[PATCH v4 11/11] drm/mediatek: gamma: Program gamma LUT type for descending or rising

[AngeloGioacchino Del Regno]

All of the SoCs that don't have dithering control in the gamma IP
have got a GAMMA_LUT_TYPE bit that tells to the IP if the LUT is
"descending" (bit set) or "rising" (bit cleared): make sure to set
it correctly after programming the LUT.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Reviewed-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
index ba8a0f93f184..d7c7c6ca2e97 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
@@ -23,6 +23,7 @@
 #define GAMMA_RELAY_MODE				BIT(0)
 #define GAMMA_LUT_EN					BIT(1)
 #define GAMMA_DITHERING					BIT(2)
+#define GAMMA_LUT_TYPE					BIT(2)
 #define DISP_GAMMA_SIZE				0x0030
 #define DISP_GAMMA_SIZE_HSIZE				GENMASK(28, 16)
 #define DISP_GAMMA_SIZE_VSIZE				GENMASK(12, 0)
@@ -89,6 +90,16 @@ unsigned int mtk_gamma_get_lut_size(struct device *dev)
 	return lut_size;
 }
 
+static bool mtk_gamma_lut_is_descending(struct drm_color_lut *lut, u32 lut_size)
+{
+	u64 first, last;
+
+	first = lut[0].red + lut[0].green + lut[0].blue;
+	last = lut[lut_size].red + lut[lut_size].green + lut[lut_size].blue;
+
+	return !!(first > last);
+}
+
 void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crtc_state *state)
 {
 	struct mtk_disp_gamma *gamma = dev_get_drvdata(dev);
@@ -182,6 +193,14 @@ void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crt
 		}
 	}
 
+	if (gamma && !gamma->data->has_dither) {
+		/* Descending or Rising LUT */
+		if (mtk_gamma_lut_is_descending(lut, lut_size))
+			cfg_val |= FIELD_PREP(GAMMA_LUT_TYPE, 1);
+		else
+			cfg_val &= ~GAMMA_LUT_TYPE;
+	}
+
 	/* Enable the gamma table */
 	cfg_val |= FIELD_PREP(GAMMA_LUT_EN, 1);
 
-- 
2.40.1