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Date:   Wed, 12 Jul 2023 11:34:11 +0200
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Subject: Re: [PATCH v2 3/3] watchdog:rit_wdt: Add support for WDIOF_CARDRESET
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To:     "Li, Hua Qian (DI FA CTR IPC CN PRC4)" <HuaQian.Li@siemens.com>,
        "linux@roeck-us.net" <linux@roeck-us.net>,
        "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
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Cc:     "Su, Bao Cheng (DI FA CTR IPC CN PRC4)" <baocheng.su@siemens.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "huaqianlee@gmail.com" <huaqianlee@gmail.com>,
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From:   Jan Kiszka <jan.kiszka@siemens.com>
In-Reply-To: <42d578c52a590f50f90e2378ef3e2a1522038fc2.camel@siemens.com>
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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