New SoCs, like MT8195, not only may support bigger lookup tables, but
have got a different register layout to support bigger precision:
support specifying the number of `lut_bits` for each SoC and use it
in mtk_gamma_set_common() to perform the right calculation.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
---
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
index 001b98694761..1845bd326a6d 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
@@ -38,6 +38,7 @@ struct mtk_disp_gamma_data {
 	bool has_dither;
 	bool lut_diff;
 	u16 lut_size;
+	u8 lut_bits;
 };
 
 /*
@@ -91,9 +92,9 @@ void mtk_gamma_set(struct device *dev, struct drm_crtc_state *state)
 	for (i = 0; i < gamma->data->lut_size; i++) {
 		struct drm_color_lut diff, hwlut;
 
-		hwlut.red = drm_color_lut_extract(lut[i].red, LUT_BITS_DEFAULT);
-		hwlut.green = drm_color_lut_extract(lut[i].green, LUT_BITS_DEFAULT);
-		hwlut.blue = drm_color_lut_extract(lut[i].blue, LUT_BITS_DEFAULT);
+		hwlut.red = drm_color_lut_extract(lut[i].red, gamma->data->lut_bits);
+		hwlut.green = drm_color_lut_extract(lut[i].green, gamma->data->lut_bits);
+		hwlut.blue = drm_color_lut_extract(lut[i].blue, gamma->data->lut_bits);
 
 		if (!gamma->data->lut_diff || (i % 2 == 0)) {
 			word = FIELD_PREP(DISP_GAMMA_LUT_10BIT_R, hwlut.red);
@@ -101,13 +102,13 @@ void mtk_gamma_set(struct device *dev, struct drm_crtc_state *state)
 			word |= FIELD_PREP(DISP_GAMMA_LUT_10BIT_B, hwlut.blue);
 		} else {
 			diff.red = lut[i].red - lut[i - 1].red;
-			diff.red = drm_color_lut_extract(diff.red, LUT_BITS_DEFAULT);
+			diff.red = drm_color_lut_extract(diff.red, gamma->data->lut_bits);
 
 			diff.green = lut[i].green - lut[i - 1].green;
-			diff.green = drm_color_lut_extract(diff.green, LUT_BITS_DEFAULT);
+			diff.green = drm_color_lut_extract(diff.green, gamma->data->lut_bits);
 
 			diff.blue = lut[i].blue - lut[i - 1].blue;
-			diff.blue = drm_color_lut_extract(diff.blue, LUT_BITS_DEFAULT);
+			diff.blue = drm_color_lut_extract(diff.blue, gamma->data->lut_bits);
 
 			word = FIELD_PREP(DISP_GAMMA_LUT_10BIT_R, diff.red);
 			word |= FIELD_PREP(DISP_GAMMA_LUT_10BIT_G, diff.green);
@@ -217,10 +218,12 @@ static int mtk_disp_gamma_remove(struct platform_device *pdev)
 
 static const struct mtk_disp_gamma_data mt8173_gamma_driver_data = {
 	.has_dither = true,
+	.lut_bits = 10,
 	.lut_size = 512,
 };
 
 static const struct mtk_disp_gamma_data mt8183_gamma_driver_data = {
+	.lut_bits = 10,
 	.lut_diff = true,
 	.lut_size = 512,
 };
-- 
2.41.0