[PATCH v1] driver core: Add device links from fwnode only for the primary device

From: Saravana Kannan <saravanak@google.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, kernel-team@android.com,
	linux-kernel@vger.kernel.org
Subject: [PATCH v1] driver core: Add device links from fwnode only for the primary device
Date: Fri, 20 Mar 2020 21:54:48 -0700	[thread overview]
Message-ID: <20200321045448.15192-1-saravanak@google.com> (raw)

Sometimes, more than one (generally two) device can point to the same
fwnode.  However, only one device is set as the fwnode's device
(fwnode->dev) and can be looked up from the fwnode.

Typically, only one of these devices actually have a driver and actually
probe. If we create device links for all these devices, then the
suppliers' of these devices (with the same fwnode) will never get a
sync_state() call because one of their consumer devices will never probe
(because they don't have a driver).

So, create device links only for the device that is considered as the
fwnode's device.

One such example of this is the PCI bridge platform_device and the
corresponding pci_bus device. Both these devices will have the same
fwnode. It's the platform_device that is registered first and is set as
the fwnode's device. Also the platform_device is the one that actually
probes. Without this patch none of the suppliers of a PCI bridge
platform_device would get a sync_state() callback.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 drivers/base/core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index fc6a60998cd6..5e3cc1651c78 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2404,6 +2404,7 @@ int device_add(struct device *dev)
 	struct class_interface *class_intf;
 	int error = -EINVAL, fw_ret;
 	struct kobject *glue_dir = NULL;
+	bool is_fwnode_dev = false;
 
 	dev = get_device(dev);
 	if (!dev)
@@ -2501,8 +2502,10 @@ int device_add(struct device *dev)
 
 	kobject_uevent(&dev->kobj, KOBJ_ADD);
 
-	if (dev->fwnode && !dev->fwnode->dev)
+	if (dev->fwnode && !dev->fwnode->dev) {
 		dev->fwnode->dev = dev;
+		is_fwnode_dev = true;
+	}
 
 	/*
 	 * Check if any of the other devices (consumers) have been waiting for
@@ -2518,7 +2521,8 @@ int device_add(struct device *dev)
 	 */
 	device_link_add_missing_supplier_links();
 
-	if (fw_devlink_flags && fwnode_has_op(dev->fwnode, add_links)) {
+	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)
 			device_link_wait_for_mandatory_supplier(dev);
-- 
2.25.1.696.g5e7596f4ac-goog

