libata: Assign OF node to the SCSI device

When we spawn a SCSI device from an ATA device in libata-scsi
the SCSI device had no relation to the device tree.

The DT binding allows us to define port nodes under a
PATA (IDE) or SATA host controller, so we can have proper device
nodes for these devices.

If OF is enabled, walk the children of the host controller node
to see if there is a valid device tree node to assign. The reg
is used to match to ID 0 for the master device and ID 1 for the
slave device.

The corresponding device tree bindings have been accepted by
the device tree maintainers.

Cc: Chris Healy <cphealy@gmail.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/libata-scsi.c

@@ -36,6 +36,7 @@
 #include <linux/suspend.h>
 #include <asm/unaligned.h>
 #include <linux/ioprio.h>
+#include <linux/of.h>
 
 #include "libata.h"
 #include "libata-transport.h"
@@ -4579,6 +4580,34 @@ int ata_scsi_add_hosts(struct ata_host *host, struct scsi_host_template *sht)
 	return rc;
 }
 
+#ifdef CONFIG_OF
+static void ata_scsi_assign_ofnode(struct ata_device *dev, struct ata_port *ap)
+{
+	struct scsi_device *sdev = dev->sdev;
+	struct device *d = ap->host->dev;
+	struct device_node *np = d->of_node;
+	struct device_node *child;
+
+	for_each_available_child_of_node(np, child) {
+		int ret;
+		u32 val;
+
+		ret = of_property_read_u32(child, "reg", &val);
+		if (ret)
+			continue;
+		if (val == dev->devno) {
+			dev_dbg(d, "found matching device node\n");
+			sdev->sdev_gendev.of_node = child;
+			return;
+		}
+	}
+}
+#else
+static void ata_scsi_assign_ofnode(struct ata_device *dev, struct ata_port *ap)
+{
+}
+#endif
+
 void ata_scsi_scan_host(struct ata_port *ap, int sync)
 {
 	int tries = 5;
@@ -4604,6 +4633,7 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 						 NULL);
 			if (!IS_ERR(sdev)) {
 				dev->sdev = sdev;
+				ata_scsi_assign_ofnode(dev, ap);
 				scsi_device_put(sdev);
 			} else {
 				dev->sdev = NULL;