EMUL_HANDLED;
+
+	default:
+		return PCI_BRIDGE_EMUL_NOT_HANDLED;
+	}
+}
+
+static void
+advk_pci_bridge_emul_ext_conf_write(struct pci_bridge_emul *bridge,
+				    int reg, u32 old, u32 new, u32 mask)
+{
+	struct advk_pcie *pcie = bridge->data;
+
+	switch (reg) {
+	/* These are W1C registers, so clear other bits */
+	case PCI_ERR_UNCOR_STATUS:
+	case PCI_ERR_COR_STATUS:
+	case PCI_ERR_ROOT_STATUS:
+		new &= mask;
+		fallthrough;
+
+	case PCI_ERR_UNCOR_MASK:
+	case PCI_ERR_UNCOR_SEVER:
+	case PCI_ERR_COR_MASK:
+	case PCI_ERR_CAP:
+	case PCI_ERR_HEADER_LOG + 0:
+	case PCI_ERR_HEADER_LOG + 4:
+	case PCI_ERR_HEADER_LOG + 8:
+	case PCI_ERR_HEADER_LOG + 12:
+	case PCI_ERR_ROOT_COMMAND:
+	case PCI_ERR_ROOT_ERR_SRC:
+		advk_writel(pcie, new, PCIE_CORE_PCIERR_CAP + reg);
+		break;
+
+	default:
+		break;
+	}
+}
+
 static const struct pci_bridge_emul_ops advk_pci_bridge_emul_ops = {
 	.read_base = advk_pci_bridge_emul_base_conf_read,
 	.write_base = advk_pci_bridge_emul_base_conf_write,
 	.read_pcie = advk_pci_bridge_emul_pcie_conf_read,
 	.write_pcie = advk_pci_bridge_emul_pcie_conf_write,
+	.read_ext = advk_pci_bridge_emul_ext_conf_read,
+	.write_ext = advk_pci_bridge_emul_ext_conf_write,
 };
 
 /*