linux-kernel - Re: [PATCH] component: Move host device to end of device lists on binding

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Message-ID: <CAJZ5v0h42fTKueFxrB6fpc9YBVNyDsCBryAf_geS-=0+OQQqjg@mail.gmail.com>
Date:   Tue, 11 May 2021 12:52:06 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Rob Clark <robdclark@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] component: Move host device to end of device lists on binding

On Mon, May 10, 2021 at 9:08 PM Stephen Boyd <swboyd@...omium.org> wrote:

[cut]

>
> >
> > > I will try it, but then I wonder about things like system wide
> > > suspend/resume too. The drm encoder chain would need to reimplement the
> > > logic for system wide suspend/resume so that any PM ops attached to the
> > > msm device run in the correct order. Right now the bridge PM ops will
> > > run, the i2c bus PM ops will run, and then the msm PM ops will run.
> > > After this change, the msm PM ops will run, the bridge PM ops will run,
> > > and then the i2c bus PM ops will run. It feels like that could be a
> > > problem if we're suspending the DSI encoder while the bridge is still
> > > active.
> >
> > Yup suspend/resume has the exact same problem as shutdown.
>
> I think suspend/resume has the exact opposite problem. At least I think
> the correct order is to suspend the bridge, then the encoder, i.e. DSI,
> like is happening today. It looks like drm_atomic_helper_shutdown()
> operates from the top down when we want bottom up? I admit I have no
> idea what is supposed to happen here.

Why would the system-wide suspend ordering be different from the
shutdown ordering?