linux-kernel - RE: [PATCH 0/2] rtc: pch-rtc: add Intel Series PCH built-in read-only RTC

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Message-ID: <OFBF96A764.75CCED3A-ON00258734.0062B30C-00258734.00634222@ibm.com>
Date:   Tue, 17 Aug 2021 18:04:09 +0000
From:   "Milton Miller II" <miltonm@...ibm.com>
To:     "Alexandre Belloni" <alexandre.belloni@...tlin.com>
Cc:     "Paul Fertser" <fercerpav@...il.com>,
        "Ivan Mikhaylov" <i.mikhaylov@...ro.com>,
        "Alessandro Zummo" <a.zummo@...ertech.it>,
        openbmc@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: RE: [PATCH 0/2] rtc: pch-rtc: add Intel Series PCH built-in read-only RTC


On Aug 16, 2021, Alexandre Belloni wrote:
>On 15/08/2021 01:42:15+0300, Paul Fertser wrote:
>> On Tue, Aug 10, 2021 at 06:44:34PM +0300, Ivan Mikhaylov wrote:
>> > Add RTC driver with dt binding tree document. Also this driver
>adds one sysfs
>> > attribute for host power control which I think is odd for RTC
>driver.
>> > Need I cut it off and use I2C_SLAVE_FORCE? I2C_SLAVE_FORCE is not
>good
>> > way too from my point of view. Is there any better approach?
>> 
>> Reading the C620 datasheet I see this interface also allows other
>> commands (wake up, watchdog feeding, reboot etc.) and reading
>statuses
>> (e.g Intruder Detect, POWER_OK_BAD).
>> 
>> I think if there's any plan to use anything other but RTC via this
>> interface then the driver should be registered as an MFD.
>> 
>
>This is not the current thinking, if everything is integrated, then
>there is no issue registering a watchdog from the RTC driver. I'll
>let
>you check with Lee...

I think the current statement is "if they are truly disjoint 
hardware controls" then an MFD might suffice, but if they require 
software cordination the new auxillary bus seems to be desired.

>>However, I'm not sure what is the correct interface for
>poweroff/reboot
>control.

While there is a gpio interface to a simple regulator switch,
the project to date has been asserting direct or indirect 
gpios etc to control the host.   If these are events to 
trigger a change in state and not a direct state change
that some controller trys to follow, maybe a message delivery 
model?   (this is not to reboot or cycle the bmc).

milton