libahci_platform: Fail when PHY required but PHY support disabled

ahci_platform_get_resources handles resource management for
platform AHCI drivers, including getting a possible PHY
from the device tree. Since not all drivers need a PHY, it
ignores -ENODEV and -ENOSYS from devm_get_phy. However, when
the PHY subsystem is mistakenly disabled, -ENOSYS can be
returned even when a PHY is needed.

This patch modifies the -ENOSYS case to check if a "phys"
device tree node exists. If it exists, then clearly the PHY
subsystem is mistakenly disabled and the driver cannot work,
ahci_platform_get_resources will fail and propagate the error.
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libahci_platform.c

@@ -250,8 +250,13 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev)
 	if (IS_ERR(hpriv->phy)) {
 		rc = PTR_ERR(hpriv->phy);
 		switch (rc) {
-		case -ENODEV:
 		case -ENOSYS:
+			/* No PHY support. Check if PHY is required. */
+			if (of_find_property(dev->of_node, "phys", NULL)) {
+				dev_err(dev, "couldn't get sata-phy: ENOSYS\n");
+				goto err_out;
+			}
+		case -ENODEV:
 			/* continue normally */
 			hpriv->phy = NULL;
 			break;