linux-kernel - [RFC PATCH 3/3] drm: bridge: lvds-encoder: on request, override the bus format

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Message-Id: <20180317221525.18534-4-peda@axentia.se>
Date:   Sat, 17 Mar 2018 23:15:25 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Rosin <peda@...ntia.se>, David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Sean Paul <seanpaul@...omium.org>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org
Subject: [RFC PATCH 3/3] drm: bridge: lvds-encoder: on request, override the bus format

If the bridge changes the bus format, allow this to be described in
the bridge, instead of providing false information about the bus
format of the panel itself.

Signed-off-by: Peter Rosin <peda@...ntia.se>
---
 .../bindings/display/bridge/lvds-transmitter.txt       |  8 ++++++++
 drivers/gpu/drm/bridge/lvds-encoder.c                  | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
index 9d09190d9210..c0fbe74272e7 100644
--- a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
+++ b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
@@ -29,6 +29,14 @@ Required properties:
 
 	      "ti,ds90c185"
 
+Optional properties:
+
+- interface-pix-fmt:
+	      Override the bus format of the panel, in case the bridge
+	      converts the signals. Recognized formats include:
+
+	      "rgb565"
+
 Required nodes:
 
 This device has two video ports. Their connections are modeled using the OF
diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c b/drivers/gpu/drm/bridge/lvds-encoder.c
index 75b0d3f6e4de..acff3a5b0562 100644
--- a/drivers/gpu/drm/bridge/lvds-encoder.c
+++ b/drivers/gpu/drm/bridge/lvds-encoder.c
@@ -39,6 +39,9 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 	struct device_node *panel_node;
 	struct drm_panel *panel;
 	struct lvds_encoder *lvds_encoder;
+	u32 bus_format = 0;
+	const char *fmt;
+	int ret;
 
 	lvds_encoder = devm_kzalloc(&pdev->dev, sizeof(*lvds_encoder),
 				    GFP_KERNEL);
@@ -79,6 +82,21 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 	if (IS_ERR(lvds_encoder->panel_bridge))
 		return PTR_ERR(lvds_encoder->panel_bridge);
 
+	ret = of_property_read_string(pdev->dev.of_node,
+				      "interface-pix-fmt", &fmt);
+	if (!ret) {
+		if (!strcmp(fmt, "rgb565")) {
+			bus_format = MEDIA_BUS_FMT_RGB565_1X16;
+		} else {
+			dev_dbg(&pdev->dev,
+				"requested interface-pix-fmt not recognized\n");
+			return -EINVAL;
+		}
+	}
+	if (bus_format)
+		drm_panel_bridge_set_bus_format(lvds_encoder->panel_bridge,
+						bus_format);
+
 	/* The panel_bridge bridge is attached to the panel's of_node,
 	 * but we need a bridge attached to our of_node for our user
 	 * to look up.
-- 
2.11.0