PCI: pci-bridge-emul: Re-arrange register tests

Re-arrange the tests for which sets of registers are being accessed so that
it is easier to add further regions later. No functional change.

[pali: Fix reading old value in pci_bridge_emul_conf_write]
Link: https://lore.kernel.org/r/20220222155030.988-2-pali@kernel.org
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: Russell King

drivers/pci/pci-bridge-emul.c

@@ -422,25 +422,25 @@ int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
 	__le32 *cfgspace;
 	const struct pci_bridge_reg_behavior *behavior;
 
-	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_END) {
-		*value = 0;
-		return PCIBIOS_SUCCESSFUL;
-	}
-
-	if (!bridge->has_pcie && reg >= PCI_BRIDGE_CONF_END) {
+	if (reg < PCI_BRIDGE_CONF_END) {
+		/* Emulated PCI space */
+		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;
-	}
-
-	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_START) {
+	} else if (reg < PCI_CAP_PCIE_END) {
+		/* 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 {
-		read_op = bridge->ops->read_base;
-		cfgspace = (__le32 *) &bridge->conf;
-		behavior = bridge->pci_regs_behavior;
+		/* Beyond our PCIe space */
+		*value = 0;
+		return PCIBIOS_SUCCESSFUL;
 	}
 
 	if (read_op)
@@ -484,11 +484,27 @@ int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
 	__le32 *cfgspace;
 	const struct pci_bridge_reg_behavior *behavior;
 
-	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_END)
-		return PCIBIOS_SUCCESSFUL;
+	ret = pci_bridge_emul_conf_read(bridge, reg, 4, &old);
+	if (ret != PCIBIOS_SUCCESSFUL)
+		return ret;
 
-	if (!bridge->has_pcie && reg >= PCI_BRIDGE_CONF_END)
+	if (reg < PCI_BRIDGE_CONF_END) {
+		/* Emulated PCI space */
+		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) {
+		/* 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 {
+		return PCIBIOS_SUCCESSFUL;
+	}
 
 	shift = (where & 0x3) * 8;
 
@@ -501,21 +517,6 @@ int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
 	else
 		return PCIBIOS_BAD_REGISTER_NUMBER;
 
-	ret = pci_bridge_emul_conf_read(bridge, reg, 4, &old);
-	if (ret != PCIBIOS_SUCCESSFUL)
-		return ret;
-
-	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_START) {
-		reg -= PCI_CAP_PCIE_START;
-		write_op = bridge->ops->write_pcie;
-		cfgspace = (__le32 *) &bridge->pcie_conf;
-		behavior = bridge->pcie_cap_regs_behavior;
-	} else {
-		write_op = bridge->ops->write_base;
-		cfgspace = (__le32 *) &bridge->conf;
-		behavior = bridge->pci_regs_behavior;
-	}
-
 	/* Keep all bits, except the RW bits */
 	new = old & (~mask | ~behavior[reg / 4].rw);