[libata] add ACPI cable detect API

Combined from two Alan Cox patches:

1) libata: ACPI checks for 80wire cable

We can use the ACPI mode information with several drivers as a hint to
cable type. If the ACPI mode set by the BIOS is faster than UDMA33 then
we know the BIOS thinks there are 80wire cables. If it doesn't set such a
mode or it has no ACPI method then we get no further information and can
rely on existing approaches

Introduce the function headers needed. Null it out for non ACPI boxes

Signed-off-by: Alan Cox <alan@redhat.com>

2) libata: ACPI checks for 80wire cable

Provide actual methods for checking if the ACPI support thinks the cable
is 80wire, or doesn't know

Signed-off-by: Alan Cox <alan@redhat.com>

Combined into a single changeset and
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/libata-acpi.c

@@ -296,6 +296,44 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
 	return rc;
 }
 
+/**
+ * ata_acpi_cbl_80wire		-	Check for 80 wire cable
+ * @ap: Port to check
+ *
+ * Return 1 if the ACPI mode data for this port indicates the BIOS selected
+ * an 80wire mode.
+ */
+
+int ata_acpi_cbl_80wire(struct ata_port *ap)
+{
+	struct ata_acpi_gtm gtm;
+	int valid = 0;
+
+	/* No _GTM data, no information */
+	if (ata_acpi_gtm(ap, &gtm) < 0)
+		return 0;
+
+	/* Split timing, DMA enabled */
+	if ((gtm.flags & 0x11) == 0x11 && gtm.drive[0].dma < 55)
+		valid |= 1;
+	if ((gtm.flags & 0x14) == 0x14 && gtm.drive[1].dma < 55)
+		valid |= 2;
+	/* Shared timing, DMA enabled */
+	if ((gtm.flags & 0x11) == 0x01 && gtm.drive[0].dma < 55)
+		valid |= 1;
+	if ((gtm.flags & 0x14) == 0x04 && gtm.drive[0].dma < 55)
+		valid |= 2;
+
+	/* Drive check */
+	if ((valid & 1) && ata_dev_enabled(&ap->link.device[0]))
+		return 1;
+	if ((valid & 2) && ata_dev_enabled(&ap->link.device[1]))
+		return 1;
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(ata_acpi_cbl_80wire);
+
 /**
  * taskfile_load_raw - send taskfile registers to host controller
  * @dev: target ATA device

include/linux/libata.h

@@ -885,6 +885,12 @@ enum {
 				  ATA_TIMING_CYCLE | ATA_TIMING_UDMA,
 };
 
+/* libata-acpi.c */
+#ifdef CONFIG_ATA_ACPI
+extern int ata_acpi_cbl_80wire(struct ata_port *ap);
+#else
+static inline int ata_acpi_cbl_80wire(struct ata_port *ap) { return 0; }
+#endif
 
 #ifdef CONFIG_PCI
 struct pci_bits {