linux-kernel - Re: [PATCH] drivers/cros

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Message-ID: <CA+Dqm33CAjWv=DFhp0+iee2-EugJzjWOYcyfieaULq2H9egheA@mail.gmail.com>
Date:   Tue, 3 Jan 2023 16:14:59 -0700
From:   Rob Barnes <robbarnes@...gle.com>
To:     Prashant Malani <pmalani@...omium.org>
Cc:     Guenter Roeck <groeck@...omium.org>,
        chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org,
        dtor@...omium.org, Benson Leung <bleung@...omium.org>
Subject: Re: [PATCH] drivers/cros_ec: Handle CrOS EC panics

On Wed, Dec 21, 2022 at 5:38 PM Prashant Malani <pmalani@...omium.org> wrote:
>
> On Wed, Dec 21, 2022 at 3:55 PM Rob Barnes <robbarnes@...gle.com> wrote:
> >
> > On Wed, Dec 21, 2022 at 12:23 PM Prashant Malani <pmalani@...omium.org> wrote:
> > >
> > >
> > > Can you provide a link (either in the commit, or here in the comment)
> > > to the coreboot/BIOS code which uses this value? I feel this should
> > > be documented in some form that correlates the caller and the callee.
> >
> > Link: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/+/4023535
>
> Thanks. Please add a code link (for example, I could find [2], but you
> could use another code mirror
> if there is a canonical one for coreboot) to the commit description,
> or in the comment when you send
> out v2.
>
> > > Any reason we cannot use the existing event_notifier (with value argument)?
> > > It's a system panic, so I doubt that computational overhead for other
> > > notifier block
> > > listeners is a concern.
> >
> > The value field is already being used for "queued_during_suspend" in
> > event_notifier.
>
> OK, I suppose you could use the data pointer...

The data pointer contains ec_dev, so that's not really an option either.

>
> It's just I find having a notifier for a single use case overkill(even
> 2 would be fine); one could get away with exposing a method
> in cros_typec_debugfs via a local .h file (it can compile to a stub if
> cros_typec_debugfs is not compiled to the kernel);
> the LPC code can then just call that method instead of invoking a notifier.

My first implementation did make a direct call to cros_ec_debugfs.c,
but an internal reviewer recommended using an event notifier instead.
So I'm histent to go back to a direct call.

There may be other sub drivers that want to handle EC panics. So I
think keeping this as a separate notifier makes sense given the
constraints.

>
> Best regards,
>
> -Prashant
>
> > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144
> [2] https://github.com/coreboot/coreboot/blob/ff6b3af113f84a1957dcdf8a8179a751ce08becf/src/ec/google/chromeec/acpi/ec.asl#L15