drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.

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().
v3: Fix another breakage with CONFIG_DRM=m, fix breakage with
    CONFIG_OF=n, move protos under CONFIG_DRM_PANEL_BRIDGE, wrap a
    line.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
Acked-by: Archit Taneja <architt@codeaurora.org> (v2)
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170602202514.11900-1-eric@anholt.net

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

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

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
+	depends on 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_BRIDGE
-	select DRM_PANEL
 	help
 	  Support for transparent parallel to LVDS encoders that don't require
 	  any configuration.

drivers/gpu/drm/bridge/lvds-encoder.c

@@ -8,144 +8,18 @@
  */
 
 #include <drm/drmP.h>
-#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.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>
 
 #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;
+	struct device_node *panel_node;
-
+	struct drm_panel *panel;
-	lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
+	struct drm_bridge *bridge;
-	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;
 
 	/* 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);
+	panel = of_drm_find_panel(panel_node);
-	of_node_put(panel);
+	of_node_put(panel_node);
-	if (!lvds->panel) {
+	if (!panel) {
 		dev_dbg(&pdev->dev, "panel not found, deferring probe\n");
 		return -EPROBE_DEFER;
 	}
 
-	/* Register the bridge. */
+	bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_LVDS);
-	return drm_bridge_add(&lvds->bridge);
+	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;
 }

drivers/gpu/drm/bridge/panel.c

@@ -0,0 +1,200 @@
+/*
+ * 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 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 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)
+{
+	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;
+#ifdef CONFIG_OF
+	panel_bridge->bridge.of_node = panel->dev->of_node;
+#endif
+
+	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);

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
@@ -263,4 +264,10 @@ 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_BRIDGE
+struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
+					u32 connector_type);
+void drm_panel_bridge_remove(struct drm_bridge *bridge);
+#endif
+
 #endif