MIPS: Malta: Let PIIX4 respond to PCI special cycles

This patch enables the PIIX4 to respond to special cycles on the PCI
bus. One such special cycle must be used in order to enter a suspend
state, and if response to it is not enabled then the suspend state will
never be entered.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6904/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/fixup-malta.c

@@ -68,6 +68,7 @@ static void malta_piix_func0_fixup(struct pci_dev *pdev)
 {
 	unsigned char reg_val;
 	u32 reg_val32;
+	u16 reg_val16;
 	/* PIIX PIRQC[A:D] irq mappings */
 	static int piixirqmap[PIIX4_FUNC0_PIRQRC_IRQ_ROUTING_MAX] = {
 		0,  0,	0,  3,
@@ -107,6 +108,11 @@ static void malta_piix_func0_fixup(struct pci_dev *pdev)
 	pci_read_config_byte(pdev, PIIX4_FUNC0_SERIRQC, &reg_val);
 	reg_val |= PIIX4_FUNC0_SERIRQC_EN | PIIX4_FUNC0_SERIRQC_CONT;
 	pci_write_config_byte(pdev, PIIX4_FUNC0_SERIRQC, reg_val);
+
+	/* Enable response to special cycles */
+	pci_read_config_word(pdev, PCI_COMMAND, &reg_val16);
+	pci_write_config_word(pdev, PCI_COMMAND,
+			      reg_val16 | PCI_COMMAND_SPECIAL);
 }
 
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_0,