[Automated-testing] power-control standard (was RE: Linaro Connect Report)

[Geert Uytterhoeven]

Hi Tim,

On Thu, Apr 11, 2019 at 8:25 PM <Tim.Bird at sony.com> wrote:
> > -----Original Message-----
> > From: Matt Hart
> >
> > On Thu, 11 Apr 2019 at 15:08, Dave Pigott <dave.pigott at linaro.org> wrote:
> > >
> > >
> > > > On 11 Apr 2019, at 01:51, <daniel.sangorrin at toshiba.co.jp>
> > <daniel.sangorrin at toshiba.co.jp> wrote:
> > > >
> > > > Thanks for the report Dan!
> > > >
> > > >> From: Dan Rue
> > > > [...]
> > > >> - Core pdu api actions: on, off, status
> > > >> - Core relay api actions: on, off, ???
> > > >
> > > > I think that we also talked about "reset" (or "reboot", but I think that
> > "reset" is a better verb because it implies that the operation is _forced_
> > unlike "reboot" which is usually done by the OS).
> > > > I am not an expert about PDUs/Relays but it seems that "reset" can be
> > realized by combining the "on" and "off" (experts, please correct me if I am
> > wrong) operations. That should work if the driver knows the limitations of
> > the PDU and can add the necessary delays. In that case, I guess we can safely
> > leave out the "reset" operation.
>
> Just to put in my 2 cents about the verb name.
>
> ttc uses 'reset' to mean a board reset - which sometimes corresponds to
> the Linux software 'reboot' command, and no hardware/power intervention, and sometimes
> to correspond to toggling the hardware 'reset' button (or pin).  Note that for some boards
> the hardware reset button has a different effect than a power cycle would, which is
> why these operations are separate in ttc.  (For example, in some cases it may be
> possible to retrieve the kernel log messages from memory after a reset but not
> after a reboot.)
>
> ttc uses 'reboot' to mean a hardware power cycle, with associated
> re-loading of the kernel and rootfs.
>
> ttc reboot performs a composite operation, which means that
> 'ttc reboot' does the entire process of power cycle, firmware bootstrap,
> and kernel boot.  It would call out to a power-control layer for portions
> of the whole reboot operation.
>
> ttc uses the verbs 'on' and 'off' for power control.  And  'ttc status' is used for
> status of more than just power control.  'ttc status' reports 4 things:
>  1) power status
>  2) network status (is device pingable?)
>  3) operational status (can a command be executed on the board?)
>  4) reservation status (does a test or a user have the board reserved, and for how long?)
>
> See https://elinux.org/Ttc_Program_Usage_Guide (this is somewhat dated, unfortunately)
>
> The power status by 'ttc status' (and what it expects from subsidiary helper scripts and apps)
> is a single word from the set ('ON', 'OFF', 'UNKOWN')
> (exactly as spelled, and in all uppercase).
>
> Fuego internally uses the following functions:
>
> rootfs_reboot - for a software or distribution-initiated reboot (ie Linux 'reboot' command)
> board_control_reboot - for a hardware reboot (ie PDU power cycle)
>
> Fuego doesn't use the 'reset' terminology.
>
> I think I was lobbying for 'reboot' in the meeting, but on further thought I don't think
> that word is good, as most people associate that with the full bootup process
> and not just the power control aspect of it.
>
> One other option for a name for the operation of turning the power off and on again,
> might be 'cycle'.  I've seen that used in some documentation for PDUs.
> And it would not conflict with names used elsewhere in the board control stack.
> So: "power-control minnowboard1 cycle" would be the command for turning the
> power off and on again, to the board named minnowboard1.

Switching a board on/off, or resetting it, can be done at multiple levels:
  1. External power supply,
  2. Board ("accessory") power switch (may be toggle or momentary),
  3. Reset button (may be more than one, e.g. master and peripheral reset),
  4. /sbin/reboot,
  5. /sbin/poweroff.

Of course all 5 (or more) may behave differently, and thus should be tested.

I have several boards where the hardware manual clearly states that external
power must only be restored or cut while the power switch is in the off
position.
Obviously this is violated by all board farms that keep this switch in the
on position permanently, and control power on/off and reset by method #1...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds