drm/panel-jdi-lt070me050000: Don't control backlight when off

If the display has never been powered up, or been powered dow
via unprepare, then don't allow the backlight subsystem to try
and send DSI commands to the powered down panel.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

drivers/gpu/drm/panel/panel-jdi-lt070me05000.c

@@ -279,10 +279,10 @@ static int jdi_panel_enable(struct drm_panel *panel)
 	if (jdi->enabled)
 		return 0;
 
-	backlight_enable(jdi->backlight);
-
 	jdi->enabled = true;
 
+	backlight_enable(jdi->backlight);
+
 	return 0;
 }
 
@@ -326,10 +326,14 @@ static int jdi_panel_get_modes(struct drm_panel *panel,
 
 static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
 {
-	struct mipi_dsi_device *dsi = bl_get_data(bl);
+	struct jdi_panel *jdi = bl_get_data(bl);
+	struct mipi_dsi_device *dsi = jdi->dsi;
 	int ret;
 	u16 brightness = bl->props.brightness;
 
+	if (!jdi->enabled)
+		return brightness;
+
 	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
 	ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness);
@@ -343,9 +347,13 @@ static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
 
 static int dsi_dcs_bl_update_status(struct backlight_device *bl)
 {
-	struct mipi_dsi_device *dsi = bl_get_data(bl);
+	struct jdi_panel *jdi = bl_get_data(bl);
+	struct mipi_dsi_device *dsi = jdi->dsi;
 	int ret;
 
+	if (!jdi->enabled)
+		return 0;
+
 	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
 	ret = mipi_dsi_dcs_set_display_brightness(dsi, bl->props.brightness);
@@ -363,8 +371,9 @@ static const struct backlight_ops dsi_bl_ops = {
 };
 
 static struct backlight_device *
-drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi)
+drm_panel_create_dsi_backlight(struct jdi_panel *jdi)
 {
+	struct mipi_dsi_device *dsi = jdi->dsi;
 	struct device *dev = &dsi->dev;
 	struct backlight_properties props;
 
@@ -373,7 +382,7 @@ drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi)
 	props.brightness = 255;
 	props.max_brightness = 255;
 
-	return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
+	return devm_backlight_device_register(dev, dev_name(dev), dev, jdi,
 					      &dsi_bl_ops, &props);
 }
 
@@ -424,7 +433,7 @@ static int jdi_panel_add(struct jdi_panel *jdi)
 		return dev_err_probe(dev, PTR_ERR(jdi->dcdc_en_gpio),
 				     "cannot get dcdc-en-gpio %d\n", ret);
 
-	jdi->backlight = drm_panel_create_dsi_backlight(jdi->dsi);
+	jdi->backlight = drm_panel_create_dsi_backlight(jdi);
 	if (IS_ERR(jdi->backlight))
 		return dev_err_probe(dev, PTR_ERR(jdi->backlight),
 				     "failed to register backlight %d\n", ret);