[PATCH 3/5] drm/panel: nt36523: Add DCS backlight support

[Konrad Dybcio]

This chip supports controlling the backlight via DCS commands, on at
least some panels. Add support for doing so.

Note this may only concern the NT36523*W* variant. Nobody knows, really,
there's no docs.

Signed-off-by: Konrad Dybcio <konrad.dyb...@linaro.org>
---
 drivers/gpu/drm/panel/panel-novatek-nt36523.c | 67 +++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-novatek-nt36523.c 
b/drivers/gpu/drm/panel/panel-novatek-nt36523.c
index d30dbbfb67b1..3c81ec014eef 100644
--- a/drivers/gpu/drm/panel/panel-novatek-nt36523.c
+++ b/drivers/gpu/drm/panel/panel-novatek-nt36523.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2022, 2023 Jianhua Lu <lujianhua...@gmail.com>
  */
 
+#include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
@@ -53,6 +54,7 @@ struct panel_desc {
        int (*init_sequence)(struct panel_info *pinfo);
 
        bool is_dual_dsi;
+       bool has_dcs_backlight;
 };
 
 static inline struct panel_info *to_panel_info(struct drm_panel *panel)
@@ -679,6 +681,58 @@ static const struct drm_panel_funcs nt36523_panel_funcs = {
        .get_modes = nt36523_get_modes,
 };
 
+static int nt36523_bl_update_status(struct backlight_device *bl)
+{
+       struct mipi_dsi_device *dsi = bl_get_data(bl);
+       u16 brightness = backlight_get_brightness(bl);
+       int ret;
+
+       dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+       ret = mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
+       if (ret < 0)
+               return ret;
+
+       dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+       return 0;
+}
+
+static int nt36523_bl_get_brightness(struct backlight_device *bl)
+{
+       struct mipi_dsi_device *dsi = bl_get_data(bl);
+       u16 brightness;
+       int ret;
+
+       dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+       ret = mipi_dsi_dcs_get_display_brightness_large(dsi, &brightness);
+       if (ret < 0)
+               return ret;
+
+       dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+       return brightness;
+}
+
+static const struct backlight_ops nt36523_bl_ops = {
+       .update_status = nt36523_bl_update_status,
+       .get_brightness = nt36523_bl_get_brightness,
+};
+
+static struct backlight_device *nt36523_create_backlight(struct 
mipi_dsi_device *dsi)
+{
+       struct device *dev = &dsi->dev;
+       const struct backlight_properties props = {
+               .type = BACKLIGHT_RAW,
+               .brightness = 512,
+               .max_brightness = 4095,
+       };
+
+       return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
+                                             &nt36523_bl_ops, &props);
+}
+
 static int nt36523_probe(struct mipi_dsi_device *dsi)
 {
        struct device *dev = &dsi->dev;
@@ -730,9 +784,16 @@ static int nt36523_probe(struct mipi_dsi_device *dsi)
        mipi_dsi_set_drvdata(dsi, pinfo);
        drm_panel_init(&pinfo->panel, dev, &nt36523_panel_funcs, 
DRM_MODE_CONNECTOR_DSI);
 
-       ret = drm_panel_of_backlight(&pinfo->panel);
-       if (ret)
-               return dev_err_probe(dev, ret, "failed to get backlight\n");
+       if (pinfo->desc->has_dcs_backlight) {
+               pinfo->panel.backlight = nt36523_create_backlight(dsi);
+               if (IS_ERR(pinfo->panel.backlight))
+                       return dev_err_probe(dev, 
PTR_ERR(pinfo->panel.backlight),
+                                            "Failed to create backlight\n");
+       } else {
+               ret = drm_panel_of_backlight(&pinfo->panel);
+               if (ret)
+                       return dev_err_probe(dev, ret, "Failed to get 
backlight\n");
+       }
 
        drm_panel_add(&pinfo->panel);
 

-- 
2.40.0