Index: linux-2.6.16/drivers/scsi/libata-core.c
===================================================================
--- linux-2.6.16.orig/drivers/scsi/libata-core.c	2006-06-18 15:23:49.000000000 +0200
+++ linux-2.6.16/drivers/scsi/libata-core.c	2006-06-18 20:57:13.000000000 +0200
@@ -4706,6 +4706,7 @@
 				   struct ata_queued_cmd *qc)
 {
 	u8 status, host_stat = 0;
+    int i;
 
 	VPRINTK("ata%u: protocol %d task_state %d\n",
 		ap->id, qc->tf.protocol, ap->hsm_task_state);
@@ -4752,9 +4753,25 @@
 	}
 
 	/* check altstatus */
-	status = ata_altstatus(ap);
-	if (status & ATA_BUSY)
-		goto idle_irq;
+	if (qc->tf.command == ATA_CMD_SET_FEATURES &&
+			qc->tf.feature == SETFEATURES_XFER) {
+		/* With some configurations (PATA VIA and CDR-6S48), the
+		 * ata_altstatus take some times (~ 3us) to become not busy.
+		 * Without this quirk, it is impossible to set the xfer mode.
+		 */
+		for (i = 0; ata_altstatus(ap) & ATA_BUSY; i++) {
+			if (i > 10)
+				goto idle_irq;
+			udelay(1);
+		}
+
+		if (i)
+			ata_port_printk(ap, KERN_WARNING, "ata_altstatus take %dus\n", i);
+	} else {
+		status = ata_altstatus(ap);
+		if (status & ATA_BUSY)
+			goto idle_irq;
+	}
 
 	/* check main status, clearing INTRQ */
 	status = ata_chk_status(ap);