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

[Kory Maincent]

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.mainc...@bootlin.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