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[stijn@hermes 2.6.24]$ cat udma33-40-wire-cable-misdetection.patch 
diff -Naur linux-2.6.24-old/drivers/ata/libata-core.c linux-2.6.24/drivers/ata/libata-core.c
--- linux-2.6.24-old/drivers/ata/libata-core.c  2008-04-07 23:41:18.000000000 +0200
+++ linux-2.6.24/drivers/ata/libata-core.c      2008-04-07 23:44:35.000000000 +0200
@@ -119,6 +119,10 @@
 module_param_named(noacpi, libata_noacpi, int, 0444);
 MODULE_PARM_DESC(noacpi, "Disables the use of ACPI in probe/suspend/resume when set");
 
+int libata_force_cbl = 0;
+module_param_named(force_cbl, libata_force_cbl, int, 0644);
+MODULE_PARM_DESC(force_cbl, "force PATA cable type (0=keep, 40=40c, 80=80c)");
+
 MODULE_AUTHOR("Jeff Garzik");
 MODULE_DESCRIPTION("Library module for ATA devices");
 MODULE_LICENSE("GPL");
@@ -4318,16 +4322,29 @@
         * drive side as well. Cases where we know a 40wire cable
         * is used safely for 80 are not checked here.
         */
-       if (xfer_mask & (0xF8 << ATA_SHIFT_UDMA))
-               /* UDMA/44 or higher would be available */
-               if ((ap->cbl == ATA_CBL_PATA40) ||
-                   (ata_is_40wire(dev) &&
-                   (ap->cbl == ATA_CBL_PATA_UNK ||
-                    ap->cbl == ATA_CBL_PATA80))) {
-                       ata_dev_printk(dev, KERN_WARNING,
-                                "limited to UDMA/33 due to 40-wire cable\n");
+       if (xfer_mask & (0xF8 << ATA_SHIFT_UDMA)) {
+		switch (libata_force_cbl) {
+			case 40:
+			/* limit to UDMA/33 */
+			ata_dev_printk(dev, KERN_INFO, "forcing 40c\n");
 			xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
+			break;
+			case 80:
+			/* ignore cable checks */
+			ata_dev_printk(dev, KERN_INFO, "forcing 80c\n");
+			break;
+			default:
+			/* UDMA/44 or higher would be available */
+			if ((ap->cbl == ATA_CBL_PATA40) ||
+			(ata_is_40wire(dev) &&
+			(ap->cbl == ATA_CBL_PATA_UNK ||
+			ap->cbl == ATA_CBL_PATA80))) {
+				ata_dev_printk(dev, KERN_WARNING,
+				"limited to UDMA/33 due to 40-wire cable\n");
+				xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
+			}
 		}
+	}
 
 	ata_unpack_xfermask(xfer_mask, &dev->pio_mask,
 			    &dev->mwdma_mask, &dev->udma_mask);
diff -Naur linux-2.6.24-old/drivers/ata/libata-eh.c linux-2.6.24/drivers/ata/libata-eh.c
--- linux-2.6.24-old/drivers/ata/libata-eh.c	2008-04-07 23:41:18.000000000 +0200
+++ linux-2.6.24/drivers/ata/libata-eh.c	2008-04-07 23:46:21.000000000 +0200
@@ -2296,7 +2296,25 @@
 
 	/* PDIAG- should have been released, ask cable type if post-reset */
 	if (ata_is_host_link(link) && ap->ops->cable_detect &&
-	    (ehc->i.flags & ATA_EHI_DID_RESET))
+	    (ehc->i.flags & ATA_EHI_DID_RESET)) {
+	    	ap->cbl = ap->ops->cable_detect(ap);
+		if (!(ap->flags & ATA_FLAG_SATA) && libata_force_cbl) {
+			switch (libata_force_cbl) {
+				case 40:
+				ata_port_printk(ap, KERN_INFO, "forcing 40c\n");
+				ap->cbl = ATA_CBL_PATA40;
+				break;
+				case 80:
+				ata_port_printk(ap, KERN_INFO, "forcing 80c\n");
+				ap->cbl = ATA_CBL_PATA80;
+				break;
+				default:
+				ata_port_printk(ap, KERN_WARNING,
+				"invalid force_cbl value %d\n",
+				libata_force_cbl);
+			}
+		}
+	}
 		ap->cbl = ap->ops->cable_detect(ap);
 
 	/* Configure new devices forward such that user doesn't see
diff -Naur linux-2.6.24-old/drivers/ata/libata.h linux-2.6.24/drivers/ata/libata.h
--- linux-2.6.24-old/drivers/ata/libata.h	2008-04-07 23:41:18.000000000 +0200
+++ linux-2.6.24/drivers/ata/libata.h	2008-04-07 23:46:44.000000000 +0200
@@ -60,6 +60,7 @@
 extern int atapi_passthru16;
 extern int libata_fua;
 extern int libata_noacpi;
+extern int libata_force_cbl;
 extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev);
 extern int ata_build_rw_tf(struct ata_taskfile *tf, struct ata_device *dev,
 			   u64 block, u32 n_block, unsigned int tf_flags,