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SubjectRe: [PATCH 1/2] drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.
Date
Hi Archit,

On Wednesday 03 May 2017 14:53:00 Archit Taneja wrote:
> On 04/27/2017 10:06 PM, Eric Anholt wrote:
> > Many DRM drivers have common code to make a stub connector
> > implementation that wraps a drm_panel. By wrapping the panel in a DRM
> > bridge, all of the connector code (including calls during encoder
> > enable/disable) goes away.
> >
> > Signed-off-by: Eric Anholt <eric@anholt.net>
> > ---
> >
> > Documentation/gpu/drm-kms-helpers.rst | 3 +
> > drivers/gpu/drm/bridge/Kconfig | 11 +-
> > drivers/gpu/drm/bridge/Makefile | 1 +
> > drivers/gpu/drm/bridge/lvds-encoder.c | 158 ++++------------------------
> > drivers/gpu/drm/bridge/panel.c | 188 +++++++++++++++++++++++++++++
> > include/drm/drm_bridge.h | 8 ++
> > 6 files changed, 228 insertions(+), 141 deletions(-)
> > create mode 100644 drivers/gpu/drm/bridge/panel.c
> >
> > diff --git a/Documentation/gpu/drm-kms-helpers.rst
> > b/Documentation/gpu/drm-kms-helpers.rst index c075aadd7078..60eb3b41702b
> > 100644
> > --- a/Documentation/gpu/drm-kms-helpers.rst
> > +++ b/Documentation/gpu/drm-kms-helpers.rst
> > @@ -143,6 +143,9 @@ Bridge Helper Reference
> > .. kernel-doc:: drivers/gpu/drm/drm_bridge.c
> > :export:
> >
> > +.. kernel-doc:: drivers/gpu/drm/bridge/panel.c
> > + :export:
> > +
> > .. _drm_panel_helper:
> > Panel Helper Reference
> >
> > diff --git a/drivers/gpu/drm/bridge/Kconfig
> > b/drivers/gpu/drm/bridge/Kconfig index f6968d3b4b41..c4daca38743c 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -4,6 +4,14 @@ config DRM_BRIDGE
> > help
> > Bridge registration and lookup framework.
> >
> > +config DRM_PANEL_BRIDGE
> > + def_bool y
> > + depends on DRM_BRIDGE
> > + select DRM_KMS_HELPER
> > + select DRM_PANEL
> > + help
> > + DRM bridge wrapper of DRM panels
> > +
> > menu "Display Interface Bridges"
> > depends on DRM && DRM_BRIDGE
> >
> > @@ -27,8 +35,7 @@ config DRM_DUMB_VGA_DAC
> > config DRM_LVDS_ENCODER
> > tristate "Transparent parallel to LVDS encoder support"
> > depends on OF
> > - select DRM_KMS_HELPER
> > - select DRM_PANEL
> > + select DRM_PANEL_BRIDGE
> > help
> > Support for transparent parallel to LVDS encoders that don't require
> > any configuration.
> > diff --git a/drivers/gpu/drm/bridge/Makefile
> > b/drivers/gpu/drm/bridge/Makefile index 3fe2226ee2f2..40a43750ad55 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -5,6 +5,7 @@ obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
> > obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
> > obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) +=
> > megachips-stdpxxxx-ge-b850v3-fw.o obj-$(CONFIG_DRM_NXP_PTN3460) +=
> > nxp-ptn3460.o
> > +obj-$(CONFIG_DRM_PANEL_BRIDGE) += panel.o
> > obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> > obj-$(CONFIG_DRM_SIL_SII8620) += sil-sii8620.o
> > obj-$(CONFIG_DRM_SII902X) += sii902x.o
> > diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c
> > b/drivers/gpu/drm/bridge/lvds-encoder.c index f1f67a279426..04e1504c4d8f
> > 100644
> > --- a/drivers/gpu/drm/bridge/lvds-encoder.c
> > +++ b/drivers/gpu/drm/bridge/lvds-encoder.c
> > @@ -8,144 +8,18 @@
> > */
> >
> > #include <drm/drmP.h>
> > -#include <drm/drm_atomic_helper.h>
> > -#include <drm/drm_connector.h>
> > -#include <drm/drm_crtc_helper.h>
> > -#include <drm/drm_encoder.h>
> > -#include <drm/drm_modeset_helper_vtables.h>
> > +#include <drm/drm_bridge.h>
> > #include <drm/drm_panel.h>
> >
> > #include <linux/of_graph.h>
> >
> > -struct lvds_encoder {
> > - struct device *dev;
> > -
> > - struct drm_bridge bridge;
> > - struct drm_connector connector;
> > - struct drm_panel *panel;
> > -};
> > -
> > -static inline struct lvds_encoder *
> > -drm_bridge_to_lvds_encoder(struct drm_bridge *bridge)
> > -{
> > - return container_of(bridge, struct lvds_encoder, bridge);
> > -}
> > -
> > -static inline struct lvds_encoder *
> > -drm_connector_to_lvds_encoder(struct drm_connector *connector)
> > -{
> > - return container_of(connector, struct lvds_encoder, connector);
> > -}
> > -
> > -static int lvds_connector_get_modes(struct drm_connector *connector)
> > -{
> > - struct lvds_encoder *lvds = drm_connector_to_lvds_encoder(connector);
> > -
> > - return drm_panel_get_modes(lvds->panel);
> > -}
> > -
> > -static const struct drm_connector_helper_funcs
> > lvds_connector_helper_funcs = { - .get_modes = lvds_connector_get_modes,
> > -};
> > -
> > -static const struct drm_connector_funcs lvds_connector_funcs = {
> > - .dpms = drm_atomic_helper_connector_dpms,
> > - .reset = drm_atomic_helper_connector_reset,
> > - .fill_modes = drm_helper_probe_single_connector_modes,
> > - .destroy = drm_connector_cleanup,
> > - .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> > - .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > -};
> > -
> > -static int lvds_encoder_attach(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > - struct drm_connector *connector = &lvds->connector;
> > - int ret;
> > -
> > - if (!bridge->encoder) {
> > - DRM_ERROR("Missing encoder\n");
> > - return -ENODEV;
> > - }
> > -
> > - drm_connector_helper_add(connector, &lvds_connector_helper_funcs);
> > -
> > - ret = drm_connector_init(bridge->dev, connector,
&lvds_connector_funcs,
> > - DRM_MODE_CONNECTOR_LVDS);
> > - if (ret) {
> > - DRM_ERROR("Failed to initialize connector\n");
> > - return ret;
> > - }
> > -
> > - drm_mode_connector_attach_encoder(&lvds->connector, bridge->encoder);
> > -
> > - ret = drm_panel_attach(lvds->panel, &lvds->connector);
> > - if (ret < 0)
> > - return ret;
> > -
> > - return 0;
> > -}
> > -
> > -static void lvds_encoder_detach(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > -
> > - drm_panel_detach(lvds->panel);
> > -}
> > -
> > -static void lvds_encoder_pre_enable(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > -
> > - drm_panel_prepare(lvds->panel);
> > -}
> > -
> > -static void lvds_encoder_enable(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > -
> > - drm_panel_enable(lvds->panel);
> > -}
> > -
> > -static void lvds_encoder_disable(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > -
> > - drm_panel_disable(lvds->panel);
> > -}
> > -
> > -static void lvds_encoder_post_disable(struct drm_bridge *bridge)
> > -{
> > - struct lvds_encoder *lvds = drm_bridge_to_lvds_encoder(bridge);
> > -
> > - drm_panel_unprepare(lvds->panel);
> > -}
> > -
> > -static const struct drm_bridge_funcs lvds_encoder_bridge_funcs = {
> > - .attach = lvds_encoder_attach,
> > - .detach = lvds_encoder_detach,
> > - .pre_enable = lvds_encoder_pre_enable,
> > - .enable = lvds_encoder_enable,
> > - .disable = lvds_encoder_disable,
> > - .post_disable = lvds_encoder_post_disable,
> > -};
> > -
> >
> > static int lvds_encoder_probe(struct platform_device *pdev)
> > {
> >
> > - struct lvds_encoder *lvds;
> >
> > struct device_node *port;
> > struct device_node *endpoint;
> >
> > - struct device_node *panel;
> > -
> > - lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
> > - if (!lvds)
> > - return -ENOMEM;
> > -
> > - lvds->dev = &pdev->dev;
> > - platform_set_drvdata(pdev, lvds);
> > -
> > - lvds->bridge.funcs = &lvds_encoder_bridge_funcs;
> > - lvds->bridge.of_node = pdev->dev.of_node;
> > + struct device_node *panel_node;
> > + struct drm_panel *panel;
> > + struct drm_bridge *bridge;
> >
> > /* Locate the panel DT node. */
> > port = of_graph_get_port_by_id(pdev->dev.of_node, 1);
> >
> > @@ -161,29 +35,35 @@ static int lvds_encoder_probe(struct platform_device
> > *pdev)>
> > return -ENXIO;
> >
> > }
> >
> > - panel = of_graph_get_remote_port_parent(endpoint);
> > + panel_node = of_graph_get_remote_port_parent(endpoint);
> >
> > of_node_put(endpoint);
> >
> > - if (!panel) {
> > + if (!panel_node) {
> >
> > dev_dbg(&pdev->dev, "no remote endpoint for port 1\n");
> > return -ENXIO;
> >
> > }
> >
> > - lvds->panel = of_drm_find_panel(panel);
> > - of_node_put(panel);
> > - if (!lvds->panel) {
> > + panel = of_drm_find_panel(panel_node);
> > + of_node_put(panel_node);
> > + if (!panel) {
> >
> > dev_dbg(&pdev->dev, "panel not found, deferring probe\n");
> > return -EPROBE_DEFER;
> >
> > }
> >
> > - /* Register the bridge. */
> > - return drm_bridge_add(&lvds->bridge);
> > + bridge = drm_panel_bridge_add(&pdev->dev, panel,
> > + DRM_MODE_CONNECTOR_LVDS);
> > + if (IS_ERR(bridge))
> > + return PTR_ERR(bridge);
> > +
> > + platform_set_drvdata(pdev, bridge);
> > +
> > + return 0;
> >
> > }
> >
> > static int lvds_encoder_remove(struct platform_device *pdev)
> > {
> >
> > - struct lvds_encoder *encoder = platform_get_drvdata(pdev);
> > + struct drm_bridge *bridge = platform_get_drvdata(pdev);
> >
> > - drm_bridge_remove(&encoder->bridge);
> > + drm_bridge_remove(bridge);
> >
> > return 0;
> >
> > }
> >
> > diff --git a/drivers/gpu/drm/bridge/panel.c
> > b/drivers/gpu/drm/bridge/panel.c new file mode 100644
> > index 000000000000..2081245455c6
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/panel.c
> > @@ -0,0 +1,188 @@
> > +/*
> > + * Copyright (C) 2016 Laurent Pinchart
> > <laurent.pinchart@ideasonboard.com>
> > + * Copyright (C) 2017 Broadcom
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation; either version 2 of
> > + * the License, or (at your option) any later version.
> > + */
> > +
> > +#include <drm/drmP.h>
> > +#include <drm/drm_panel.h>
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_connector.h>
> > +#include <drm/drm_crtc_helper.h>
> > +#include <drm/drm_encoder.h>
> > +#include <drm/drm_modeset_helper_vtables.h>
> > +#include <drm/drm_panel.h>
> > +
> > +struct panel_bridge {
> > + struct drm_bridge bridge;
> > + struct device *dev;
> > + struct drm_connector connector;
> > + struct drm_panel *panel;
> > + u32 connector_type;
> > +};
> > +
> > +static inline struct panel_bridge *
> > +drm_bridge_to_panel_bridge(struct drm_bridge *bridge)
> > +{
> > + return container_of(bridge, struct panel_bridge, bridge);
> > +}
> > +
> > +static inline struct panel_bridge *
> > +drm_connector_to_panel_bridge(struct drm_connector *connector)
> > +{
> > + return container_of(connector, struct panel_bridge, connector);
> > +}
> > +
> > +static int panel_bridge_connector_get_modes(struct drm_connector
> > *connector) +{
> > + struct panel_bridge *panel_bridge =
> > + drm_connector_to_panel_bridge(connector);
> > +
> > + return drm_panel_get_modes(panel_bridge->panel);
> > +}
> > +
> > +static const struct drm_connector_helper_funcs
> > panel_bridge_connector_helper_funcs = { + .get_modes =
> > panel_bridge_connector_get_modes,
> > +};
> > +
> > +static const struct drm_connector_funcs panel_bridge_connector_funcs = {
> > + .dpms = drm_atomic_helper_connector_dpms,
> > + .reset = drm_atomic_helper_connector_reset,
> > + .fill_modes = drm_helper_probe_single_connector_modes,
> > + .destroy = drm_connector_cleanup,
> > + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> > + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > +};
> > +
> > +static int panel_bridge_attach(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > + struct drm_connector *connector = &panel_bridge->connector;
> > + int ret;
> > +
> > + if (!bridge->encoder) {
> > + DRM_ERROR("Missing encoder\n");
> > + return -ENODEV;
> > + }
> > +
> > + drm_connector_helper_add(connector,
> > + &panel_bridge_connector_helper_funcs);
> > +
> > + ret = drm_connector_init(bridge->dev, connector,
> > + &panel_bridge_connector_funcs,
> > + panel_bridge->connector_type);
> > + if (ret) {
> > + DRM_ERROR("Failed to initialize connector\n");
> > + return ret;
> > + }
> > +
> > + drm_mode_connector_attach_encoder(&panel_bridge->connector,
> > + bridge->encoder);
> > +
> > + ret = drm_panel_attach(panel_bridge->panel, &panel_bridge->connector);
> > + if (ret < 0)
> > + return ret;
> > +
> > + return 0;
> > +}
> > +
> > +static void panel_bridge_detach(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > +
> > + drm_panel_detach(panel_bridge->panel);
> > +}
> > +
> > +static void panel_bridge_pre_enable(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > +
> > + drm_panel_prepare(panel_bridge->panel);
> > +}
> > +
> > +static void panel_bridge_enable(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > +
> > + drm_panel_enable(panel_bridge->panel);
> > +}
> > +
> > +static void panel_bridge_disable(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > +
> > + drm_panel_disable(panel_bridge->panel);
> > +}
> > +
> > +static void panel_bridge_post_disable(struct drm_bridge *bridge)
> > +{
> > + struct panel_bridge *panel_bridge =
drm_bridge_to_panel_bridge(bridge);
> > +
> > + drm_panel_unprepare(panel_bridge->panel);
> > +}
> > +
> > +static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
> > + .attach = panel_bridge_attach,
> > + .detach = panel_bridge_detach,
> > + .pre_enable = panel_bridge_pre_enable,
> > + .enable = panel_bridge_enable,
> > + .disable = panel_bridge_disable,
> > + .post_disable = panel_bridge_post_disable,
> > +};
> > +
> > +/**
> > + * drm_panel_bridge_add - Creates a drm_bridge and drm_connector that
> > + * just call the appropriate functions from drm_panel.
> > + *
> > + * @dev: The struct device of the panel device. This is used for
> > + * registering the drm_bridge.
> > + * @panel: The drm_panel being wrapped. Must be non-NULL.
> > + * @connector_type: The DRM_MODE_CONNECTOR_* for the connector to be
> > + * created.
> > + *
> > + * For drivers converting from directly using drm_panel: The expected
> > + * usage pattern is that during either encoder module probe or DSI
> > + * host attach, a drm_panel will be looked up through
> > + * drm_of_find_panel_or_bridge(). drm_panel_bridge_add() is used to
> > + * wrap that panel in the new bridge, and the result can then be
> > + * passed to drm_bridge_attach(). The drm_panel_prepare() and related
> > + * functions can be dropped from the encoder driver (they're now
> > + * called by the KMS helpers before calling into the encoder), along
> > + * with connector creation.
>
> +panel/bridge reviewers.

Thank you for that.

> This does make things much cleaner, but it seems a bit strange to create
> a drm_bridge when there isn't really a HW bridge in the display chain (i.e,
> when the DSI encoder is directly connected to a DSI panel).

I agree with you. I don't think this is a good idea, and what I'd like to see
is a refactoring of the panel and bridge ops that would make them more alike,
allowing to handle bridges and panels through a common interface.

Another reason to go in that direction is that, if we create an object that
can expose both encoder-related and connector-related operations (bridges
being geared towards the former and panel the latter at the moment), then
we'll be able to handle connector creation in a much easier better way. As
I've explained before, bridges should not create connectors, as they have no
idea whether they're chained to another bridge or output directly to a
connector.

> There are kms drivers that use drm_panel, but don't have simple stub
> connectors that wrap around a drm_panel. They have more complicated
> connector ops, and may call drm_panel_prepare() and related functions a bit
> differently. We won't be able to use drm_panel_bridge for those drivers.
>
> For msm, we check whether the DSI encoder is connected directly to a panel
> or an external bridge. If it's connected to an external bridge, we skip the
> creation of the stub connector, and rely on the external bridge driver to
> create the connector:
>
> http://lxr.free-electrons.com/source/drivers/gpu/drm/msm/dsi/dsi.c#L227
>
> The msm solution isn't very neat, but it avoids the need to create another
> bridge to glue things together.
>
> Archit
>
> > + */
> > +struct drm_bridge *drm_panel_bridge_add(struct device *dev,
> > + struct drm_panel *panel,
> > + u32 connector_type)
> > +{
> > + struct panel_bridge *panel_bridge =
> > + devm_kzalloc(dev, sizeof(*panel_bridge), GFP_KERNEL);
> > + int ret;tegra_output_connector_detect,
> > +
> > + if (!dev || !panel)
> > + return ERR_PTR(EINVAL);
> > +
> > + panel_bridge->dev = dev;
> > + panel_bridge->connector_type = connector_type;
> > + panel_bridge->panel = panel;
> > +
> > + panel_bridge->bridge.funcs = &panel_bridge_bridge_funcs;
> > + panel_bridge->bridge.of_node = dev->of_node;
> > +
> > + ret = drm_bridge_add(&panel_bridge->bridge);
> > + if (ret)
> > + return ERR_PTR(ret);
> > +
> > + return &panel_bridge->bridge;
> > +}
> > +EXPORT_SYMBOL(drm_panel_bridge_add);
> > +
> > +void drm_panel_bridge_remove(struct device *dev, struct drm_bridge
> > *bridge) +{
> > + drm_bridge_remove(bridge);
> > + devm_kfree(dev, bridge);
> > +}
> > +EXPORT_SYMBOL(drm_panel_bridge_remove);
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index fdd82fcbf168..e08563ee0546 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -29,6 +29,7 @@
> > #include <drm/drm_modes.h>
> >
> > struct drm_bridge;
> > +struct drm_panel;
> >
> > /**
> > * struct drm_bridge_funcs - drm_bridge control functions
> > @@ -221,4 +222,11 @@ void drm_bridge_mode_set(struct drm_bridge *bridge,
> > void drm_bridge_pre_enable(struct drm_bridge *bridge);
> > void drm_bridge_enable(struct drm_bridge *bridge);
> >
> > +#ifdef CONFIG_DRM_PANEL
> > +struct drm_bridge *drm_panel_bridge_add(struct device *dev,
> > + struct drm_panel *panel,
> > + u32 connector_type);
> > +void drm_panel_bridge_remove(struct device *dev, struct drm_bridge
> > *bridge);
> > +#endif
> > +
> > #endif

--
Regards,

Laurent Pinchart

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