drm/mediatek: dpi/dsi: Fix possible_crtcs calculation

mtk_find_possible_crtcs() assumes 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 0 and the third path will be 1.

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

While at it, make the return code a signed one and return -ENODEV if no
path is found and handle the error in the callers.

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>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240606092122.2026313-1-mwalle@kernel.org/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gpu/drm/mediatek/mtk_ddp_comp.h b/drivers/gpu/drm/mediatek/mtk_ddp_comp.h
index f7fe2e08dc8e..ecf6dc283cd7 100644
--- a/drivers/gpu/drm/mediatek/mtk_ddp_comp.h
+++ b/drivers/gpu/drm/mediatek/mtk_ddp_comp.h
@@ -330,7 +330,7 @@ static inline void mtk_ddp_comp_encoder_index_set(struct mtk_ddp_comp *comp)
 
 int mtk_ddp_comp_get_id(struct device_node *node,
 			enum mtk_ddp_comp_type comp_type);
-unsigned int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev);
+int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev);
 int mtk_ddp_comp_init(struct device_node *comp_node, struct mtk_ddp_comp *comp,
 		      unsigned int comp_id);
 enum mtk_ddp_comp_type mtk_ddp_comp_get_type(unsigned int comp_id);