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Date:   Thu, 21 Sep 2023 21:33:03 -0700
From:   Zev Weiss <zev@bewilderbeest.net>
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Andrew Jeffery <andrew@codeconstruct.com.au>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        linux-watchdog@vger.kernel.org, linux-aspeed@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        openbmc@lists.ozlabs.org,
        Thomas =?iso-8859-1?Q?Wei=DFschuh?= <linux@weissschuh.net>,
        Eddie James <eajames@linux.ibm.com>,
        Ivan Mikhaylov <i.mikhaylov@yadro.com>
Subject: Re: [PATCH] watchdog: aspeed: Add sysfs attributes for reset mask
 bits
Message-ID: <06a2428d-e1f3-4ecd-bd42-f3e25ffdbced@hatter.bewilderbeest.net>
References: <20230922013542.29136-2-zev@bewilderbeest.net>
 <91be26169ebbddf3c05cd19626478246cb72a72a.camel@codeconstruct.com.au>
 <85ddf493-934f-75c4-7a3a-728289c1ee09@roeck-us.net>
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On Thu, Sep 21, 2023 at 09:24:40PM PDT, Guenter Roeck wrote:
>On 9/21/23 21:16, Andrew Jeffery wrote:
>>On Thu, 2023-09-21 at 18:35 -0700, Zev Weiss wrote:
>>>The AST2500 and AST2600 watchdog timers provide the ability to control
>>>which devices are reset by the watchdog timer via a reset mask
>>>resgister.  Previously the driver ignored that register, leaving
>>>whatever configuration it found at boot and offering no way of
>>>altering its settings.  Add a 'reset_ctrl' sysfs subdirectory with a
>>>file per bit so that userspace can determine which devices the reset
>>>is applied to.
>>>
>>>Note that not all bits in the hardware register are exposed -- in
>>>particular, the ARM CPU and SOC/misc reset bits are left hidden since
>>>clearing them can render the system unable to reboot.
>>>
>>>Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
>>>---
>>>
>>>I'm porting OpenBMC to a platform that requires that the LPC controller remain
>>>un-reset by a BMC reboot.  With this patch userspace can control the reset
>>>mask of the Aspeed watchdog timer, with a few bits remaining unexposed so as
>>>to prevent some almost-certainly undesirable situations.  If there are other
>>>bits that people feel shouldn't be exposed (or conversely if someone feels
>>>strongly that the "dangerous" bits _should_ be exposed) I can adjust
>>>accordingly.
>>
>>
>>Is there a reason this has to be managed by userspace? It sounds a lot
>>like a property of platform design, in which case exposing this feature
>>in the devicetree might be a better approach.
>>
>
>Same sentiment here.
>
>Guenter
>
>

Yes, and indeed the same thing occurred to me, too, though unfortunately 
not until just *after* I sent the patch...I'll rework it as a DT thing 
instead.

Thanks,
Zev