PCI: pci-bridge-emul: Extend pci_bridge_emul_init() with flags

Depending on the capabilities of the PCI controller/platform, the
PCI-to-PCI bridge emulation behavior might need to be different. For
example, on platforms that use the pci-mvebu code, we currently don't
support prefetchable memory BARs, so the corresponding fields in the
PCI-to-PCI bridge configuration space should be read-only.

To implement this, extend pci_bridge_emul_init() to take a "flags"
argument, with currently one flag supported:

PCI_BRIDGE_EMUL_NO_PREFETCHABLE_BAR

that will make the prefetchable memory base and limit registers
read-only.

The pci-mvebu and pci-aardvark drivers are updated accordingly.

Fixes: 1f08673eef123 ("PCI: mvebu: Convert to PCI emulated bridge config space")
Reported-by: Luís Mendes <[e-mail]>
Reported-by: Leigh Brown <[e-mail]>
Tested-by: Leigh Brown <[e-mail]>
Tested-by: Luis Mendes <[e-mail]>
Signed-off-by: Thomas Petazzoni <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Cc: [e-mail]
Cc: Luís Mendes <[e-mail]>
Cc: Leigh Brown <[e-mail]>

drivers/pci/controller/pci-aardvark.c

···
 	bridge->data = pcie;
 	bridge->ops = &advk_pci_bridge_emul_ops;
 
-	pci_bridge_emul_init(bridge);
+	pci_bridge_emul_init(bridge, 0);
 
 }
 

drivers/pci/controller/pci-mvebu.c

···
 	bridge->data = port;
 	bridge->ops = &mvebu_pci_bridge_emul_ops;
 
-	pci_bridge_emul_init(bridge);
+	pci_bridge_emul_init(bridge, PCI_BRIDGE_EMUL_NO_PREFETCHABLE_BAR);
 }
 
 static inline struct mvebu_pcie *sys_to_pcie(struct pci_sys_data *sys)

drivers/pci/pci-bridge-emul.c

···
  * (typically at least vendor, device, revision), the ->ops pointer,
  * and optionally ->data and ->has_pcie.
  */
-int pci_bridge_emul_init(struct pci_bridge_emul *bridge)
+int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
+			 unsigned int flags)
 {
 	bridge->conf.class_revision |= PCI_CLASS_BRIDGE_PCI << 16;
 	bridge->conf.header_type = PCI_HEADER_TYPE_BRIDGE;
···
 			kfree(bridge->pci_regs_behavior);
 			return -ENOMEM;
 		}
+	}
+
+	if (flags & PCI_BRIDGE_EMUL_NO_PREFETCHABLE_BAR) {
+		bridge->pci_regs_behavior[PCI_PREF_MEMORY_BASE / 4].ro = ~0;
+		bridge->pci_regs_behavior[PCI_PREF_MEMORY_BASE / 4].rw = 0;
 	}
 
 	return 0;

drivers/pci/pci-bridge-emul.h

···
 	bool has_pcie;
 };
 
-int pci_bridge_emul_init(struct pci_bridge_emul *bridge);
+enum {
+	PCI_BRIDGE_EMUL_NO_PREFETCHABLE_BAR = BIT(0),
+};
+
+int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
+			 unsigned int flags);
 void pci_bridge_emul_cleanup(struct pci_bridge_emul *bridge);
 
 int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,