[PATCH 2/7] drm/mediatek: fix CCORR mtk_ctm_s31_32_to_s1_n function issue

[Jay Liu]

if matrixbit is 11,
The range of color matrix is from 0 to (BIT(11) - 1).
Values from 0 to (BIT(11) - 1) represent positive numbers,
values from BIT(11) to (BIT(12) - 1) represent negative numbers.
For example, -1 need converted to 8191.

Fixes: 738ed4156fba ("drm/mediatek: Add matrix_bits private data for ccorr")

Signed-off-by: Jay Liu <jay.liu at mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_disp_ccorr.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ccorr.c b/drivers/gpu/drm/mediatek/mtk_disp_ccorr.c
index 94e82b3fa2d8..a9f91b71534b 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_ccorr.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_ccorr.c
@@ -100,6 +100,15 @@ static u16 mtk_ctm_s31_32_to_s1_n(u64 in, u32 n)
 		r |= (in >> (32 - n)) & GENMASK(n, 0);
 	}
 
+	/*
+	 *The range of r is from 0 to (BIT(n + 1) - 1),
+	 *where values from 0 to (BIT(n) - 1) represent positive numbers,
+	 *and values from BIT(n) to (BIT(n + 1) - 1) represent negative numbers.
+	 *For example, if n is 11, -1 will be converted to 8191.
+	 */
+	if (r & BIT(n + 1))
+		r = (~(r & GENMASK(n, 0)) + 1) & GENMASK(n + 1, 0);
+
 	return r;
 }
 
-- 
2.18.0