[meta-xilinx] u-boot SPL boot fail with CONFIG_HW_WATCHDOG

Mike Looijmans mike.looijmans at topic.nl
Wed Mar 26 02:26:14 PDT 2014

For a custom board with an external GPIO controlled watchdog, I tried adding 
watchdog support to u-boot. (using master-next from u-boot-xlnx)

The watchdog support works (I'm using a LED for now until the real hardware 
arrives), I just defined CONFIG_HW_WATCHDOG and added a reset routine that 
bitbangs the GPIO registers which should feed the watchdog. I can see the LED 
blink, so the GPIO routines appear to work well.

However, this causes the board to fail to boot the kernel.

If I define CONFIG_HW_WATCHDOG and leave the hw_watchdog_*() methods empty, so 
that there SHOULD be no effect, the kernel will not boot and the system hangs 
immediately after "Starting kernel...". Removing the define from the board 
config makes that problem go away. If I call the GPIO routines from the board 
code in u-boot, the kernel still boots fine too.

The zynq has no support for any WATCHDOG yet, so I have no idea what could 
cause this behaviour.

I'm looking for a possible cause. Any ideas?

Related question #1: Would you be interested in a patch that adds GPIO support 
for the Zynq to u-boot?

Related question #2: Would you be interested in a patch that adds watchdog 
support for the built-in Zynq watchdog to u-boot?

Met vriendelijke groet / kind regards,

Mike Looijmans

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