linux-kernel - [PATCH RFC v2 3/5] drm/panel: ilitek-ili9881c: Add support for two-lane configuration

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Message-Id: <20250424-feature_sfto340xc-v2-3-ff7da6192df2@bootlin.com>
Date: Thu, 24 Apr 2025 17:07:41 +0200
From: Kory Maincent <kory.maincent@...tlin.com>
To: Neil Armstrong <neil.armstrong@...aro.org>, 
 Jessica Zhang <quic_jesszhan@...cinc.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Thierry Reding <thierry.reding@...il.com>, 
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 Kory Maincent <kory.maincent@...tlin.com>
Subject: [PATCH RFC v2 3/5] drm/panel: ilitek-ili9881c: Add support for
 two-lane configuration

Enable support for two-lane configuration which is done by setting the
LANSEL_SW_EN and LANSEL_SW bits in the Pad Control register.

Use the data-lanes device tree parameter to configure the number of lanes.
The default configuration remains set to four lanes.

Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
---

Change in v2:
- Read the data-lanes parameter from the port endpoint and use
  drm_of_get_data_lanes_count instead of of_property_read_u32.
---
 drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 33 +++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
index 28cd7560e5db1d5734b10babdb4e4e553c6e07d0..2e38dea28336f445cb6a074dbbec006f0659287a 100644
--- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
+++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
@@ -16,6 +16,7 @@
 
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_modes.h>
+#include <drm/drm_of.h>
 #include <drm/drm_panel.h>
 
 #include <video/mipi_display.h>
@@ -1263,6 +1264,21 @@ static int ili9881c_send_cmd_data(struct ili9881c *ctx, u8 cmd, u8 data)
 	return 0;
 }
 
+static int ili9881c_set_lanes_cfg(struct ili9881c *ctx)
+{
+	int ret;
+
+	if (ctx->dsi->lanes != 2)
+		/* Nothing to do */
+		return 0;
+
+	ret = ili9881c_switch_page(ctx, 1);
+	if (ret)
+		return ret;
+
+	return ili9881c_send_cmd_data(ctx, 0xB7, 0x3);
+}
+
 static int ili9881c_prepare(struct drm_panel *panel)
 {
 	struct ili9881c *ctx = panel_to_ili9881c(panel);
@@ -1295,6 +1311,10 @@ static int ili9881c_prepare(struct drm_panel *panel)
 			return ret;
 	}
 
+	ret = ili9881c_set_lanes_cfg(ctx);
+	if (ret)
+		return ret;
+
 	ret = ili9881c_switch_page(ctx, 0);
 	if (ret)
 		return ret;
@@ -1503,8 +1523,9 @@ static const struct drm_panel_funcs ili9881c_funcs = {
 
 static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
 {
+	struct device_node *endpoint;
 	struct ili9881c *ctx;
-	int ret;
+	int ret, lanes;
 
 	ctx = devm_kzalloc(&dsi->dev, sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
@@ -1545,11 +1566,19 @@ static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
 	if (ret)
 		return ret;
 
+	endpoint = of_graph_get_endpoint_by_regs(dsi->dev.of_node, -1, -1);
+	lanes = drm_of_get_data_lanes_count(endpoint, 2, 4);
+	of_node_put(endpoint);
+	if (lanes == -EINVAL)
+		lanes = 4;
+	else if (lanes < 0)
+		return lanes;
+
 	drm_panel_add(&ctx->panel);
 
 	dsi->mode_flags = ctx->desc->mode_flags;
 	dsi->format = MIPI_DSI_FMT_RGB888;
-	dsi->lanes = 4;
+	dsi->lanes = lanes;
 
 	return mipi_dsi_attach(dsi);
 }

-- 
2.34.1