[PATCH 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.delre...@collabora.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 3501c8b549be..ac7ab3863f6f 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
@@ -22,6 +22,7 @@
 #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)
@@ -88,6 +89,16 @@ 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);
@@ -181,6 +192,14 @@ 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