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

[Mike Looijmans]

I wrote this a while ago:

> On 03/26/2014 10:26 AM, Mike Looijmans wrote:
>> 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.
...
>> Related question #1: Would you be interested in a patch that adds GPIO support for the Zynq to u-boot?

Now for something completely mysterious: I can no longer control GPIO from 
within u-boot.

I tested this before on another board with LED, and it worked just fine.

Now I cannot even read/write the GPIO registers from within u-boot, for 
example an attempt to enable the output mode of bank 0 for pin 15:

zynq-uboot> mw.l 0xE000A204 0x8000 2
zynq-uboot> md.l 0xE000A204 2
e000a204: 00000000 00000000                      ........
zynq-uboot> mw.l 0xE000A204 0x8000 2
zynq-uboot> md.l 0xE000A204 2
e000a204: 00000000 00000000                      ........
zynq-uboot>

Once the kernel is running, I can happily bitbang those registers and this 
works fine. It works on other boards too.
What can cause the GPIO registers to fail to work? I can't even read/write 
them? Maybe the GPIO clock somehow got disabled or so?

For example, on a zedboard I get this:

zynq-uboot> md.l 0xE000A204 2
e000a204: 00000000 00000000                      ........
zynq-uboot> mw.l 0xE000A204 0x8000 2
zynq-uboot> md.l 0xE000A204 2
e000a204: 00008000 00008000                      ........
zynq-uboot>

As you can see, the register values are neatly preserved.


Met vriendelijke groet / kind regards,

Mike Looijmans

TOPIC Embedded Systems
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