[PATCH v2] bus: fsl-mc: drop the fwnode links of the dpmacs nodes

From: Vincent Jardin <vjardin@free.fr>

A DPMAC node under dpmacs/ is never the fwnode of any device:
  the fsl-mc bus creates dpmac.N objects without one,
  then dpaa2-mac finds its node in dpmacs/ at connect time.

fw_devlink therefore attaches the supplier links of those nodes (phys, ...)
to the nearest ancestor device, the fsl-mc bus, as SYNC_STATE_ONLY proxies.

device_link_add() refuses such a link once the consumer has probed, and
fw_devlink logs the refusal as an error.

On an LX2160A board with 4x25G DPMACs for which phys = <&serdes_1 N>,
the Serdes PHY binds after the bus and then at every boot it shows:

  fsl_mc_bus 80c000000.fsl-mc: Failed to create device link (0x180) with supplier 1ea0000.phy for /soc/fsl-mc@80c000000/dpmacs/ethernet@3

once per port!

To fix it, when the root MC bus probes, purge the fwnode links of every
child of its dpmacs node, so fw_devlink has no supplier link left to
proxy to the bus and no longer tries to create those device links.

Signed-off-by: Vincent Jardin <vjardin@free.fr>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com> # LX2160ARDB
---
The dpmacs node is the documented child of the
fsl-mc node: Documentation/devicetree/bindings/misc/fsl,qoriq-mc.yaml
(and bindings/net/fsl,qoriq-mc-dpmac.yaml for its DPMAC subnodes).

Changes in v2:
- Improve commit log (Christophe)
- Collect Ioana's Reviewed-by and Tested-by
- Link to v1: https://lore.kernel.org/r/20260928-for-upstream-fsl-mc-dpmac-fwnode-links-v1-1-b8976244b38b@free.fr (local)
---
 drivers/bus/fsl-mc/fsl-mc-bus.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index 5878eafd8d44..0c37b6780c84 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c

@@ -11,6 +11,7 @@
 #define pr_fmt(fmt) "fsl-mc: " fmt
 
 #include <linux/module.h>
+#include <linux/fwnode.h>
 #include <linux/of_device.h>
 #include <linux/of_address.h>
 #include <linux/ioport.h>

@@ -1033,6 +1034,20 @@ static int fsl_mc_firmware_check(struct platform_device *pdev)
 	return 0;
 }
 
+static void fsl_mc_purge_dpmac_fwnode_links(struct device *dev)
+{
+	struct device_node *dpmacs, *child;
+
+	dpmacs = of_get_child_by_name(dev->of_node, "dpmacs");
+	if (!dpmacs)
+		return;
+
+	for_each_child_of_node(dpmacs, child)
+		fwnode_links_purge(of_fwnode_handle(child));
+
+	of_node_put(dpmacs);
+}
+
 /*
  * fsl_mc_bus_probe - callback invoked when the root MC bus is being
  * added

@@ -1134,6 +1149,8 @@ static int fsl_mc_bus_probe(struct platform_device *pdev)
 						&mc->num_translation_ranges);
 		if (error < 0)
 			goto error_cleanup_mc_io;
+
+		fsl_mc_purge_dpmac_fwnode_links(&pdev->dev);
 	}
 
 	error = dprc_get_container_id(mc_io, 0, &container_id);

---
base-commit: 7b3b0598c00e67f2df85d0b4cd99eaa3be6c9bfd
change-id: 20260928-for-upstream-fsl-mc-dpmac-fwnode-links-622b8eadb98a

Best regards,
-- 
Vincent Jardin [off-list ref]