MIPS: Malta: Setup PM I/O region on boot

This patch ensures that the kernel sets a sane base address for the
PIIX4 PM I/O register region during boot. Without this the kernel may
not successfully claim the region as a resource if the bootloader didn't
configure the region. With this patch the kernel will always succeed
with:

  pci 0000:00:0a.3: quirk: [io  0x1000-0x103f] claimed by PIIX4 ACPI

The lack of the resource claiming is easily reproducible without this
patch using current versions of QEMU.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Tested-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6641/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mips-boards/piix4.h

@@ -50,4 +50,9 @@
 #define PIIX4_FUNC1_IDETIM_SECONDARY_HI		0x43
 #define   PIIX4_FUNC1_IDETIM_SECONDARY_HI_IDE_DECODE_EN	(1 << 7)
 
+/* Power Management Configuration Space */
+#define PIIX4_FUNC3_PMBA			0x40
+#define PIIX4_FUNC3_PMREGMISC			0x80
+#define   PIIX4_FUNC3_PMREGMISC_EN			(1 << 0)
+
 #endif /* __ASM_MIPS_BOARDS_PIIX4_H */

arch/mips/pci/fixup-malta.c

@@ -51,6 +51,19 @@ int pcibios_plat_dev_init(struct pci_dev *dev)
 	return 0;
 }
 
+static void malta_piix_func3_base_fixup(struct pci_dev *dev)
+{
+	/* Set a sane PM I/O base address */
+	pci_write_config_word(dev, PIIX4_FUNC3_PMBA, 0x1000);
+
+	/* Enable access to the PM I/O region */
+	pci_write_config_byte(dev, PIIX4_FUNC3_PMREGMISC,
+			      PIIX4_FUNC3_PMREGMISC_EN);
+}
+
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
+			malta_piix_func3_base_fixup);
+
 static void malta_piix_func0_fixup(struct pci_dev *pdev)
 {
 	unsigned char reg_val;