Hi everyone,
I'm trying to add support for the D-Link DAP series business APs made by Edimax (e.g. DAP-2662 here).
They are QCA9563 + Wave2, using the elx-header image type wrapped into wrgg03 image.
When booting initramfs, the device will perform a factory reset roughly 1 second after uboot hands over execution to the kernel, and in the stock firmware, a few messages related to ath79-wdt are output around that time of boot:
...
m25p80 spi0.0: w25q128 (16384 Kbytes)
Creating 9 MTD partitions on "spi0.0":
0x000000000000-0x000001000000 : "ALL"
0x000000000000-0x000000040000 : "Bootloader"
0x000000040000-0x000000050000 : "Config"
0x000000050000-0x000000d70000 : "Kernel"
0x000000250000-0x000000d70000 : "user"
0x000000d70000-0x000000e70000 : "userdata"
0x000000e70000-0x000000f70000 : "manufacture"
0x000000f70000-0x000000ff0000 : "storage"
0x000000ff0000-0x000001000000 : "ART"
libphy: ag71xx_mdio: probed
eth0: Atheros AG71xx at 0xb9000000, irq 4
Disable 803x az function.
ag71xx 19000000.ethernet: connected to PHY at 19000000.mdio:03 [uid=004dd074, driver=Atheros 8031/8033 ethernet]
Registered button device:reset, gpio:2,code:408,index:10
ath79_wdt: WDOG_REG_CTRL: 0x0
Error: Driver 'ath79-wdt' is already registered, aborting...
u32 classifier
Actions configured
...
Looking at the datasheets, there is a hardware watchdog in ath79 at 0x18060008, and even a dt binding which I tried to use:
&wdt {
status = "okay";
timeout-sec = <1>;
};
Even with status = 'disabled' there is no difference, the boot will interrupt after about 1 second:
...
[ 0.620020] 1 squashfs-split partitions found on MTD device rootfs
[ 0.626446] 0x000000b50000-0x000000e20000 : "rootfs_data"
[ 0.633585] 0x000000e70000-0x000000f70000 : "manufacture"
[ 0.640065] 0x000000f70000-0x000000ff0000 : "storage"
[ 0.647628] 0x000000ff0000-0x000001000000 : "art"
[ 0.658567] libphy: Fixed MDIO Bus: probed
[ 0.666312] ag71xx 19000000.eth: invalid MAC address, using random address
▒
U-Boot 1.1.4-g1466e5c4 (Mar 13 2018 - 13:39:31)
ELX version: 1.0.3
ap152_ar8033 - Dragonfly 1.0DRAM:
sri
ath_ddr_initial_config(278): (ddr2 init)
ath_sys_frequency: cpu 775 ddr 650 ahb 258
Tap values = (0xf, 0xf, 0xf, 0xf)
128 MB
...
I also disabled any GPIOs, disabled JTAG pins etc. to make sure there is no hardware short-circuit etc. causing a reset.
So it seems, maybe the watchdog configuration just happens too late in the boot process?
I also tried to fiddle with the pinctrl-single driver to overwrite the watchdog enable bit via gpio-keys, and delete the &wdt node declared in the dtsi altogether:
/delete-node/ &wdt;
wdtpinmux: pinmux@18060008 {
compatible = "pinctrl-single";
reg = <0x18060008 0x8>;
#size-cells = <0>;
pinctrl-single,bit-per-mux;
pinctrl-single,register-width = <32>;
pinctrl-single,function-mask = <0x1>;
#pinctrl-cells = <2>;
wdt_disable: pinmux_wdt_disable {
pinctrl-single,bits = <0x0 0x0 0x3>;
};
};
keys {
compatible = "gpio-keys";
pinctrl-names = "default", "nowdt";
pinctrl-0 = <&jtag_disable_pins>;
pinctrl-1 = <&wdt_disable>;
reset {
label = "reset";
linux,code = <KEY_RESTART>;
gpios = <&gpio 2 GPIO_ACTIVE_HIGH>;
};
};
But this does not work either, it still reboots, from both initramfs, or when writing the image to flash.
I also verified with OKLI loader, which usually says SYSTEM HALTED when it could not find a partition, and it reboots as well, so I'm quite certain this is the ath79 wathchog. Although in the uboot shell, the registers (including reason for last reboot) will be set to 0 already (wdt is probably just enabled right before handing over control to the extracted kernel image, since uboot could not periodically reset it without heavy modifications).
Any suggestions on how to make sure the wdt reset happens even earlier in the boot process?
Any further input on this is highly appreciated 
