linux-kernel - Re: [PATCH v7] platform/chrome: cros_ec_lpc: Move host command to prepare/complete

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Message-ID: <CANkg5exCTrFVMidSnf1aB6mvwNSKXfFjE6P0NxZJHN0HC8qxGg@mail.gmail.com>
Date:   Thu, 1 Sep 2022 09:50:56 -0600
From:   Tim Van Patten <timvp@...gle.com>
To:     Tzung-Bi Shih <tzungbi@...nel.org>
Cc:     Raul Rangel <rrangel@...omium.org>,
        Rob Barnes <robbarnes@...gle.com>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        chrome-platform@...ts.linux.dev,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7] platform/chrome: cros_ec_lpc: Move host command to prepare/complete

On Wed, Aug 31, 2022 at 8:44 PM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
>
> On Wed, Aug 31, 2022 at 08:21:23PM -0600, Raul Rangel wrote:
> > On Wed, Aug 31, 2022 at 7:52 PM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
> > > > On Tue, Aug 23, 2022 at 9:59 AM Tim Van Patten <timvp@...gle.com> wrote:
> > > > >
> > > > > Update cros_ec_lpc_pm_ops to call cros_ec_lpc_prepare() during PM
> > > > > .prepare() and cros_ec_lpc_complete() during .complete(). This moves the
> > > > > host command that the AP sends and allows the EC to log entry/exit of
> > > > > AP's suspend/resume more accurately.
> > > > >
> > > > > Signed-off-by: Tim Van Patten <timvp@...gle.com>
> > > > > ---
> > > > >
> > > > > Changes in v7:
> > > > > - Rename "host event" to "host command" in title/description.
> > > > >
> > > > > Changes in v6:
> > > > > - Fully restore fixes from v3.
> > > > >
> > > > > Changes in v5:
> > > > > - Restore fixes from v3.
> > > > >
> > > > > Changes in v4:
> > > > > - Update title and description.
> > > > >
> > > > > Changes in v3:
> > > > > - Update cros_ec_lpc_suspend() to cros_ec_lpc_prepare()
> > > > > - Update cros_ec_lpc_resume() to cros_ec_lpc_complete()
> > > > >
> > > > > Changes in v2:
> > > > > - Include cros_ec_resume() return value in dev_info() output.
> > > > > - Guard setting .prepare/.complete with #ifdef CONFIG_PM_SLEEP.
> > >
> >
> > > I don't buy-in the ideas from the discussion in v3[1].  Thus, I would defer
> > > to other reviewers/maintainers on the list to seek their suggestions.
> > >
> > > [1]: https://patchwork.kernel.org/project/chrome-platform/patch/20220802113957.v3.1.I2c8c550183162e7594309b66d19af696b8d84552@changeid/
> >
> > Just to clarify, you are opposed to printing the return code because
> > `cros_ec_resume` currently always returns 0? Or is there another
> > objection?
>
> Yes.  I'm not sure if always printing 0 is a good idea.

We want the print statements to know when the EC sees suspend/resume
start/complete.   Having two versions of the same print statement, but
picking the correct one based on whether the return value is non-zero
is a bad design, which is why it always prints the return value.
Ignoring the return value entirely is also a bad design, since it can
change in the future. For example if cros_ec_resume() is updated to
pass along a bad return value instead of swallowing it always
returning 0.

-- 

Tim Van Patten | ChromeOS | timvp@...gle.com | (720) 432-0997