powerpc/of/pci: Rewrite pci_parse_of_flags

The existing code uses bunch of hardcoded values from the PCI Bus
Binding to IEEE Std 1275 spec; and it does so in quite non-obvious
way.

This defines fields from the cell#0 of the "reg" property of a PCI
device and uses them for parsing.

This should cause no behavioral change.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[mpe: Unsplit some 80/81 char lines, space the code with some newlines]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190829084417.71873-1-aik@ozlabs.ru

arch/powerpc/kernel/pci_of_scan.c

@@ -34,31 +34,75 @@ static u32 get_int_prop(struct device_node *np, const char *name, u32 def)
  * pci_parse_of_flags - Parse the flags cell of a device tree PCI address
  * @addr0: value of 1st cell of a device tree PCI address.
  * @bridge: Set this flag if the address is from a bridge 'ranges' property
+ *
+ * PCI Bus Binding to IEEE Std 1275-1994
+ *
+ * Bit#            33222222 22221111 11111100 00000000
+ *                 10987654 32109876 54321098 76543210
+ * phys.hi cell:   npt000ss bbbbbbbb dddddfff rrrrrrrr
+ * phys.mid cell:  hhhhhhhh hhhhhhhh hhhhhhhh hhhhhhhh
+ * phys.lo cell:   llllllll llllllll llllllll llllllll
+ *
+ * where:
+ * n        is 0 if the address is relocatable, 1 otherwise
+ * p        is 1 if the addressable region is "prefetchable", 0 otherwise
+ * t        is 1 if the address is aliased (for non-relocatable I/O),
+ *          below 1 MB (for Memory),or below 64 KB (for relocatable I/O).
+ * ss       is the space code, denoting the address space:
+ *              00 denotes Configuration Space
+ *              01 denotes I/O Space
+ *              10 denotes 32-bit-address Memory Space
+ *              11 denotes 64-bit-address Memory Space
+ * bbbbbbbb is the 8-bit Bus Number
+ * ddddd    is the 5-bit Device Number
+ * fff      is the 3-bit Function Number
+ * rrrrrrrr is the 8-bit Register Number
  */
+#define OF_PCI_ADDR0_SPACE(ss)		(((ss)&3)<<24)
+#define OF_PCI_ADDR0_SPACE_CFG		OF_PCI_ADDR0_SPACE(0)
+#define OF_PCI_ADDR0_SPACE_IO		OF_PCI_ADDR0_SPACE(1)
+#define OF_PCI_ADDR0_SPACE_MMIO32	OF_PCI_ADDR0_SPACE(2)
+#define OF_PCI_ADDR0_SPACE_MMIO64	OF_PCI_ADDR0_SPACE(3)
+#define OF_PCI_ADDR0_SPACE_MASK		OF_PCI_ADDR0_SPACE(3)
+#define OF_PCI_ADDR0_RELOC		(1UL<<31)
+#define OF_PCI_ADDR0_PREFETCH		(1UL<<30)
+#define OF_PCI_ADDR0_ALIAS		(1UL<<29)
+#define OF_PCI_ADDR0_BUS		0x00FF0000UL
+#define OF_PCI_ADDR0_DEV		0x0000F800UL
+#define OF_PCI_ADDR0_FN			0x00000700UL
+#define OF_PCI_ADDR0_BARREG		0x000000FFUL
+
 unsigned int pci_parse_of_flags(u32 addr0, int bridge)
 {
-	unsigned int flags = 0;
+	unsigned int flags = 0, as = addr0 & OF_PCI_ADDR0_SPACE_MASK;
 
-	if (addr0 & 0x02000000) {
+	if (as == OF_PCI_ADDR0_SPACE_MMIO32 || as == OF_PCI_ADDR0_SPACE_MMIO64) {
 		flags = IORESOURCE_MEM | PCI_BASE_ADDRESS_SPACE_MEMORY;
-		flags |= (addr0 >> 22) & PCI_BASE_ADDRESS_MEM_TYPE_64;
-		if (flags & PCI_BASE_ADDRESS_MEM_TYPE_64)
-			flags |= IORESOURCE_MEM_64;
-		flags |= (addr0 >> 28) & PCI_BASE_ADDRESS_MEM_TYPE_1M;
-		if (addr0 & 0x40000000)
-			flags |= IORESOURCE_PREFETCH
-				 | PCI_BASE_ADDRESS_MEM_PREFETCH;
+
+		if (as == OF_PCI_ADDR0_SPACE_MMIO64)
+			flags |= PCI_BASE_ADDRESS_MEM_TYPE_64 | IORESOURCE_MEM_64;
+
+		if (addr0 & OF_PCI_ADDR0_ALIAS)
+			flags |= PCI_BASE_ADDRESS_MEM_TYPE_1M;
+
+		if (addr0 & OF_PCI_ADDR0_PREFETCH)
+			flags |= IORESOURCE_PREFETCH |
+				 PCI_BASE_ADDRESS_MEM_PREFETCH;
+
 		/* Note: We don't know whether the ROM has been left enabled
 		 * by the firmware or not. We mark it as disabled (ie, we do
 		 * not set the IORESOURCE_ROM_ENABLE flag) for now rather than
 		 * do a config space read, it will be force-enabled if needed
 		 */
-		if (!bridge && (addr0 & 0xff) == 0x30)
+		if (!bridge && (addr0 & OF_PCI_ADDR0_BARREG) == PCI_ROM_ADDRESS)
 			flags |= IORESOURCE_READONLY;
-	} else if (addr0 & 0x01000000)
+
+	} else if (as == OF_PCI_ADDR0_SPACE_IO)
 		flags = IORESOURCE_IO | PCI_BASE_ADDRESS_SPACE_IO;
+
 	if (flags)
 		flags |= IORESOURCE_SIZEALIGN;
+
 	return flags;
 }