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