linux-kernel - Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of drm_bridge_chain_pre

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Message-ID: <CAD=FV=UhqCe1r1kqVdmYOmy75j_v73RSjP0d0MX0q5zq2GVJoQ@mail.gmail.com>
Date:   Thu, 15 Apr 2021 07:48:25 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus W <linus.walleij@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Steev Klimaszewski <steev@...i.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of drm_bridge_chain_pre_enable()

Hi,

On Wed, Apr 14, 2021 at 6:56 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Doug,
>
> On Wed, Apr 14, 2021 at 06:19:13PM -0700, Doug Anderson wrote:
> > On Sun, Apr 4, 2021 at 5:50 PM Laurent Pinchart wrote:
> > > On Fri, Apr 02, 2021 at 03:28:35PM -0700, Douglas Anderson wrote:
> > > > The drm_bridge_chain_pre_enable() is not the proper opposite of
> > > > drm_bridge_chain_post_disable(). It continues along the chain to
> > > > _before_ the starting bridge. Let's fix that.
> > > >
> > > > Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
> > > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > > > Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> > > > ---
> > > >
> > > > (no changes since v1)
> > > >
> > > >  drivers/gpu/drm/drm_bridge.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > > > index 64f0effb52ac..044acd07c153 100644
> > > > --- a/drivers/gpu/drm/drm_bridge.c
> > > > +++ b/drivers/gpu/drm/drm_bridge.c
> > > > @@ -522,6 +522,9 @@ void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
> > > >       list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
> > > >               if (iter->funcs->pre_enable)
> > > >                       iter->funcs->pre_enable(iter);
> > > > +
> > > > +             if (iter == bridge)
> > > > +                     break;
> > >
> > > This looks good as it matches drm_atomic_bridge_chain_disable().
> > >
> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> >
> > Thanks for your review here and several of the other patches. Can you
> > suggest any plan for getting them landed? It would at least be nice to
> > get the non-controversial ones landed.
>
> Do you have commit access to drm-misc ? If not, given your
> contributions, I think you qualify for it.

No, I don't have access. I searched for how to get it and read through
the qualifications and, you're right, I think I do. I've hopefully
followed the right flow and created an issue to give me ssh access:

https://gitlab.freedesktop.org/freedesktop/freedesktop/-/issues/348

Is that something you (or someone else on this CC list) approves?


> > > I'm curious though, given that the bridge passed to the function should
> > > be the one closest to the encoder, does this make a difference ?
> >
> > Yes, that's how I discovered it originally. Let's see. So if I don't
> > have this patch but have the rest of the series then I get a splat at
> > bootup. This shows that dsi_mgr_bridge_pre_enable() must be "earlier"
> > in the chain than my bridge chip. Here's the splat:
>
> Right, I think it's caused by a later patch in the series calling this
> function with a different bridge than the one closest to the encoder.

Yup! I still wanted this patch to be first in the series, though,
since it's a bugfix that we'd want to land even if the later patches
changed in some way.

-Doug