linux-kernel - [PATCH] of/address: Add error logging for of_match

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Message-ID: <20250811095342.2383808-1-quic_zhenhuah@quicinc.com>
Date: Mon, 11 Aug 2025 17:53:42 +0800
From: Zhenhua Huang <quic_zhenhuah@...cinc.com>
To: <robh@...nel.org>, <saravanak@...gle.com>
CC: <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Zhenhua
 Huang" <quic_zhenhuah@...cinc.com>
Subject: [PATCH] of/address: Add error logging for of_match_bus() in address translation path

The change introduced in
commit 045b14ca5c36 ("of: WARN on deprecated #address-cells/#size-cells handling")
triggers a warning on the direct ancestor node when translating properties
like "iommu-addresses"/"reg". However, it fails to issue a warning if the
ancestor’s ancestor is missing the required cells.
For instance, if node_c lacks the necessary properties, no warning will be
generated. Potential issues will be trigger further.
node_c {
		//NO WARN
	node_b {
		//WARN on missing of "address-cells" and "size-cells"
		node_a {
			xxx = <memory_reion>  //contains "iommu-addresses"
		}
	}
}

Since of_match_bus() is now expected to succeed in traslation path,
routine __of_translate_address. Print an error message would help in
identifying cases where it fails, making such issues easier to diagnose.

Signed-off-by: Zhenhua Huang <quic_zhenhuah@...cinc.com>
---
 drivers/of/address.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index f0f8f0dd191c..cd33ab64ccf3 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -515,8 +515,10 @@ static u64 __of_translate_address(struct device_node *node,
 	if (parent == NULL)
 		return OF_BAD_ADDR;
 	bus = of_match_bus(parent);
-	if (!bus)
+	if (!bus) {
+		pr_err("of_match_bus failed for device node(%pOF)\n", parent);
 		return OF_BAD_ADDR;
+	}
 
 	/* Count address cells & copy address locally */
 	bus->count_cells(dev, &na, &ns);
@@ -560,8 +562,10 @@ static u64 __of_translate_address(struct device_node *node,
 
 		/* Get new parent bus and counts */
 		pbus = of_match_bus(parent);
-		if (!pbus)
+		if (!pbus) {
+			pr_err("of_match_bus failed for device node(%pOF)\n", parent);
 			return OF_BAD_ADDR;
+		}
 		pbus->count_cells(dev, &pna, &pns);
 		if (!OF_CHECK_COUNTS(pna, pns)) {
 			pr_err("Bad cell count for %pOF\n", dev);
-- 
2.34.1