[RESEND,v6,04/11] drm/mediatek: gamma: Improve and simplify HW LUT calculation

Commit Message

AngeloGioacchino Del Regno July 27, 2023, 9:46 a.m. UTC

Use drm_color_lut_extract() to avoid open-coding the bits reduction
calculations for each color channel and use a struct drm_color_lut
to temporarily store the information instead of an array of u32.

Also, slightly improve the precision of the HW LUT calculation in the
LUT DIFF case by performing the subtractions on the 16-bits values and
doing the 10 bits conversion later.

Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>
Reviewed-by: Jason-JH.Lin <[e-mail]>
---
 drivers/gpu/drm/mediatek/mtk_disp_gamma.c | 30 +++++++++++++++--------
 1 file changed, 20 insertions(+), 10 deletions(-)

Comments

Alexandre Mergnat July 28, 2023, 1 p.m. UTC | #1

Reviewed-by: Alexandre Mergnat <[e-mail]>

On 27/07/2023 11:46, AngeloGioacchino Del Regno wrote:
> Use drm_color_lut_extract() to avoid open-coding the bits reduction
> calculations for each color channel and use a struct drm_color_lut
> to temporarily store the information instead of an array of u32.
> 
> Also, slightly improve the precision of the HW LUT calculation in the
> LUT DIFF case by performing the subtractions on the 16-bits values and
> doing the 10 bits conversion later.

Patch

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
index b25ba209e7a4..204a1aa7bfc9 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
@@ -77,7 +77,6 @@  void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crt
 	bool lut_diff;
 	u16 lut_size;
 	u32 word;
-	u32 diff[3] = {0};
 
 	/* If there's no gamma lut there's nothing to do here. */
 	if (!state->gamma_lut)
@@ -97,18 +96,29 @@  void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crt
 	lut_base = regs + DISP_GAMMA_LUT;
 	lut = (struct drm_color_lut *)state->gamma_lut->data;
 	for (i = 0; i < lut_size; i++) {
+		struct drm_color_lut diff, hwlut;
+
+		hwlut.red = drm_color_lut_extract(lut[i].red, 10);
+		hwlut.green = drm_color_lut_extract(lut[i].green, 10);
+		hwlut.blue = drm_color_lut_extract(lut[i].blue, 10);
+
 		if (!lut_diff || (i % 2 == 0)) {
-			word = (((lut[i].red >> 6) & LUT_10BIT_MASK) << 20) +
-				(((lut[i].green >> 6) & LUT_10BIT_MASK) << 10) +
-				((lut[i].blue >> 6) & LUT_10BIT_MASK);
+			word = hwlut.red << 20 +
+			       hwlut.green << 10 +
+			       hwlut.red;
 		} else {
-			diff[0] = (lut[i].red >> 6) - (lut[i - 1].red >> 6);
-			diff[1] = (lut[i].green >> 6) - (lut[i - 1].green >> 6);
-			diff[2] = (lut[i].blue >> 6) - (lut[i - 1].blue >> 6);
+			diff.red = lut[i].red - lut[i - 1].red;
+			diff.red = drm_color_lut_extract(diff.red, 10);
+
+			diff.green = lut[i].green - lut[i - 1].green;
+			diff.green = drm_color_lut_extract(diff.green, 10);
+
+			diff.blue = lut[i].blue - lut[i - 1].blue;
+			diff.blue = drm_color_lut_extract(diff.blue, 10);
 
-			word = ((diff[0] & LUT_10BIT_MASK) << 20) +
-				((diff[1] & LUT_10BIT_MASK) << 10) +
-				(diff[2] & LUT_10BIT_MASK);
+			word = diff.blue << 20 +
+			       diff.green << 10 +
+			       diff.red;
 		}
 		writel(word, (lut_base + i * 4));
 	}