PCI: Add generic config accessors

Many PCI controllers' configuration space accesses are memory-mapped and
vary only in address calculation and access checks. There are 2 main
access methods: a decoded address space such as ECAM or a single address
and data register similar to x86. This implementation can support both
cases as well as be used in cases that need additional pre- or post-access
handling.

Add a new pci_ops member, map_bus, which can do access checks and any
necessary setup. It returns the address to use for the configuration space
access. The access types supported are 32-bit only accesses or correct
byte, word, or dword sized accesses.

Tested-by: Thierry Reding <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>
Reviewed-by: Thierry Reding <[e-mail]>

drivers/pci/access.c

···
 EXPORT_SYMBOL(pci_bus_write_config_word);
 EXPORT_SYMBOL(pci_bus_write_config_dword);
 
+int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
+			    int where, int size, u32 *val)
+{
+	void __iomem *addr;
+
+	addr = bus->ops->map_bus(bus, devfn, where);
+	if (!addr) {
+		*val = ~0;
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	}
+
+	if (size == 1)
+		*val = readb(addr);
+	else if (size == 2)
+		*val = readw(addr);
+	else
+		*val = readl(addr);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+EXPORT_SYMBOL_GPL(pci_generic_config_read);
+
+int pci_generic_config_write(struct pci_bus *bus, unsigned int devfn,
+			     int where, int size, u32 val)
+{
+	void __iomem *addr;
+
+	addr = bus->ops->map_bus(bus, devfn, where);
+	if (!addr)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	if (size == 1)
+		writeb(val, addr);
+	else if (size == 2)
+		writew(val, addr);
+	else
+		writel(val, addr);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+EXPORT_SYMBOL_GPL(pci_generic_config_write);
+
+int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn,
+			      int where, int size, u32 *val)
+{
+	void __iomem *addr;
+
+	addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
+	if (!addr) {
+		*val = ~0;
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	}
+
+	*val = readl(addr);
+
+	if (size <= 2)
+		*val = (*val >> (8 * (where & 3))) & ((1 << (size * 8)) - 1);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+EXPORT_SYMBOL_GPL(pci_generic_config_read32);
+
+int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn,
+			       int where, int size, u32 val)
+{
+	void __iomem *addr;
+	u32 mask, tmp;
+
+	addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
+	if (!addr)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	if (size == 4) {
+		writel(val, addr);
+		return PCIBIOS_SUCCESSFUL;
+	} else {
+		mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8));
+	}
+
+	tmp = readl(addr) & mask;
+	tmp |= val << ((where & 0x3) * 8);
+	writel(tmp, addr);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+EXPORT_SYMBOL_GPL(pci_generic_config_write32);
+
 /**
  * pci_bus_set_ops - Set raw operations of pci bus
  * @bus:	pci bus struct

include/linux/pci.h

···
 /* Low-level architecture-dependent routines */
 
 struct pci_ops {
+	void __iomem *(*map_bus)(struct pci_bus *bus, unsigned int devfn, int where);
 	int (*read)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *val);
 	int (*write)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 val);
 };
···
 			      int where, u16 val);
 int pci_bus_write_config_dword(struct pci_bus *bus, unsigned int devfn,
 			       int where, u32 val);
+
+int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
+			    int where, int size, u32 *val);
+int pci_generic_config_write(struct pci_bus *bus, unsigned int devfn,
+			    int where, int size, u32 val);
+int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn,
+			      int where, int size, u32 *val);
+int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn,
+			       int where, int size, u32 val);
+
 struct pci_ops *pci_bus_set_ops(struct pci_bus *bus, struct pci_ops *ops);
 
 static inline int pci_read_config_byte(const struct pci_dev *dev, int where, u8 *val)