linux-kernel - Re: [PATCH v2 02/34] component: Introduce the aggregate bus

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Message-ID: <CAE-0n50YqKr1nKy-4WaxsfuwPiJ5kZcf46t-U_4i-TpfXzOX1g@mail.gmail.com>
Date:   Thu, 7 Oct 2021 14:40:07 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH v2 02/34] component: Introduce the aggregate bus_type

Quoting Saravana Kannan (2021-10-06 20:07:11)
> On Wed, Oct 6, 2021 at 12:38 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > diff --git a/drivers/base/component.c b/drivers/base/component.c
> > index 0a41bbe14981..d99e99cabb99 100644
> > --- a/drivers/base/component.c
> > +++ b/drivers/base/component.c
[...]
> > +                       continue;
> > +
> > +               /* Matches put in component_del() */
> > +               get_device(&adev->dev);
> > +               c->link = device_link_add(&adev->dev, c->dev,
> > +                                         DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
>
> Remove the STATELESS flag and you'll get a bunch of other stuff done for free:

I tried that and it didn't work for me. The aggregate device never
probed and I was left with no display. Let me see if I can reproduce it
with logging to provide more details.

> 1. The aggregate device would get force unbound when the component
> devices unbind.
> 2. You don't need to explicitly keep track of and delete the link. If
> either of the devices get deleted, it'll get deleted automatically.
> 3. It will avoid useless probe attempts of the aggregate device before
> all the component devices are probed.
>

I don't think point 3 is happening right now. We only try to probe the
aggregate device once all components probe.