Re: Extending wdt-gpio to be used on non-of (no DT) platforms

[Hauke Mehrtens <hauke-5/S+JYg5SzeELgA04lAiVw@public.gmane.org>]

On 03/29/2014 01:29 PM, Alexander Shiyan wrote:
> Sat, 29 Mar 2014 12:54:40 +0100 от Rafał Miłecki <zajec5-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
>> Hi guys,
>>
>> I've noticed gpio_wdt was added to the kernel to support some devices
>> based on devicetree.
>> We used to have our own (not mainlined) gpio_wdt in OpenWrt project:
>> http://git.openwrt.org/?p=openwrt.git;a=blob;f=target/linux/generic/patches-3.10/990-gpio_wdt.patch;hb=HEAD
>>
>> The main difference is that the mainlined one uses OF, while OpenWrt's
>> one uses plain platform API (with struct gpio_wdt_platform_data).
>>
>> I wanted to bring a topic of mainlining OpenWrt's solution. We
>> definitely need that and at the same time our device(s) don't use OF /
>> DT.
>>
>> Do you think we should extend wdt-gpio to handle that? Or do you think
>> this driver is so small, it's not worth it and we should submit a
>> separated one?
>>
>> Apart from API being used, one other difference I see is OpenWrt
>> supports different values for "first tick" and "interval". But that
>> could be easily handled.
> 
> In fact, this driver can be extended to non-DT support without adding
> any platform_data headers. This can be implemented by convert driver
> to using descriptor-based GPIO functions (gpiod_{}).
> HW timeout value in this case can be taken with module_param().

The Huawei E970, the only device with a bcm47xx SoC which uses this gpio
watchdog I know of, needs the gpio driver very early. It is not possible
to deactivate the watchdogs, so it has to get trigged very early in the
boot process. Module load time is too late. I think wdt-gpio should be
extended to support the old platform device interface with a own
platform_data header.

I added Mathias Adam, the author of the patch in OpenWrt.

Hauke
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