linux-kernel - Re: [PATCH v3 3/4] watchdog: simatic-ipc-wdt: add new driver for Siemens Industrial PCs

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Date:   Mon, 12 Apr 2021 18:17:36 +0200
From:   Henning Schild <henning.schild@...mens.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        Srikanth Krishnakar <skrishnakar@...il.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Gerd Haeussler <gerd.haeussler.ext@...mens.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v3 3/4] watchdog: simatic-ipc-wdt: add new driver for
 Siemens Industrial PCs

Am Mon, 12 Apr 2021 09:06:10 -0700
schrieb Guenter Roeck <linux@...ck-us.net>:

> On 4/12/21 8:35 AM, Henning Schild wrote:
> > Am Thu, 1 Apr 2021 18:15:41 +0200
> > schrieb "Enrico Weigelt, metux IT consult" <lkml@...ux.net>:
> >   
> >> On 29.03.21 19:49, Henning Schild wrote:
> >>
> >> Hi,
> >>  
> >>> This driver adds initial support for several devices from Siemens.
> >>> It is based on a platform driver introduced in an earlier commit.
> >>>    
> >>
> >> Where does the wdt actually come from ?
> >>
> >> Is it in the SoC ? (which SoC exactly). SoC-builtin wdt is a
> >> pretty usual case.
> >>
> >> Or some external chip ?
> >>
> >> The code smells a bit like two entirely different wdt's that just
> >> have some similarities. If that's the case, I'd rather split it
> >> into two separate drivers and let the parent driver (board file)
> >> instantiate the correct one.  
> > 
> > In fact they are the same watchdog device. The only difference is
> > the "secondary enable" which controls whether the watchdog causes a
> > reboot or just raises an alarm. The alarm feature is not even
> > implemented in the given driver, we just enable that secondary
> > enable regardless. 
> 
> Confusing statement; I can't parse "we just enable that secondary
> enable regardless". What secondary enable do you enable ?
>
> The code says "set safe_en_n so we are not just WDIOF_ALARMONLY",
> which suggests that it disables the alarm feature, and does make
> sense.

Yes go with the second statement. But the alarm is the default after
boot, and turning it off needs to be done with p2sb gpio on the 427.
 
> > In one range of devices (227E) that second enable is part of a
> > pio-based control register. On the other range (427E) it
> > unfortunately is a P2SB gpio, which gets us right into the
> > discussion we have around the LEDs.
> > With that i have my doubts that two drivers would be the way to go,
> > most likely not. 
> >   
> 
> Reading the code again, I agree. Still, you'll need to sort out how
> to determine if the watchdog or the LED driver should be enabled,
> and how to access the gpio port. The GPIO pin detection and use
> for 427E is a bit awkward.

Yes it is awkward, and that is exactly the discussion happening for the
LEDs. Using generic GPIO code, the mail was more to Andy as i am hoping
he might help me connect the dots here. On the other hand i wanted wdt
discussions in the wdt thread, and not talk about that one gpio-pin in
the LED thread.

regards,
Henning

> Thanks,
> Guenter
> 
> > Only that i have no clue which pinctrl driver should be used here.
> > My guess is "sunrisepoint" because the CPUs are "SkyLake" i.e.
> > i5-6442EQ, i3-6102E
> > And "grep INT344B /sys/firmware/acpi/tables/DSDT" matches. I booted
> > a kernel patched with the series from Andy but the
> > "pinctrl-sunrisepoint" does not seem to even claim the memory.
> > Still trying to understand how to make use of these pinctrl drivers
> > they are in place but i lack example users (drivers). If they
> > should be available in sysfs, i might be looking at the wrong place
> > ... /sys/class/gpio/ does not list anything
> > 
> > regards,
> > Henning
> > 
> > 
> >   
> >>
> >> --mtx
> >>  
> >   
>