diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index d260d92..5bcbb6e 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -120,14 +120,27 @@
 	<programlisting>
 void (*set_piomode) (struct ata_port *, struct ata_device *);
 void (*set_dmamode) (struct ata_port *, struct ata_device *);
-void (*post_set_mode) (struct ata_port *ap);
+void (*post_set_mode) (struct ata_port *);
+unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int);
 	</programlisting>
 
 	<para>
 	Hooks called prior to the issue of SET FEATURES - XFER MODE
-	command.  dev->pio_mode is guaranteed to be valid when
-	->set_piomode() is called, and dev->dma_mode is guaranteed to be
-	valid when ->set_dmamode() is called.  ->post_set_mode() is
+	command.  The optional ->mode_filter() hook is called when libata
+	has built a mask of the possible modes. This is passed to the 
+	->mode_filter() function which should return a mask of valid modes
+	after filtering those unsuitable due to hardware limits. It is not
+	valid to use this interface to add modes.
+	</para>
+	<para>
+	dev->pio_mode and dev->dma_mode are guaranteed to be valid when
+	->set_piomode() and when ->set_dmamode() is called. The timings for
+	any other drive sharing the cable will also be valid at this point.
+	That is the library records the decisions for the modes of each
+	drive on a channel before it attempts to set any of them.
+	</para>
+	<para>
+	->post_set_mode() is
 	called unconditionally, after the SET FEATURES - XFER MODE
 	command completes successfully.
 	</para>
@@ -230,6 +243,32 @@
 
 	</sect2>
 
+	<sect2><title>Private tuning method</title>
+	<programlisting>
+void (*set_mode) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+	By default libata performs drive and controller tuning in
+	accordance with the ATA timing rules and also applies blacklists
+	and cable limits. Some controllers need special handling and have
+	custom tuning rules, typically raid controllers that use ATA
+	commands but do not actually do drive timing.
+	</para>
+
+	<warning>
+	<para>
+	This hook should not be used to replace the standard controller
+	tuning logic when a controller has quirks. Replacing the default
+	tuning logic in that case would bypass handling for drive and
+	bridge quirks that may be important to data reliability. If a
+	controller needs to filter the mode selection it should use the
+	mode_filter hook instead.
+	</para>
+	</warning>
+
+	</sect2>
+
 	<sect2><title>Reset ATA bus</title>
 	<programlisting>
 void (*phy_reset) (struct ata_port *ap);
diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 4165944..b1ddf40 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1818,7 +1818,7 @@
  */
 static void ata_set_mode(struct ata_port *ap)
 {
-	int i, rc;
+	int i, rc, used_dma = 0;
 
 	/* step 1: calculate xfer_mask */
 	for (i = 0; i < ATA_MAX_DEVICES; i++) {
@@ -1836,6 +1836,9 @@
 		dma_mask = ata_pack_xfermask(0, dev->mwdma_mask, dev->udma_mask);
 		dev->pio_mode = ata_xfer_mask2mode(pio_mask);
 		dev->dma_mode = ata_xfer_mask2mode(dma_mask);
+
+		if (dev->dma_mode)
+			used_dma = 1;
 	}
 
 	/* step 2: always set host PIO timings */
@@ -1857,6 +1860,17 @@
 			goto err_out;
 	}
 
+	/*
+	 *	Record simplex status. If we selected DMA then the other
+	 *	host channels are not permitted to do so.
+	 */
+
+	if (used_dma && (ap->host_set->flags & ATA_HOST_SIMPLEX))
+		ap->host_set->simplex_claimed = 1;
+
+	/*
+	 *	Chip specific finalisation
+	 */
 	if (ap->ops->post_set_mode)
 		ap->ops->post_set_mode(ap);
 
@@ -2646,13 +2660,14 @@
  */
 static void ata_dev_xfermask(struct ata_port *ap, struct ata_device *dev)
 {
+	struct ata_host_set *hs = ap->host_set;
 	unsigned long xfer_mask;
 	int i;
 
 	xfer_mask = ata_pack_xfermask(ap->pio_mask, ap->mwdma_mask,
 				      ap->udma_mask);
 
-	/* use port-wide xfermask for now */
+	/* FIXME: Use port-wide xfermask for now */
 	for (i = 0; i < ATA_MAX_DEVICES; i++) {
 		struct ata_device *d = &ap->device[i];
 		if (!ata_dev_present(d))
@@ -2662,12 +2677,23 @@
 		xfer_mask &= ata_id_xfermask(d->id);
 		if (ata_dma_blacklisted(d))
 			xfer_mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
+		/* Apply cable rule here. Don't apply it early because when
+		   we handle hot plug the cable type can itself change */
+		if (ap->cbl == ATA_CBL_PATA40)
+			xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
 	}
 
 	if (ata_dma_blacklisted(dev))
 		printk(KERN_WARNING "ata%u: dev %u is on DMA blacklist, "
 		       "disabling DMA\n", ap->id, dev->devno);
 
+	if (hs->flags & ATA_HOST_SIMPLEX) {
+		if (hs->simplex_claimed)
+			xfer_mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
+	}
+	if (ap->ops->mode_filter)
+		xfer_mask = ap->ops->mode_filter(ap, dev, xfer_mask);
+
 	ata_unpack_xfermask(xfer_mask, &dev->pio_mask, &dev->mwdma_mask,
 			    &dev->udma_mask);
 }
@@ -4531,6 +4557,7 @@
 	host_set->mmio_base = ent->mmio_base;
 	host_set->private_data = ent->private_data;
 	host_set->ops = ent->port_ops;
+	host_set->flags = ent->host_set_flags;
 
 	/* register each port bound to this device */
 	for (i = 0; i < ent->n_ports; i++) {
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6a9316c..0d61357 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -294,6 +294,9 @@
 	unsigned int		n_ports;
 	void			*private_data;
 	const struct ata_port_operations *ops;
+	unsigned long		flags;
+	int			simplex_claimed;	/* Keep seperate in case we
+							   ever need to do this locked */
 	struct ata_port *	ports[0];
 };
 
@@ -423,6 +426,7 @@
 
 	void (*set_piomode) (struct ata_port *, struct ata_device *);
 	void (*set_dmamode) (struct ata_port *, struct ata_device *);
+	unsigned long (*mode_filter) (const struct ata_port *, struct ata_device *, unsigned long);
 
 	void (*tf_load) (struct ata_port *ap, const struct ata_taskfile *tf);
 	void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);