[PATCH 2/2] drm/mediatek: dpi/dsi: fix possible_crtcs calculation

[Michael Walle <mwalle@kernel.org>]

mtk_drm_find_possible_crtc_by_comp() assumed that the main path will
always have the CRTC with id 0, the ext id 1 and the third id 2. This
is only true if the paths are all available. But paths are optional (see
also comment in mtk_drm_kms_init()), e.g. the main path might not be
enabled or available at all. Then the CRTC IDs will shift one up, e.g.
ext will be 1 and the third path will be 2.

To fix that, dynamically calculate the IDs by the precence of the paths.

Fixes: 5aa8e7647676 ("drm/mediatek: dpi/dsi: Change the getting possible_crtc way")
Suggested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Michael Walle <mwalle@kernel.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 41 ++++++++++++++-------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
index 771f4e173353..f3064bff64e8 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
@@ -526,21 +526,34 @@ unsigned int mtk_drm_find_possible_crtc_by_comp(struct drm_device *drm,
 						struct device *dev)
 {
 	struct mtk_drm_private *private = drm->dev_private;
-	unsigned int ret = 0;
-
-	if (mtk_drm_find_comp_in_ddp(dev, private->data->main_path, private->data->main_len,
-				     private->ddp_comp))
-		ret = BIT(0);
-	else if (mtk_drm_find_comp_in_ddp(dev, private->data->ext_path,
-					  private->data->ext_len, private->ddp_comp))
-		ret = BIT(1);
-	else if (mtk_drm_find_comp_in_ddp(dev, private->data->third_path,
-					  private->data->third_len, private->ddp_comp))
-		ret = BIT(2);
-	else
-		DRM_INFO("Failed to find comp in ddp table\n");
+	int i = 0;
+
+	if (private->data->main_path) {
+		if (mtk_drm_find_comp_in_ddp(dev, private->data->main_path,
+					     private->data->main_len,
+					     private->ddp_comp))
+			return BIT(i);
+		i++;
+	}
+
+	if (private->data->ext_path) {
+		if (mtk_drm_find_comp_in_ddp(dev, private->data->ext_path,
+					     private->data->ext_len,
+					     private->ddp_comp))
+			return BIT(i);
+		i++;
+	}
 
-	return ret;
+	if (private->data->third_path) {
+		if (mtk_drm_find_comp_in_ddp(dev, private->data->third_path,
+					     private->data->third_len,
+					     private->ddp_comp))
+			return BIT(i);
+		i++;
+	}
+
+	DRM_INFO("Failed to find comp in ddp table\n");
+	return 0;
 }
 
 int mtk_ddp_comp_init(struct device_node *node, struct mtk_ddp_comp *comp,
-- 
2.39.2