[PATCH v2 1/2] drm/nouveau/disp: add backlight for ada lovelace

[Angelo Dureghello <angelo@xxxxxxxxxxxxxxxx>]

Add working backlight for "ada lovelace" missing case.

The nvif method is actually not working for this chipset so
used the drm apis. Also, by dpcd, drm layer is calculating a
max brightness of 255, but to get a real correct max brightnes
the maximum must be multiplied by a factor of 16.

Tested to work properly in Legion Lenovo Pro 5

Lenovo Legion 5 Pro 16ARX8
Bios ver LPCN49WW
	 LPEC49WW
SN PF4T63AZ
Nvidia RTX4060 MaxQ/Mobile rev a1 (ADA LOVELACE AD107M)
AMD Ryzen 9 7945HX + Radeon

and wayland.

---
Changes for v2:
- add some comments
- remove x16 multiplication (hack)
- remove forgot debug printk

Signed-off-by: Angelo Dureghello <angelo@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/nouveau/nouveau_backlight.c | 54 +++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
index d47442125fa1..7b7306d18ad7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
+++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
@@ -286,6 +286,56 @@ nv50_backlight_init(struct nouveau_backlight *bl,
 	return 0;
 }
 
+static int
+nv19x_backlight_init(struct nouveau_backlight *bl,
+		     struct nouveau_connector *nv_conn,
+		     struct nouveau_encoder *nv_encoder,
+		     struct backlight_properties *props,
+		     const struct backlight_ops **ops)
+{
+	int ret;
+	u16 current_level;
+	u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE];
+	u8 current_mode;
+	struct nouveau_drm *drm = nouveau_drm(nv_encoder->base.base.dev);
+
+	/*
+	 * nvif functions, so also nvif_outp_bl_get, are not working with this
+	 * connector (return -22), using only drm layer.
+	 */
+	if (nv_conn->type == DCB_CONNECTOR_eDP) {
+
+		ret = drm_dp_dpcd_read(&nv_conn->aux, DP_EDP_DPCD_REV, edp_dpcd,
+				       EDP_DISPLAY_CTL_CAP_SIZE);
+		if (ret < 0)
+			return ret;
+		if (!drm_edp_backlight_supported(edp_dpcd))
+			return -ENODEV;
+
+		ret = drm_edp_backlight_init(&nv_conn->aux, &bl->edp_info, 0, edp_dpcd,
+					 &current_level, &current_mode);
+		if (ret < 0)
+			return ret;
+
+		ret = drm_edp_backlight_enable(&nv_conn->aux, &bl->edp_info, current_level);
+		if (ret < 0) {
+			NV_ERROR(drm, "Failed to enable backlight on %s: %d\n",
+				 nv_conn->base.name, ret);
+			return ret;
+		}
+
+		*ops = &nv50_edp_bl_ops;
+
+		props->max_brightness = bl->edp_info.max;
+		props->brightness = current_level;
+		bl->uses_dpcd = true;
+
+		return 0;
+	}
+
+	return -ENODEV;
+}
+
 int
 nouveau_backlight_init(struct drm_connector *connector)
 {
@@ -332,6 +382,10 @@ nouveau_backlight_init(struct drm_connector *connector)
 		ret = nv50_backlight_init(bl, nouveau_connector(connector),
 					  nv_encoder, &props, &ops);
 		break;
+	case NV_DEVICE_INFO_V0_ADA:
+		ret = nv19x_backlight_init(bl, nouveau_connector(connector),
+					   nv_encoder, &props, &ops);
+		break;
 	default:
 		ret = 0;
 		goto fail_alloc;
-- 
2.44.0