drm/mediatek: gamma: Reduce indentation in mtk_gamma_set_common()

Invert the check for state->gamma_lut and move it at the beginning
of the function to reduce indentation: this prepares the code for
keeping readability on later additions.

This commit brings no functional changes.

Reviewed-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20231012095736.100784-3-angelogioacchino.delregno@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: AngeloGioacchino Del Regno

drivers/gpu/drm/mediatek/mtk_disp_gamma.c

@@ -64,6 +64,10 @@ void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crt
 	u32 word;
 	u32 diff[3] = {0};
 
+	/* If there's no gamma lut there's nothing to do here. */
+	if (!state->gamma_lut)
+		return;
+
 	/* If we're called from AAL, dev is NULL */
 	gamma = dev ? dev_get_drvdata(dev) : NULL;
 
@@ -72,29 +76,26 @@ void mtk_gamma_set_common(struct device *dev, void __iomem *regs, struct drm_crt
 	else
 		lut_diff = false;
 
-	if (state->gamma_lut) {
-		reg = readl(regs + DISP_GAMMA_CFG);
-		reg = reg | GAMMA_LUT_EN;
-		writel(reg, regs + DISP_GAMMA_CFG);
-		lut_base = regs + DISP_GAMMA_LUT;
-		lut = (struct drm_color_lut *)state->gamma_lut->data;
-		for (i = 0; i < MTK_LUT_SIZE; i++) {
-
-			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);
-			} 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);
-
-				word = ((diff[0] & LUT_10BIT_MASK) << 20) +
-					((diff[1] & LUT_10BIT_MASK) << 10) +
-					(diff[2] & LUT_10BIT_MASK);
-			}
-			writel(word, (lut_base + i * 4));
+	reg = readl(regs + DISP_GAMMA_CFG);
+	reg = reg | GAMMA_LUT_EN;
+	writel(reg, regs + DISP_GAMMA_CFG);
+	lut_base = regs + DISP_GAMMA_LUT;
+	lut = (struct drm_color_lut *)state->gamma_lut->data;
+	for (i = 0; i < MTK_LUT_SIZE; i++) {
+		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);
+		} 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);
+
+			word = ((diff[0] & LUT_10BIT_MASK) << 20) +
+				((diff[1] & LUT_10BIT_MASK) << 10) +
+				(diff[2] & LUT_10BIT_MASK);
 		}
+		writel(word, (lut_base + i * 4));
 	}
 }