linux-kernel - Re: [PATCH v2 3/3] watchdog:rit_wdt: Add support for WDIOF

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Message-ID: <b0f31712-a20f-f5c9-5b49-7473ef5d8be7@siemens.com>
Date:   Wed, 12 Jul 2023 11:34:11 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     "Li, Hua Qian (DI FA CTR IPC CN PRC4)" <HuaQian.Li@...mens.com>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Cc:     "Su, Bao Cheng (DI FA CTR IPC CN PRC4)" <baocheng.su@...mens.com>,
        "kristo@...nel.org" <kristo@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "huaqianlee@...il.com" <huaqianlee@...il.com>,
        "nm@...com" <nm@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "vigneshr@...com" <vigneshr@...com>
Subject: Re: [PATCH v2 3/3] watchdog:rit_wdt: Add support for WDIOF_CARDRESET

On 12.07.23 08:05, Li, Hua Qian (DI FA CTR IPC CN PRC4) wrote:
> On Tue, 2023-07-11 at 22:01 -0700, Guenter Roeck wrote:
>> On a higher level, the entire code puzzles me. Obviously there
>> must be a means for the BIOS or ROMMON to write PON_REASON_SOF_NUM
>> into some memory area. That means the BIOS/ROMMON must be able
>> to detect that situation. Why not use the same code to detect this
>> in the driver without the complexity of passing it from BIOS/ROMMON
>> to driver in some random memory area ?
>>
> In TI AM65x cases, the hardware is not capable of issuing a reset on
> its own, and is not possible to record or detect the watchdog reset
> situation. So `k3-rit-wdt` firmware which runs in a mcu core was used
> to detect the watchdog interrupt and reset the Soc. Here I am trying to
> write the reason in this firmware when watchdog interrupt happens, and
> read it out in kernel.

See https://github.com/siemens/k3-rti-wdt/issues/1 for where this
started and where the firmware part comes into play.

I still wonder why we couldn't have had a nicer hardware watchdog
instead but this can't be changed anymore.

Jan

-- 
Siemens AG, Technology
Competence Center Embedded Linux