linux-kernel - [PATCH v3 2/2] drm/bridge: parade-ps8640: Populate devices on aux-bus

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Message-Id: <20211026121058.v3.2.I09899dea340f11feab97d719cb4b62bef3179e4b@changeid>
Date:   Tue, 26 Oct 2021 12:11:10 -0700
From:   Philip Chen <philipchen@...omium.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     dianders@...omium.org, swboyd@...omium.org,
        Philip Chen <philipchen@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH v3 2/2] drm/bridge: parade-ps8640: Populate devices on aux-bus

Conventionally, panel is listed under the root of the device tree.
When userland asks for display mode, ps8640 bridge is responsible
for returning EDID when ps8640_bridge_get_edid() is called.

Now enable a new option of listing panel under "aux-bus" of ps8640
bridge node in the device tree. In this case, panel driver can retrieve
EDID by triggering AUX transactions, without ps8640_bridge_get_edid()
calls at all.

To prevent the "old" and "new" options from interfering with each
other's logic flow, disable DRM_BRIDGE_OP_EDID when the new option
is taken.

Signed-off-by: Philip Chen <philipchen@...omium.org>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
---

Changes in v3:
- Fix when to call of_node_put() in ps8640_of_panel_on_aux_bus()

Changes in v2:
- Add of_node_put() calls in ps8640_of_panel_on_aux_bus()
- Select DRM_DP_AUX_BUS for PS8640 driver in Kconfig
- Replace _put_sync() with _put_sync_suspend() in ps8640_post_disable()

 drivers/gpu/drm/bridge/Kconfig         |  1 +
 drivers/gpu/drm/bridge/parade-ps8640.c | 53 +++++++++++++++++++-------
 2 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 431b6e12a81f..61db5a66b493 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -182,6 +182,7 @@ config DRM_PARADE_PS8622
 config DRM_PARADE_PS8640
 	tristate "Parade PS8640 MIPI DSI to eDP Converter"
 	depends on OF
+	select DRM_DP_AUX_BUS
 	select DRM_KMS_HELPER
 	select DRM_MIPI_DSI
 	select DRM_PANEL
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index ac42a3473770..e737f1a27f30 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -14,6 +14,7 @@
 #include <linux/regulator/consumer.h>
 
 #include <drm/drm_bridge.h>
+#include <drm/drm_dp_aux_bus.h>
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_of.h>
@@ -149,7 +150,24 @@ static inline struct ps8640 *aux_to_ps8640(struct drm_dp_aux *aux)
 	return container_of(aux, struct ps8640, aux);
 }
 
-static void ps8640_ensure_hpd(struct ps8640 *ps_bridge)
+static bool ps8640_of_panel_on_aux_bus(struct device *dev)
+{
+	struct device_node *bus, *panel;
+
+	bus = of_get_child_by_name(dev->of_node, "aux-bus");
+	if (!bus)
+		return false;
+
+	panel = of_get_child_by_name(bus, "panel");
+	of_node_put(bus);
+	if (!panel)
+		return false;
+	of_node_put(panel);
+
+	return true;
+}
+
+static int ps8640_ensure_hpd(struct ps8640 *ps_bridge)
 {
 	struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
 	struct device *dev = &ps_bridge->page[PAGE2_TOP_CNTL]->dev;
@@ -556,17 +574,6 @@ static int ps8640_probe(struct i2c_client *client)
 	if (!ps_bridge)
 		return -ENOMEM;
 
-	/* port@1 is ps8640 output port */
-	ret = drm_of_find_panel_or_bridge(np, 1, 0, &panel, NULL);
-	if (ret < 0)
-		return ret;
-	if (!panel)
-		return -ENODEV;
-
-	ps_bridge->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
-	if (IS_ERR(ps_bridge->panel_bridge))
-		return PTR_ERR(ps_bridge->panel_bridge);
-
 	ps_bridge->supplies[0].supply = "vdd33";
 	ps_bridge->supplies[1].supply = "vdd12";
 	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ps_bridge->supplies),
@@ -589,9 +596,16 @@ static int ps8640_probe(struct i2c_client *client)
 
 	ps_bridge->bridge.funcs = &ps8640_bridge_funcs;
 	ps_bridge->bridge.of_node = dev->of_node;
-	ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;
 	ps_bridge->bridge.type = DRM_MODE_CONNECTOR_eDP;
 
+	/*
+	 * In the device tree, if panel is listed under aux-bus of the bridge
+	 * node, panel driver should be able to retrieve EDID by itself using
+	 * aux-bus. So let's not set DRM_BRIDGE_OP_EDID here.
+	 */
+	if (!ps8640_of_panel_on_aux_bus(&client->dev))
+		ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;
+
 	ps_bridge->page[PAGE0_DP_CNTL] = client;
 
 	ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config);
@@ -630,6 +644,19 @@ static int ps8640_probe(struct i2c_client *client)
 	if (ret)
 		return ret;
 
+	devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux);
+
+	/* port@1 is ps8640 output port */
+	ret = drm_of_find_panel_or_bridge(np, 1, 0, &panel, NULL);
+	if (ret < 0)
+		return ret;
+	if (!panel)
+		return -ENODEV;
+
+	ps_bridge->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
+	if (IS_ERR(ps_bridge->panel_bridge))
+		return PTR_ERR(ps_bridge->panel_bridge);
+
 	drm_bridge_add(&ps_bridge->bridge);
 
 	return 0;
-- 
2.33.0.1079.g6e70778dc9-goog