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 09:06:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Henning Schild <henning.schild@...mens.com>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     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

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.

> 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.

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
>>
>