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Date:   Sat, 21 Jan 2023 17:58:11 +0000
From:   John Keeping <john@metanate.com>
To:     Sam Ravnborg <sam@ravnborg.org>
Cc:     Doug Anderson <dianders@chromium.org>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org,
        Stephen Boyd <swboyd@chromium.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Hsin-Yi Wang <hsinyi@chromium.org>
Subject: Re: [PATCH] drm/bridge: panel: Set orientation on panel_bridge
 connector
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References: <20230120114313.2087015-1-john@metanate.com>
 <CAD=FV=UPD6c+NY8Ub37N7LmrRFpcr6gKOh0Os14DaKrf3bKo2A@mail.gmail.com>
 <Y8uo7vIcQ6caH9pu@ravnborg.org>
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Hi Sam & Doug,

On Sat, Jan 21, 2023 at 09:57:18AM +0100, Sam Ravnborg wrote:
> On Fri, Jan 20, 2023 at 01:44:38PM -0800, Doug Anderson wrote:
> > On Fri, Jan 20, 2023 at 3:43 AM John Keeping <john@metanate.com> wrote:
> > >
> > > Commit 15b9ca1641f0 ("drm: Config orientation property if panel provides
> > > it") added a helper to set the panel panel orientation early but only
> > > connected this for drm_bridge_connector, which constructs a panel bridge
> > > with DRM_BRIDGE_ATTACH_NO_CONNECTOR and creates the connector itself.
> > >
> > > When the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not specified and the
> > > panel_bridge creates its own connector the orientation is not set unless
> > > the panel does it in .get_modes which is too late and leads to a warning
> > > splat from __drm_mode_object_add() because the device is already
> > > registered.
> > >
> > > Call the necessary function to set add the orientation property when the
> > > connector is created so that it is available before the device is
> > > registered.
> > 
> > I have no huge objection to your patch and it looks OK to me. That
> > being said, my understanding is that:
> > 
> > 1. DRM_BRIDGE_ATTACH_NO_CONNECTOR is "the future" and not using the
> > flag is "deprecated".
> Correct.
> Could we take a look at how much is required to move the relevant driver
> to use DRM_BRIDGE_ATTACH_NO_CONNECTOR?
>
> If this is too much work now we may land this simple patch, but the
> preference is to move all drivers to the new bridge handling and thus
> asking display drivers to create the connector.
> 
> What display driver are we dealing with here?

This is dw-mipi-dsi-rockchip which uses the component path in
dw-mipi-dsi (and, in fact, is the only driver using that mode of
dw-mipi-dsi).

I'm not familiar enough with DRM to say whether it's easy to convert to
DRM_BRIDGE_ATTACH_NO_CONNECTOR - should dw-mipi-dsi-rockchip be moving
to use dw-mipi-dsi as a bridge driver or should dw_mipi_dsi_bind() have
a drm_bridge_attach_flags argument?  But I'm happy to test patches if it
looks easy to convert to you :-)


John