libata:pata_atiixp: Don't use unconnected secondary port on SB600

The AMD SB600 southbridge has an PATA IDE interface, but the
secondary port has no physical connections, so is disabled in
the PCI header which makes it appear as a legacy port.

On most systems this causes no trouble, but the Amigaone X1000 has
an SB600 connected to a PowerPC SoC PCI-e root port, with an
emulated ISA bus. On this system a kernel panic occurs at boot
time during device attach for the secondary port.

Mark the port as 'dummy' to prevent this. As a bonus, disabling
this will slightly speed up booting on PC systems using an
SB600 as they will now skip 2 known empty ports.

Signed-off-by: Darren Stevens <[e-mail]>

Signed-off-by: Tejun Heo <[e-mail]>

drivers/ata/pata_atiixp.c

···
 	};
 	const struct ata_port_info *ppi[] = { &info, &info };
 
+	/* SB600 doesn't have secondary port wired */
+	if((pdev->device == PCI_DEVICE_ID_ATI_IXP600_IDE))
+		ppi[1] = &ata_dummy_port_info;
+
 	return ata_pci_bmdma_init_one(pdev, ppi, &atiixp_sht, NULL,
 				      ATA_HOST_PARALLEL_SCAN);
 }