linux-kernel - Re: [PATCH 4/4] drm/bridge: ti-sn65dsi86: Add NO

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Date:   Thu, 12 Aug 2021 13:08:11 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Rob Clark <robdclark@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Clark <robdclark@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] drm/bridge: ti-sn65dsi86: Add NO_CONNECTOR support

Laurent,

On Thu, Aug 12, 2021 at 12:26 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Rob,
>
> Thank you for the patch.
>
> On Wed, Aug 11, 2021 at 04:52:50PM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > Slightly awkward to fish out the display_info when we aren't creating
> > own connector.  But I don't see an obvious better way.
>
> We need a bit more than this, to support the NO_CONNECTOR case, the
> bridge has to implement a few extra operations, and set the bridge .ops
> field. I've submitted two patches to do so a while ago:
>
> - [RFC PATCH 08/11] drm/bridge: ti-sn65dsi86: Implement bridge connector operations ([1])

Rob asked me about this over IRC, so if he left it out and it's needed
then it's my fault. However, I don't believe it's needed until your
series making this bridge chip support full DP. For the the eDP case
the bridge chip driver in ToT no longer queries the EDID itself. It
simply provides an AUX bus to the panel driver and the panel driver
queries the EDID. I think that means we don't need to add
DRM_BRIDGE_OP_EDID, right?

I was also wondering if in the full DP case we should actually model
the physical DP jack as a drm_bridge and have it work the same way. It
would get probed via the DP AUX bus just like a panel. I seem to
remember Stephen Boyd was talking about modeling the DP connector as a
drm_bridge because it would allow us to handle the fact that some TCPC
chips could only support HBR2 whereas others could support HBR3. Maybe
it would end up being a fairly elegant solution?

> - [RFC PATCH 09/11] drm/bridge: ti-sn65dsi86: Make connector creation optional ([2])
>
> The second patch is similar to the first half of this patch, but misses
> the cleanup code. I'll try to rebase this and resubmit, but it may take
> a bit of time.

Whoops! You're right that Rob's patch won't work at all because we'll
just hit the "Fix bridge driver to make connector optional!" case. I
should have noticed that. :(

-Doug