Message-ID: <1b9bf191-3cb6-cba3-01e5-9f4a7ec86432@codeaurora.org>
Date:   Fri, 12 May 2017 15:45:14 +0530
From:   Archit Taneja <architt@...eaurora.org>
To:     Eric Anholt <eric@...olt.net>, dri-devel@...ts.freedesktop.org,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        CK Hu <ck.hu@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Yannick Fertre <yannick.fertre@...com>,
        Philippe Cornu <philippe.cornu@...com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] drm/bridge: Refactor out the panel wrapper from
 the lvds-encoder bridge.

Hi,

On 05/12/2017 12:01 AM, 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.
>
> v2: Fix build with CONFIG_DRM=m, drop "dev" argument that should just
>     be the panel's dev, move kerneldoc up a level and document
>     _remove().
>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
> ---
>  Documentation/gpu/drm-kms-helpers.rst |   6 ++
>  drivers/gpu/drm/Makefile              |   1 +
>  drivers/gpu/drm/bridge/Kconfig        |  11 +-
>  drivers/gpu/drm/bridge/lvds-encoder.c | 157 ++++-----------------------
>  drivers/gpu/drm/bridge/panel.c        | 197 ++++++++++++++++++++++++++++++++++
>  include/drm/drm_bridge.h              |   7 ++
>  6 files changed, 238 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..7c5e2549a58a 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -143,6 +143,12 @@ Bridge Helper Reference
>  .. kernel-doc:: drivers/gpu/drm/drm_bridge.c
>     :export:
>
> +Panel-Bridge Helper Reference
> +-----------------------------
> +
> +.. kernel-doc:: drivers/gpu/drm/bridge/panel.c
> +   :export:
> +
>  .. _drm_panel_helper:
>
>  Panel Helper Reference
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index c156fecfb362..4cc9c02cc3f2 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -24,6 +24,7 @@ drm-$(CONFIG_COMPAT) += drm_ioc32.o
>  drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o
>  drm-$(CONFIG_PCI) += ati_pcigart.o
>  drm-$(CONFIG_DRM_PANEL) += drm_panel.o
> +drm-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
>  drm-$(CONFIG_OF) += drm_of.o
>  drm-$(CONFIG_AGP) += drm_agpsupport.o
>  drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
> 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/lvds-encoder.c b/drivers/gpu/drm/bridge/lvds-encoder.c
> index f1f67a279426..0903ba574f61 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 +35,34 @@ 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(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..fd1a78cb1205
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -0,0 +1,197 @@
> +/*
> + * Copyright (C) 2016 Laurent Pinchart <laurent.pinchart@...asonboard.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 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 = {

This can be wrapped to 80 lines to prevent checkpatch warnings.

> +	.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 calls the appropriate functions from drm_panel.
> + *
> + * @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.  When done with the bridge,
> + * drm_bridge_detach() should be called as normal, then
> + * drm_panel_bridge_remove() to free it.
> + */
> +struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
> +					u32 connector_type)

There are more arguments besides the connector_type that we may require
to create the connector correctly. Things like connector's 'bus_formats'
and 'polled' fields need to come from the caller. I guess they don't matter
as much for simple panels, but we'd probably want to wrap them all in a
struct in the future.

> +{
> +	struct panel_bridge *panel_bridge;
> +	int ret;
> +
> +	if (!panel)
> +		return ERR_PTR(EINVAL);
> +
> +	panel_bridge = devm_kzalloc(panel->dev, sizeof(*panel_bridge),
> +				    GFP_KERNEL);
> +	if (!panel_bridge)
> +		return ERR_PTR(-ENOMEM);
> +
> +	panel_bridge->connector_type = connector_type;
> +	panel_bridge->panel = panel;
> +
> +	panel_bridge->bridge.funcs = &panel_bridge_bridge_funcs;
> +	panel_bridge->bridge.of_node = panel->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);
> +
> +/**
> + * drm_panel_bridge_remove - Unregisters and frees a drm_bridge
> + * created by drm_panel_bridge_add().
> + *
> + * @bridge: The drm_bridge being freed.
> + */
> +void drm_panel_bridge_remove(struct drm_bridge *bridge)
> +{
> +	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
> +
> +	drm_bridge_remove(bridge);
> +	devm_kfree(panel_bridge->panel->dev, bridge);
> +}
> +EXPORT_SYMBOL(drm_panel_bridge_remove);
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index fdd82fcbf168..bad2178ea3e0 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 +222,10 @@ 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 drm_panel *panel,
> +					u32 connector_type);
> +void drm_panel_bridge_remove(struct drm_bridge *bridge);
> +#endif

Shouldn't this be CONFIG_DRM_PANEL_BRIDGE?

As I mentioned on irc, I was facing some build issues with this patch
applied. Once we sort that out:

Acked-by: Archit Taneja <architt@...eaurora.org>

Thanks,
Archit


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