[U-Boot] Periodic task

[Heiko Schocher]

Hello Ran,

Am 26.08.2015 um 10:57 schrieb Ran Shalit:
> On Wed, Aug 26, 2015 at 10:05 AM, Heiko Schocher <hs at denx.de> wrote:
>> Hello Ran,
>>
>>
>> Am 26.08.2015 um 08:09 schrieb Ran Shalit:
>>>
>>> On Wed, Aug 26, 2015 at 7:45 AM, Heiko Schocher <hs at denx.de> wrote:
>>>>
>>>> Hello Ran,
>>>>
>>>> Am 25.08.2015 um 22:03 schrieb Ran Shalit:
>>>>>
>>>>>
>>>>> Hello,
>>>>>
>>>>> I need to do some periodic very simple task during u-boot prompt
>>>>> (while u-boot wais for commands). The task is very simple, just
>>>>> writing into a watchdog refresh register.
>>>>> But it seems that it's very difficult to "hack" u-boot with such
>>>>> periodic
>>>>> task.
>>>>> I see that main loop is waiting in loop for characters in a call to
>>>>> getc, which is a blocking command. If it was non-blocking, it might
>>>>> have help me. I'm not sure if there is a way to replace the getc with
>>>>> a non-blocking call.
>>>>>
>>>>> Does anyone have any idea if there is some simple way to do periodic
>>>>> task in u-boot  ?
>>>>
>>>>
>>>>
>>>> As you want to trigger a watchdog, have a look at
>>>> u-boot:/drivers/watchdog
>>>> and grep the U-Boot code for
>>>> CONFIG_WATCHDOG
>>>> CONFIG_HW_WATCHDOG
>>>>
>>>> bye,
>>>> Heiko
>>>> --
>>>
>>>
>>>
>>> Hi Heiko,
>>>
>>> That's a great suggestion.
>>> I can understand from this, that there is timer interrupt in the
>>> background for the watchdog refresh activity.
>>
>>
>> I do not know anything about your hw ... but timer interrupt is not
>> necessary.
>>
>> WATCHDOG_RESET is called from the U-Boot code ..
>> see definition in include/watchdog.h
>>
>>
>> bye,
>> Heiko
>> --
>
>
> Hi Heiko,
>
> I am using PPC mpc8349 freescale.
> In the arch/powerpc/lib/board.c file it does the following:
> ....
> for (;;) {
> WATCHDOG_RESET();
> main_loop();
> }
>
> There is something in the concept of u-boot flow that I don't uunderstand.
> How is it that main_loop will perdiocally return to WATCHDOG_RESET  if
> it waits for keyboard activity with getc() blocking function.

Look into the serial driver: drivers/serial/ns16550.c
NS16550_getc() triggers periodically the watchdog ...

bye,
Heiko
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