driver core: Fix handling of fw_devlink=permissive

When commit 8375e74f ("driver core: Add fw_devlink kernel
commandline option") added fw_devlink, it didn't implement "permissive"
mode correctly.

That commit got the device links flags correct to make sure unprobed
suppliers don't block the probing of a consumer. However, if a consumer
is waiting for mandatory suppliers to register, that could still block a
consumer from probing.

This commit fixes that by making sure in permissive mode, all suppliers
to a consumer are treated as a optional suppliers. So, even if a
consumer is waiting for suppliers to register and link itself (using the
DL_FLAG_SYNC_STATE_ONLY flag) to the supplier, the consumer is never
blocked from probing.

Fixes: 8375e74f ("driver core: Add fw_devlink kernel commandline option")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200331022832.209618-1-saravanak@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -2370,6 +2370,11 @@ u32 fw_devlink_get_flags(void)
 	return fw_devlink_flags;
 }
 
+static bool fw_devlink_is_permissive(void)
+{
+	return fw_devlink_flags == DL_FLAG_SYNC_STATE_ONLY;
+}
+
 /**
  * device_add - add device to device hierarchy.
  * @dev: device.
@@ -2524,7 +2529,7 @@ int device_add(struct device *dev)
 	if (fw_devlink_flags && is_fwnode_dev &&
 	    fwnode_has_op(dev->fwnode, add_links)) {
 		fw_ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
-		if (fw_ret == -ENODEV)
+		if (fw_ret == -ENODEV && !fw_devlink_is_permissive())
 			device_link_wait_for_mandatory_supplier(dev);
 		else if (fw_ret)
 			device_link_wait_for_optional_supplier(dev);