Re: [PATCH] watchdog: aspeed: Add sysfs attributes for reset mask bits

[Zev Weiss <zev@bewilderbeest.net>]

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