[PATCH 42/42] drm/mediatek: mtk_drm_drv: Fail init only if all paths are invalid

[AngeloGioacchino Del Regno]

Up until now, if not all display controller paths were valid, the
driver would fail probing and refuse to bind components: while
that was a good idea before, now that mediatek-drm gained much
more flexibility, it is finally possible to gracefully handle
this situation and register only the valid paths while leaving
the invalid ones unregistered, without any crash.

Count how many output paths are found, and then count how many
have failed probing: if there is at least one valid path, avoid
erroring out, so that at least some outputs will just work.

Of course, any path failing is not a clean situation and must be
resolved: in this case, function mtk_crtc_create() still prints
error messages so, even though some output works, that will not
go unnoticed, as a quick check in kmsg will show the errors that
made a certain path not to register.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index f5c9fe1588d0..65a891815408 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -379,6 +379,8 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	struct mtk_drm_private *priv_n;
 	struct device *dma_dev = NULL;
 	struct drm_crtc *crtc;
+	int num_failed = 0;
+	int num_paths = 0;
 	int ret, i, j;
 
 	if (drm_firmware_drivers_only())
@@ -445,15 +447,29 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 			if (!priv_n->data->output_paths[i].len)
 				continue;
 
+			num_paths++;
+
+			dev_vdbg(drm->dev,
+				 "[CTRL%d-CRTC%d] Path Len:%d, Controller Order:%u\n",
+				 j, i, priv_n->data->output_paths[i].len,
+				 priv_n->data->output_paths[i].order);
+
 			ret = mtk_crtc_create(drm, i, j,
 					      priv_n->data->conn_routes,
 					      priv_n->data->num_conn_routes);
+			if (ret == 0)
+				break;
 
-			if (ret)
-				goto err_component_unbind;
+			num_failed++;
 		}
 	}
 
+	if (num_failed == num_paths) {
+		dev_err(drm->dev, "No valid Display Controller path! Going out.\n");
+		ret = -ENODEV;
+		goto err_component_unbind;
+	}
+
 	/* IGT will check if the cursor size is configured */
 	drm->mode_config.cursor_width = 512;
 	drm->mode_config.cursor_height = 512;
-- 
2.54.0