[Letux-kernel] Palmas wtchdog driver?

H. Nikolaus Schaller hns at goldelico.com
Sat Dec 15 10:22:20 CET 2018


Hi Graeme,

> Am 15.12.2018 um 10:01 schrieb Graeme Gregory <gg at slimlogic.co.uk>:
> 
> 
> 
> On Sat, 15 Dec 2018, at 7:50 AM, H. Nikolaus Schaller wrote:
>> Hi Tony,
>> 
>>> Am 13.12.2018 um 19:14 schrieb Tony Lindgren <tony at atomide.com>:
>>> 
>>> * H. Nikolaus Schaller <hns at goldelico.com> [181208 21:35]:
>>>> Hi Tony,
>>>> I had the OMAP5 running very very hot by a kernel hang (most likely a spinlock).
>>>> And I wondered if there is no safety mechanism (watchdog timer).
>>>> 
>>>> I did a little research and there seems to be no WDT driver for the Palmas in
>>>> mainline.
>>>> 
>>>> There was something:
>>>> 
>>>> 	https://lore.kernel.org/patchwork/patch/367777/
>>>> 
>>>> but it seems it did not arrive upstream.
>>>> Any reasons or problems with the driver? Or a newer version sitting in some
>>>> git?
>>> 
>>> Sorry no idea. Maybe check if it's similar to the
>>> drivers/watchdog/twl4030_wdt.c?
>> 
>> Yes, it is. Code structure is almost the same, because it is based on 
>> twl4030 code :)
>> 
>> Differences:
>> * uses enable/disable instead of start/stop (probably older WDT core API 
>> and easy to fix)
>> * different compatible list (obviously necessary)
>> * uses palmas_write() from include/linux/mfd/palmas.h instead of 
>> twl_i2c_write_u8() from include/linux/mfd/twl.h
>> * (have not checked): probably different register offsets
>> * has no remove/suspend/resume handlers (probably older WDT core API and 
>> easy to copy&paste)
>> 
>> But there seems to be a bug in palmas_wdt_write(). IMHO it ignores the "data"
>> argument when passing down to palmas_write()...
>> 
>> So it may be that the driver did not work as proposed.
>> 
>> I am not sure but I think I had spotted a v10 of the patch set.
>> 
>> Ah, yes:
>> 
>> 	https://lore.kernel.org/patchwork/patch/367819/
>> 
>> There are already several review comments (including confirmation of
>> the data argument issue) but I could not find a v11 or v12.
>> 
>>> 
>>> Note that some devices just use drivers/watchdog/omap_wdt.c
>>> that is wired to the PMIC used. So maybe the Palmas WDT
>>> was just forgotten if it was not needed?
>> 
>> Maybe it was simply forgotten to be completed and resubmitted.
>> 
>> I am not sure if Graeme is still actively working on this
>> topic. So I put him on CC.
>> 
> TImageddon ended my access to the documentation on that chip as I was contracted for it. I never saw the actual release version of the chip :-(

Ok, I see...

Well, we hope the Pyra handheld will go to mass production soon.
And IMHO the Palmas documentations are now available officially somewhere.

Anyways, I have pulled your patch and hope that I can make it working in the
next weeks. I would be happy if you could participate in review when I try
to get it upstream.

BR and thanks,
Nikolaus



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