[openwrt/openwrt] bcm53xx: add Tenda AC9 switch workaround

[LEDE Commits]

rmilecki pushed a commit to openwrt/openwrt.git, branch openwrt-21.02:
https://git.openwrt.org/78e4cffcd882389cb8f0bf818303f85f8d1e9c8e

commit 78e4cffcd882389cb8f0bf818303f85f8d1e9c8e
Author: Rafał Miłecki <rafal at milecki.pl>
AuthorDate: Thu Jul 31 10:25:52 2025 +0200

    bcm53xx: add Tenda AC9 switch workaround
    
    This fixes regressed support for Tenda AC9 which got broken somewhere
    between LEDE 17.01 and OpenWrt 18.06.
    
    At some point bcm47xx_nvram_gpio_pin() started working on bcm53xx
    devices and it resulted in swconfig b53 performing GPIO-based switch
    reset. It exposed some bug as switch stopped working.
    
    The problem is most likely to be some missing initialization step. Tenda
    AC9 comes with BCM53125 rev 4 (pretty common chip) but apparently needs
    some extra quirk.
    
    As a workaround (it doesn't make much sense to debug swconfig driver
    which has a working DSA replacement) simply avoid full switch reset.
    
    Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
 ...b53-add-Tenda-AC9-switch-reset-workaround.patch | 39 ++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/target/linux/bcm53xx/patches-5.4/701-b53-add-Tenda-AC9-switch-reset-workaround.patch b/target/linux/bcm53xx/patches-5.4/701-b53-add-Tenda-AC9-switch-reset-workaround.patch
new file mode 100644
index 0000000000..1b4cf5f85a
--- /dev/null
+++ b/target/linux/bcm53xx/patches-5.4/701-b53-add-Tenda-AC9-switch-reset-workaround.patch
@@ -0,0 +1,39 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal at milecki.pl>
+Date: Wed, 30 Jul 2025 12:37:12 +0000
+Subject: [PATCH] b53: add Tenda AC9 switch reset workaround
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Avoid switch reset to keep it in a working state.
+
+Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
+---
+ drivers/net/phy/b53/b53_priv.h | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+--- a/drivers/net/phy/b53/b53_priv.h
++++ b/drivers/net/phy/b53/b53_priv.h
+@@ -21,6 +21,7 @@
+ 
+ #include <linux/kernel.h>
+ #include <linux/mutex.h>
++#include <linux/of.h>
+ #include <linux/switch.h>
+ 
+ struct b53_device;
+@@ -318,6 +319,14 @@ static inline int b53_write64(struct b53
+ 
+ static inline int b53_switch_get_reset_gpio(struct b53_device *dev)
+ {
++	/*
++	 * Tenda AC9 comes with gpio2=robo_reset but performing switch reset
++	 * leaves it in a non-working state. It seems b53 swconfig driver misses
++	 * some initialization bit.
++	 */
++	if (of_machine_is_compatible("tenda,ac9"))
++		return -ENOENT;
++
+ #ifdef CONFIG_BCM47XX
+ 	enum bcm47xx_board board = bcm47xx_board_get();
+