drm/panel: samsung-s6288a0: Add initial backlight support

Add basic support for controlling the panel's backlight via
setting of the "AID" parameter with DSI DCS commands

Signed-off-by: Celeste Lucero <[email protected]>

drivers/gpu/drm/panel/msm8916-generated/panel-samsung-s6288a0.c

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
-// Copyright (c) 2023 FIXME
+// Copyright (c) 2024 FIXME
 // Generated with linux-mdss-dsi-panel-driver-generator from vendor device tree:
-// Copyright (c) 2013, The Linux Foundation. All rights reserved. (FIXME)
+// Copyright (c) 2013-2014, The Linux Foundation. All rights reserved.
 
 #include <linux/backlight.h>
 #include <linux/delay.h>
@@ -17,6 +17,11 @@
 #include <drm/drm_panel.h>
 #include <drm/drm_probe_helper.h>
 
+//From downstream dt property "samsung,panel-aid-cmds-list-350"
+#define AID_MIN 8
+#define AID_MAX 785
+#define MAX_BRIGHTNESS (AID_MAX - AID_MIN)
+
 struct samsung {
  struct drm_panel panel;
  struct mipi_dsi_device *dsi;
@@ -40,6 +45,29 @@ static void samsung_reset(struct samsung *ctx)
  usleep_range(10000, 11000);
 }
 
+static int samsung_send_dcs_aid(struct mipi_dsi_device *dsi, u16 brightness)
+{
+ u8 payload[5] = { 0x40, 0x08, 0x20, 0, 0 };
+ int ret;
+ u16 aid;
+
+ //Calculate AID value from brightness level
+ if (brightness > MAX_BRIGHTNESS)
+ brightness = MAX_BRIGHTNESS;
+ aid = (MAX_BRIGHTNESS - brightness) + AID_MIN;
+ payload[3] = (aid >> 8) & 0xff;
+ payload[4] = aid & 0xff;
+
+ //Set AID
+ ret = mipi_dsi_dcs_write(dsi, 0xb2, payload, sizeof(payload));
+ if (ret < 0) {
+ dev_err(&dsi->dev, "Failed to set AID: %d\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
 static int samsung_on(struct samsung *ctx)
 {
  struct mipi_dsi_device *dsi = ctx->dsi;
@@ -48,7 +76,9 @@ static int samsung_on(struct samsung *ctx)
 
  dsi->mode_flags |= MIPI_DSI_MODE_LPM;
 
+ //Tesk key ON - Enable level 1 control commands
  mipi_dsi_dcs_write_seq(dsi, 0xf0, 0x5a, 0x5a);
+ //Enable level 2 control commands
  mipi_dsi_dcs_write_seq(dsi, 0xfc, 0x5a, 0x5a);
 
  ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
@@ -58,17 +88,37 @@ static int samsung_on(struct samsung *ctx)
  }
  msleep(120);
 
+ //AVDD Setting
  mipi_dsi_dcs_write_seq(dsi, 0xb8, 0x38, 0x0b, 0x30);
+
+ //Brightness gamma
  mipi_dsi_dcs_write_seq(dsi, 0xca,
- 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x80, 0x80,
- 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
- 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
- 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x00, 0x00,
- 0x00);
- mipi_dsi_dcs_write_seq(dsi, 0xb2, 0x40, 0x08, 0x20, 0x00, 0x08);
+ 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, // V255 RGB
+ 0x80, 0x80, 0x80, // V203 RGB
+ 0x80, 0x80, 0x80, // V151 RGB
+ 0x80, 0x80, 0x80, // V87 RGB
+ 0x80, 0x80, 0x80, // V51 RGB
+ 0x80, 0x80, 0x80, // V35 RGB
+ 0x80, 0x80, 0x80, // V23 RGB
+ 0x80, 0x80, 0x80, // V11 RGB
+ 0x80, 0x80, 0x80, // V3 RGB
+ 0x00, 0x00, 0x00); // VT RGB
+
+ //Set AID
+ // We need the actual backlight value even while blank, hence why the
+ // value is read directly instead of via backlight_get_brightness()
+ samsung_send_dcs_aid(dsi, ctx->panel.backlight->props.brightness);
+
+ //Set ELVSS condition
  mipi_dsi_dcs_write_seq(dsi, 0xb6, 0x28, 0x0b);
+
+ //Set ACL
  mipi_dsi_dcs_write_seq(dsi, MIPI_DCS_WRITE_POWER_SAVE, 0x00);
+
+ //Update gamma, LTPS(AID)
  mipi_dsi_dcs_write_seq(dsi, 0xf7, 0x03);
+
+ //Disable level 2 control commands
  mipi_dsi_dcs_write_seq(dsi, 0xfc, 0xa5, 0xa5);
 
  ret = mipi_dsi_dcs_set_display_on(dsi);
@@ -88,6 +138,9 @@ static int samsung_off(struct samsung *ctx)
 
  dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
+ //Tesk key OFF - Disable level 1 control commands
+ mipi_dsi_dcs_write_seq(dsi, 0xf0, 0xa5, 0xa5);
+
  ret = mipi_dsi_dcs_set_display_off(dsi);
  if (ret < 0) {
  dev_err(dev, "Failed to set display off: %d\n", ret);
@@ -184,42 +237,29 @@ static const struct drm_panel_funcs samsung_panel_funcs = {
 static int samsung_bl_update_status(struct backlight_device *bl)
 {
  struct mipi_dsi_device *dsi = bl_get_data(bl);
- u16 brightness = backlight_get_brightness(bl);
  int ret;
+ u16 brightness = backlight_get_brightness(bl);
 
  dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
- ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
- if (ret < 0)
+ //Set AID
+ ret = samsung_send_dcs_aid(dsi, brightness);
+ if (ret != 0)
  return ret;
 
- dsi->mode_flags |= MIPI_DSI_MODE_LPM;
-
- return 0;
-}
-
-// TODO: Check if /sys/class/backlight/.../actual_brightness actually returns
-// correct values. If not, remove this function.
-static int samsung_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;
+ //Update gamma, LTPS(AID)
+ mipi_dsi_dcs_write_seq(dsi, 0xf7, 0x03);
 
- ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness);
- if (ret < 0)
- return ret;
+ //TODO: downstream driver also updates ACL and ELVSS based on brightness
+ // check out dsi-panel-samsung-wvga-video.dtsi
 
  dsi->mode_flags |= MIPI_DSI_MODE_LPM;
 
- return brightness & 0xff;
+ return 0;
 }
 
 static const struct backlight_ops samsung_bl_ops = {
  .update_status = samsung_bl_update_status,
- .get_brightness = samsung_bl_get_brightness,
 };
 
 static struct backlight_device *
@@ -228,8 +268,8 @@ samsung_create_backlight(struct mipi_dsi_device *dsi)
  struct device *dev = &dsi->dev;
  const struct backlight_properties props = {
  .type = BACKLIGHT_RAW,
- .brightness = 255,
- .max_brightness = 255,
+ .brightness = MAX_BRIGHTNESS,
+ .max_brightness = MAX_BRIGHTNESS,
  };
 
  return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
@@ -264,7 +304,7 @@ static int samsung_probe(struct mipi_dsi_device *dsi)
  dsi->lanes = 2;
  dsi->format = MIPI_DSI_FMT_RGB888;
  dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
- MIPI_DSI_MODE_NO_EOT_PACKET;
+ MIPI_DSI_MODE_NO_EOT_PACKET | MIPI_DSI_MODE_VIDEO_NO_HFP;
 
  drm_panel_init(&ctx->panel, dev, &samsung_panel_funcs,
  DRM_MODE_CONNECTOR_DSI);