[PATCH] realtek: ZyXEL GS1900-48: drop gpio-restart

[Sander Vanheule]

On Tue, 2022-02-22 at 23:39 +0100, Birger Koblitz wrote:
> Hi,
> 
> the information on the external GPIO resetting the board of
> the Zyxel GS1900-48 comes from the hardware configuration
> reported by the stock firmware. It says:
> GS1900# show board
> [...]
> ====== Reset =================
> Type: GPIO
> GPIO: EXT_5
> [...]
> Using the rtk gpio commands in u-boot this can be confirmed.

Can you list the commands that you used to test this? My bootloader only supports "rtk
network ..." and "cst pinSet ...".


> On 22/02/2022 23:00, Sander Vanheule wrote:
> > On Mon, 2022-02-21 at 21:23 +0100, Birger Koblitz wrote:
> > > Hi,
> > > > 
> > > > I just checked with my multimeter, and while the GPIO5 on the RTL8231 does go
> > > > high/low
> > > > when I set the output high/low from Linux, my device certainly doesn't reset. The
> > > > other
> > > > GPIO lines on the chip do work, since SFP modules are correctly detected.
> > > > 
> > > > Birger, just to be sure, can you confirm that your device does reset with GPIO5 on
> > > > the
> > > > RTL8231?
> > > 
> > > Yes, it does.There is a warning, but then it reliably resets. That was why I left it
> > > in as is.
> > 
> > I had another hard look at my board, to check if something may be wrong physically,
> > but I
> > cannot find anything. My device's board looks identical to the pictures on the switch
> > wiki
> > [1], which I think you uploaded earlier.
> > 
> > There is some reset logic on the board [2], but I cannot figure out how GPIO5 would be
> > connected to it electrically. Unless I missed a via connecting to that pin on the
> > RTL8231,
> > GPIO5 only appears to lead to TP2. GPIO5/TP2 does not appear to be connected
> > electrically
> > to any part of the circuit next to SW1. I could add a bodge wire to connect TP2 to pad
> > U25:3, but gpio-restart should really work on unmodified hardware.
> > 
> > [1] https://svanheule.net/switches/gs1900-48#board_details
> > [2] https://svanheule.net/switches/gs1900-48#hard_reset_circuit


Having another look at the source code of gpio-restart, the WARNING-s I reported in the
patch's commit message occur at the following points of the GPIO output waveform:

     |< 100ms >|< 100 ms >|<   3000 ms   >|< Restart failed
_____|_________|          |_______________|__ [ active ]
_____X         \__________/                   [inactive]
      |        |          |               |
      |        |          |               ^ WARN @ drivers/power/reset/gpio-restart.c:46
      |        |          |
      |        |          ^ WARN @ drivers/gpio/gpiolib.c:3098
      |        ^ WARN @ drivers/gpio/gpiolib.c:3098
      |
      ^ Restart should already occur here


If everything is set up correctly, the system should restart before execution reaches the
point where a warning can be emitted. If you say that you see a warning (any at all),
AFAICT that means gpio-restart is not working.

As they say, the proof of the pudding is in the eating, so I soldered a jumper wire
between the RTL8231's GPIO5 pin (U38:25) and the line driven by the hard reset button
(U25:3) [https://svanheule.net/switches/gs1900-48#hard_reset_circuit].
As expected from the analysis above, this results in a system rebooting without _any_
warning (using an initramfs from yesterday's snapshot builds):

root at OpenWrt:/# reboot
root at OpenWrt:/# [  185.092891] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  185.101879] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  185.111835] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  185.120484] rtl83xx_fib4_del: found a route with id 1, nh-id 0
[  185.127681] rtl83xx-switch switch at 1b000000: unknown nexthop, id 0
[  185.149505] rtl83xx-switch switch at 1b000000: unknown nexthop, id 0
[  185.157262] rtl83xx_fib4_del: found a route with id 2, nh-id 0
[  185.164418] rtl83xx-switch switch at 1b000000: unknown nexthop, id 0
[  185.173391] rtl83xx_fib4_del: no such gateway: 0.0.0.0
[  185.225492] device lan01 left promiscuous mode
[  185.230976] switch: port 1(lan01) entered disabled state
...
[  187.735562] device lan50 left promiscuous mode
[  187.741075] switch: port 50(lan50) entered disabled state
[  187.794104] in rtl838x_eth_stop
[  187.797945] rtl838x-eth 1b00a300.ethernet eth0: Link is Down
[  188.329431] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.337562] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.345649] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.353736] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.543709] rtl83xx_fib4_del: no such gateway: 0.0.0.0
[  188.549982] rtl83xx_fib4_del: no such gateway: 0.0.0.0
[  188.559077] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.567226] rtl83xx_fib_event: FIB_RULE ADD/DELL for IPv6 not supported
[  188.576283] rtl83xx_fib4_del: no such gateway: 0.0.0.0
[  188.582679] rtl83xx_fib4_del: no such gateway: 0.0.0.0
[  192.871878] reboot: Restarting system


U-Boot Version: 2.0.0.59413 (Jul 08 2015 - 10:01:28)

CPU:   750MHz
DRAM:  128 MB
FLASH: 16 MB
Model: ZyXEL_GS1900_48
SN:    S182L05000541


Best,
Sander