[PATCH AUTOSEL 6.15 029/118] net: phy: mediatek: do not require syscon compatible for pio property

[Sasha Levin]

From: Frank Wunderlich <frank-w at public-files.de>

[ Upstream commit 15d7b3dfafa98270eade6c77d2336790dde0a40d ]

Current implementation requires syscon compatible for pio property
which is used for driving the switch leds on mt7988.

Replace syscon_regmap_lookup_by_phandle with of_parse_phandle and
device_node_to_regmap to get the regmap already assigned by pinctrl
driver.

Signed-off-by: Frank Wunderlich <frank-w at public-files.de>
Link: https://patch.msgid.link/20250510174933.154589-1-linux@fw-web.de
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---

**YES** This commit should be backported to stable kernel trees. ##
Analysis ### Core Issue Being Fixed The commit addresses a **device tree
compatibility problem** in the MediaTek MT7988 PHY driver. The original
code used `syscon_regmap_lookup_by_phandle()` which **requires** the
target device node to have a "syscon" compatible string. This created an
artificial requirement that forced users to modify their device trees
even when the pinctrl driver already provided the necessary regmap. ###
Code Changes Analysis The change is minimal but significant: ```c //
OLD: Forces syscon compatible requirement regmap =
syscon_regmap_lookup_by_phandle(np, "mediatek,pio"); // NEW: Works with
any regmap provider pio_np = of_parse_phandle(np, "mediatek,pio", 0);
regmap = device_node_to_regmap(pio_np); of_node_put(pio_np); ``` **Key
differences:** - `syscon_regmap_lookup_by_phandle()` requires "syscon"
compatible - `device_node_to_regmap()` works with any device that has
registered a regmap - Proper error handling maintained with
`of_node_put()` ### Why This Should Be Backported **1. Fixes Real User
Issues:** - MT7988 hardware is actively deployed (BananaPi R4,
networking devices) - Users cannot use PHY LED functionality without
modifying device trees - This affects real hardware in production, not
just development boards **2. Low Risk Change:** - Only 9 insertions, 1
deletion - No functional behavior change - same register access, same
error paths - Uses well-established kernel APIs - **Backward
compatible:** Still works with DTs that have syscon compatible -
**Forward compatible:** Also works with DTs that don't have syscon
compatible **3. High Impact Fix:** - Removes artificial device tree
constraints - Enables legitimate hardware configurations without DT
hacks - Prevents fragmentation of MT7988 ecosystem across kernel
versions - LED functionality is important for networking hardware
visibility **4. Fits Stable Criteria:** - Fixes important functionality
for users - Does not introduce new features - No architectural changes -
Confined to one driver/subsystem - Minimal regression risk ###
Comparison to Similar Commits Looking at the historical examples
provided, this commit is similar to "clk: mediatek: Get regmap without
syscon compatible check" which also moved from `syscon_node_to_regmap()`
to `device_node_to_regmap()` for the same compatibility reasons. The
pattern of removing unnecessary syscon requirements is well-established
and safe. ### Real-World Impact Without this fix, users with legitimate
device trees (where pinctrl doesn't have syscon compatible) cannot use
MT7988 PHY LED functionality. This forces them to either: 1. Patch their
device trees (not always possible in production) 2. Use older kernel
versions 3. Lose LED functionality entirely The commit solves a
**compatibility regression** rather than adding new functionality,
making it an ideal stable backport candidate.

 drivers/net/phy/mediatek/mtk-ge-soc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/mediatek/mtk-ge-soc.c b/drivers/net/phy/mediatek/mtk-ge-soc.c
index 175cf5239bba8..21975ef946d5b 100644
--- a/drivers/net/phy/mediatek/mtk-ge-soc.c
+++ b/drivers/net/phy/mediatek/mtk-ge-soc.c
@@ -7,6 +7,7 @@
 #include <linux/pinctrl/consumer.h>
 #include <linux/phy.h>
 #include <linux/regmap.h>
+#include <linux/of.h>
 
 #include "../phylib.h"
 #include "mtk.h"
@@ -1319,6 +1320,7 @@ static int mt7988_phy_probe_shared(struct phy_device *phydev)
 {
 	struct device_node *np = dev_of_node(&phydev->mdio.bus->dev);
 	struct mtk_socphy_shared *shared = phy_package_get_priv(phydev);
+	struct device_node *pio_np;
 	struct regmap *regmap;
 	u32 reg;
 	int ret;
@@ -1336,7 +1338,13 @@ static int mt7988_phy_probe_shared(struct phy_device *phydev)
 	 * The 4 bits in TPBANK0 are kept as package shared data and are used to
 	 * set LED polarity for each of the LED0.
 	 */
-	regmap = syscon_regmap_lookup_by_phandle(np, "mediatek,pio");
+	pio_np = of_parse_phandle(np, "mediatek,pio", 0);
+	if (!pio_np)
+		return -ENODEV;
+
+	regmap = device_node_to_regmap(pio_np);
+	of_node_put(pio_np);
+
 	if (IS_ERR(regmap))
 		return PTR_ERR(regmap);
 
-- 
2.39.5