atiixp.c: add cable detection support for ATI IDE

IDE HDD does not work if it uses a 40-pin PATA cable on ATI chipset.
This patch fixes the bug.
Signed-off-by: Conke Hu <conke.hu@amd.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/pci/atiixp.c

@@ -291,8 +291,12 @@ fast_ata_pio:
 
 static void __devinit init_hwif_atiixp(ide_hwif_t *hwif)
 {
+	u8 udma_mode = 0;
+	u8 ch = hwif->channel;
+	struct pci_dev *pdev = hwif->pci_dev;
+
 	if (!hwif->irq)
-		hwif->irq = hwif->channel ? 15 : 14;
+		hwif->irq = ch ? 15 : 14;
 
 	hwif->autodma = 0;
 	hwif->tuneproc = &atiixp_tuneproc;
@@ -308,8 +312,12 @@ static void __devinit init_hwif_atiixp(ide_hwif_t *hwif)
 	hwif->mwdma_mask = 0x06;
 	hwif->swdma_mask = 0x04;
 
-	/* FIXME: proper cable detection needed */
-	hwif->udma_four = 1;
+	pci_read_config_byte(pdev, ATIIXP_IDE_UDMA_MODE + ch, &udma_mode);
+	if ((udma_mode & 0x07) >= 0x04 || (udma_mode & 0x70) >= 0x40)
+		hwif->udma_four = 1;
+	else
+		hwif->udma_four = 0;
+
 	hwif->ide_dma_host_on = &atiixp_ide_dma_host_on;
 	hwif->ide_dma_host_off = &atiixp_ide_dma_host_off;
 	hwif->ide_dma_check = &atiixp_dma_check;