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Message-ID: <teokrp5lycipuchh6e64tvqabxzzf4ez7epuyrae5ahd7dqnjs@x7vyrjgzth2i>
Date: Fri, 14 Feb 2025 02:32:56 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Rob Clark <robdclark@...il.com>,
Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>,
Marijn Suijten <marijn.suijten@...ainline.org>, Hermes Wu <Hermes.wu@....com.tw>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v2 1/3] drm/display: bridge-connector: add DisplayPort
bridges
On Fri, Feb 14, 2025 at 01:57:45AM +0200, Laurent Pinchart wrote:
> Hi Dmitry,
>
> Thank you for the patch.
>
> On Sun, Feb 09, 2025 at 03:41:18PM +0200, Dmitry Baryshkov wrote:
> > DRM HDMI Codec framework is useful not only for the HDMI bridges, but
> > also for the DisplayPort bridges. Add new DRM_BRIDGE_OP_DisplayPort
> > define in order to distinguish DP bridges. Create HDMI codec device
> > automatically for DP bridges which have declared audio support.
> >
> > Note, unlike HDMI devices, which already have a framework to handle HPD
> > notifications in a standard way, DP drivers don't (yet?) have such a
> > framework. As such it is necessary to manually call
> > drm_connector_hdmi_audio_plugged_notify(). This requirement hopefully
> > can be lifted later on, if/when DRM framework gets better DisplayPort
> > ports support in the core layer.
> >
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> > drivers/gpu/drm/display/drm_bridge_connector.c | 66 ++++++++++++++++++++------
> > include/drm/drm_bridge.h | 14 +++++-
> > 2 files changed, 65 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
> > index 30c736fc0067e31a97db242e5b16ea8a5b4cf359..5e031395b801f9a1371dcb4ac09f3da23e4615dd 100644
> > --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
> > @@ -98,6 +98,13 @@ struct drm_bridge_connector {
> > * HDMI connector infrastructure, if any (see &DRM_BRIDGE_OP_HDMI).
> > */
> > struct drm_bridge *bridge_hdmi;
> > + /**
> > + * @bridge_dp:
> > + *
> > + * The bridge in the chain that implements necessary support for the
> > + * DisplayPort connector infrastructure, if any (see &DRM_BRIDGE_OP_DisplayPort).
> > + */
> > + struct drm_bridge *bridge_dp;
> > };
> >
> > #define to_drm_bridge_connector(x) \
> > @@ -496,6 +503,25 @@ static const struct drm_connector_hdmi_audio_funcs drm_bridge_connector_hdmi_aud
> > .mute_stream = drm_bridge_connector_audio_mute_stream,
> > };
> >
> > +static int drm_bridge_connector_hdmi_audio_init(struct drm_connector *connector,
> > + struct drm_bridge *bridge)
> > +{
> > + if (!bridge->hdmi_audio_max_i2s_playback_channels &&
> > + !bridge->hdmi_audio_spdif_playback)
> > + return 0;
> > +
> > + if (!bridge->funcs->hdmi_audio_prepare ||
> > + !bridge->funcs->hdmi_audio_shutdown)
> > + return -EINVAL;
> > +
> > + return drm_connector_hdmi_audio_init(connector,
> > + bridge->hdmi_audio_dev,
> > + &drm_bridge_connector_hdmi_audio_funcs,
> > + bridge->hdmi_audio_max_i2s_playback_channels,
> > + bridge->hdmi_audio_spdif_playback,
> > + bridge->hdmi_audio_dai_port);
> > +}
> > +
> > /* -----------------------------------------------------------------------------
> > * Bridge Connector Initialisation
> > */
> > @@ -564,6 +590,8 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > if (bridge->ops & DRM_BRIDGE_OP_HDMI) {
> > if (bridge_connector->bridge_hdmi)
> > return ERR_PTR(-EBUSY);
> > + if (bridge_connector->bridge_dp)
> > + return ERR_PTR(-EINVAL);
> > if (!bridge->funcs->hdmi_write_infoframe ||
> > !bridge->funcs->hdmi_clear_infoframe)
> > return ERR_PTR(-EINVAL);
> > @@ -576,6 +604,16 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > max_bpc = bridge->max_bpc;
> > }
> >
> > + if (bridge->ops & DRM_BRIDGE_OP_DisplayPort) {
> > + if (bridge_connector->bridge_dp)
> > + return ERR_PTR(-EBUSY);
> > + if (bridge_connector->bridge_hdmi)
> > + return ERR_PTR(-EINVAL);
> > +
> > + bridge_connector->bridge_dp = bridge;
> > +
> > + }
> > +
> > if (!drm_bridge_get_next_bridge(bridge))
> > connector_type = bridge->type;
> >
> > @@ -612,21 +650,21 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > if (ret)
> > return ERR_PTR(ret);
> >
> > - if (bridge->hdmi_audio_max_i2s_playback_channels ||
> > - bridge->hdmi_audio_spdif_playback) {
> > - if (!bridge->funcs->hdmi_audio_prepare ||
> > - !bridge->funcs->hdmi_audio_shutdown)
> > - return ERR_PTR(-EINVAL);
> > + ret = drm_bridge_connector_hdmi_audio_init(connector, bridge);
> > + if (ret)
> > + return ERR_PTR(ret);
> > + } else if (bridge_connector->bridge_dp) {
> > + bridge = bridge_connector->bridge_dp;
> >
> > - ret = drm_connector_hdmi_audio_init(connector,
> > - bridge->hdmi_audio_dev,
> > - &drm_bridge_connector_hdmi_audio_funcs,
> > - bridge->hdmi_audio_max_i2s_playback_channels,
> > - bridge->hdmi_audio_spdif_playback,
> > - bridge->hdmi_audio_dai_port);
> > - if (ret)
> > - return ERR_PTR(ret);
> > - }
> > + ret = drmm_connector_init(drm, connector,
> > + &drm_bridge_connector_funcs,
> > + connector_type, ddc);
> > + if (ret)
> > + return ERR_PTR(ret);
> > +
> > + ret = drm_bridge_connector_hdmi_audio_init(connector, bridge);
> > + if (ret)
> > + return ERR_PTR(ret);
> > } else {
> > ret = drmm_connector_init(drm, connector,
> > &drm_bridge_connector_funcs,
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index 496dbbd2ad7edff7f091adfbe62de1e33ef0cf07..40f37444426b1b8ded25da9ba9e2963f18ad6267 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -811,9 +811,21 @@ enum drm_bridge_ops {
> > *
> > * Note: currently there can be at most one bridge in a chain that sets
> > * this bit. This is to simplify corresponding glue code in connector
> > - * drivers.
> > + * drivers. Having both HDMI and DisplayPort bridges in the same bridge
> > + * chain is also not allowed.
> > */
> > DRM_BRIDGE_OP_HDMI = BIT(4),
> > + /**
> > + * @DRM_BRIDGE_OP_DisplayPort: The bridge provides DisplayPort connector
> > + * operations. Currently this is limited to the optional HDMI codec
> > + * support.
> > + *
> > + * Note: currently there can be at most one bridge in a chain that sets
> > + * this bit. This is to simplify corresponding glue code in connector
> > + * drivers. Having both HDMI and DisplayPort bridges in the same bridge
> > + * chain is also not allowed.
> > + */
> > + DRM_BRIDGE_OP_DisplayPort = BIT(5),
>
> The OP bits are not supposed to describe tbe type of bridge, but the
> operations it implements. I see quite a bit of duplication between HDMI
> and DisplayPort in this patch. Can we have a single bit named after the
> feature that you want to support ? The bridge_hdmi and bridge_dp fields
> should also be merged into a single one.
In this case these ops actually describe the set of ops implemented by
the bridge. DRM_BRIDGE_OP_HDMI implements hdmi_tmds_char_rate_valid(),
hdmi_write_infoframe(), hdmi_clear_infoframe() and hdmi_audio_*()
callbacks. It is impossible to just use HDMI helpers for any
DRM_MODE_CONNECTOR_HDMIA bridge as they lack required callbacks.
At the same time it is perfectly legic to have a
DRM_MODE_CONNECTOR_HDMIA bridge which doesn't set DRM_BRIDGE_OP_HDMI:
this bridge chain will not use HDMI Connector / HDMI State helpers, but
it should be fine otherwise.
DRM_BRIDGE_OP_DisplayPort bridges currently implement hdmi_audio_*(),
but I have long-term plans for that set of ops.
It is not quite possible to merge bridge_hdmi and bridge_dp fields:
for bridges, which implement DRM_BRIDGE_OP_HDMI, drm_bridge_connector
call various drm_atomic_helper_connector_hdmi_*() functions. For
DisplayPort there is no corresponding functionality (yet).
--
With best wishes
Dmitry
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