drm/mediatek: set mt8173 dithering function

Some panels only accept bpc (bit per color) 6-bit.
But, the default bpc in mt8173 display data path is 8-bit.
If we didn't enable dithering function to convert bpc,
display cannot show the smooth grayscale image.

In mt8173, the dithering function in OD (OverDrive) and
GAMMA module, we have to config them with
connector->display_mode.bpc when CRTC initial.

1. Clear the default value at *_DITHER_5 and *_DITHER_7 register.
2. Calculate the LSB_ERR_SHIFT bits and ADD_LSHIFT bits two values.
i.e. Input bpc of OD is 10 bits, we assume the bpc of panel is 6-bit,
so, we need to set 4-bit to LSB_ERR_SHIFT and ADD_LSHIFT bits respectively.
3. Then, set the OD or GAMMA to dithering mode depends on path-1 or path-2.

Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/mediatek/mtk_disp_ovl.c

@@ -103,7 +103,8 @@ static void mtk_ovl_stop(struct mtk_ddp_comp *comp)
 }
 
 static void mtk_ovl_config(struct mtk_ddp_comp *comp, unsigned int w,
-			   unsigned int h, unsigned int vrefresh)
+			   unsigned int h, unsigned int vrefresh,
+			   unsigned int bpc)
 {
 	if (w != 0 && h != 0)
 		writel_relaxed(h << 16 | w, comp->regs + DISP_REG_OVL_ROI_SIZE);

drivers/gpu/drm/mediatek/mtk_disp_rdma.c

@@ -106,7 +106,8 @@ static void mtk_rdma_stop(struct mtk_ddp_comp *comp)
 }
 
 static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
-			    unsigned int height, unsigned int vrefresh)
+			    unsigned int height, unsigned int vrefresh,
+			    unsigned int bpc)
 {
 	unsigned int threshold;
 	unsigned int reg;

drivers/gpu/drm/mediatek/mtk_drm_crtc.c

@@ -222,7 +222,9 @@ static void mtk_crtc_ddp_clk_disable(struct mtk_drm_crtc *mtk_crtc)
 static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc)
 {
 	struct drm_crtc *crtc = &mtk_crtc->base;
-	unsigned int width, height, vrefresh;
+	struct drm_connector *connector;
+	struct drm_encoder *encoder;
+	unsigned int width, height, vrefresh, bpc = MTK_MAX_BPC;
 	int ret;
 	int i;
 
@@ -234,6 +236,19 @@ static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc)
 	height = crtc->state->adjusted_mode.vdisplay;
 	vrefresh = crtc->state->adjusted_mode.vrefresh;
 
+	drm_for_each_encoder(encoder, crtc->dev) {
+		if (encoder->crtc != crtc)
+			continue;
+
+		drm_for_each_connector(connector, crtc->dev) {
+			if (connector->encoder != encoder)
+				continue;
+			if (connector->display_info.bpc != 0 &&
+			    bpc > connector->display_info.bpc)
+				bpc = connector->display_info.bpc;
+		}
+	}
+
 	ret = pm_runtime_get_sync(crtc->dev->dev);
 	if (ret < 0) {
 		DRM_ERROR("Failed to enable power domain: %d\n", ret);
@@ -266,7 +281,7 @@ static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc)
 	for (i = 0; i < mtk_crtc->ddp_comp_nr; i++) {
 		struct mtk_ddp_comp *comp = mtk_crtc->ddp_comp[i];
 
-		mtk_ddp_comp_config(comp, width, height, vrefresh);
+		mtk_ddp_comp_config(comp, width, height, vrefresh, bpc);
 		mtk_ddp_comp_start(comp);
 	}
 
@@ -468,7 +483,7 @@ void mtk_crtc_ddp_irq(struct drm_crtc *crtc, struct mtk_ddp_comp *ovl)
 	if (state->pending_config) {
 		mtk_ddp_comp_config(ovl, state->pending_width,
 				    state->pending_height,
-				    state->pending_vrefresh);
+				    state->pending_vrefresh, 0);
 
 		state->pending_config = false;
 	}

drivers/gpu/drm/mediatek/mtk_drm_crtc.h

@@ -20,6 +20,8 @@
 
 #define OVL_LAYER_NR	4
 #define MTK_LUT_SIZE	512
+#define MTK_MAX_BPC	10
+#define MTK_MIN_BPC	3
 
 int mtk_drm_crtc_enable_vblank(struct drm_device *drm, unsigned int pipe);
 void mtk_drm_crtc_disable_vblank(struct drm_device *drm, unsigned int pipe);

drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c

@@ -31,6 +31,10 @@
 #define DISP_OD_INTSTA				0x000c
 #define DISP_OD_CFG				0x0020
 #define DISP_OD_SIZE				0x0030
+#define DISP_DITHER_5				0x0114
+#define DISP_DITHER_7				0x011c
+#define DISP_DITHER_15				0x013c
+#define DISP_DITHER_16				0x0140
 
 #define DISP_REG_UFO_START			0x0000
 
@@ -49,20 +53,59 @@
 
 #define LUT_10BIT_MASK				0x03ff
 
-#define	OD_RELAY_MODE		BIT(0)
+#define COLOR_BYPASS_ALL			BIT(7)
+#define COLOR_SEQ_SEL				BIT(13)
 
-#define	UFO_BYPASS		BIT(2)
+#define OD_RELAYMODE				BIT(0)
 
-#define	COLOR_BYPASS_ALL	BIT(7)
-#define	COLOR_SEQ_SEL		BIT(13)
+#define UFO_BYPASS				BIT(2)
 
-#define AAL_EN			BIT(0)
+#define AAL_EN					BIT(0)
 
-#define GAMMA_EN		BIT(0)
-#define GAMMA_LUT_EN		BIT(1)
+#define GAMMA_EN				BIT(0)
+#define GAMMA_LUT_EN				BIT(1)
+
+#define DISP_DITHERING				BIT(2)
+#define DITHER_LSB_ERR_SHIFT_R(x)		(((x) & 0x7) << 28)
+#define DITHER_OVFLW_BIT_R(x)			(((x) & 0x7) << 24)
+#define DITHER_ADD_LSHIFT_R(x)			(((x) & 0x7) << 20)
+#define DITHER_ADD_RSHIFT_R(x)			(((x) & 0x7) << 16)
+#define DITHER_NEW_BIT_MODE			BIT(0)
+#define DITHER_LSB_ERR_SHIFT_B(x)		(((x) & 0x7) << 28)
+#define DITHER_OVFLW_BIT_B(x)			(((x) & 0x7) << 24)
+#define DITHER_ADD_LSHIFT_B(x)			(((x) & 0x7) << 20)
+#define DITHER_ADD_RSHIFT_B(x)			(((x) & 0x7) << 16)
+#define DITHER_LSB_ERR_SHIFT_G(x)		(((x) & 0x7) << 12)
+#define DITHER_OVFLW_BIT_G(x)			(((x) & 0x7) << 8)
+#define DITHER_ADD_LSHIFT_G(x)			(((x) & 0x7) << 4)
+#define DITHER_ADD_RSHIFT_G(x)			(((x) & 0x7) << 0)
+
+void mtk_dither_set(struct mtk_ddp_comp *comp, unsigned int bpc,
+		    unsigned int CFG)
+{
+	/* If bpc equal to 0, the dithering function didn't be enabled */
+	if (bpc == 0)
+		return;
+
+	if (bpc >= MTK_MIN_BPC) {
+		writel(0, comp->regs + DISP_DITHER_5);
+		writel(0, comp->regs + DISP_DITHER_7);
+		writel(DITHER_LSB_ERR_SHIFT_R(MTK_MAX_BPC - bpc) |
+		       DITHER_ADD_LSHIFT_R(MTK_MAX_BPC - bpc) |
+		       DITHER_NEW_BIT_MODE,
+		       comp->regs + DISP_DITHER_15);
+		writel(DITHER_LSB_ERR_SHIFT_B(MTK_MAX_BPC - bpc) |
+		       DITHER_ADD_LSHIFT_B(MTK_MAX_BPC - bpc) |
+		       DITHER_LSB_ERR_SHIFT_G(MTK_MAX_BPC - bpc) |
+		       DITHER_ADD_LSHIFT_G(MTK_MAX_BPC - bpc),
+		       comp->regs + DISP_DITHER_16);
+		writel(DISP_DITHERING, comp->regs + CFG);
+	}
+}
 
 static void mtk_color_config(struct mtk_ddp_comp *comp, unsigned int w,
-			     unsigned int h, unsigned int vrefresh)
+			     unsigned int h, unsigned int vrefresh,
+			     unsigned int bpc)
 {
 	writel(w, comp->regs + DISP_COLOR_WIDTH);
 	writel(h, comp->regs + DISP_COLOR_HEIGHT);
@@ -76,14 +119,16 @@ static void mtk_color_start(struct mtk_ddp_comp *comp)
 }
 
 static void mtk_od_config(struct mtk_ddp_comp *comp, unsigned int w,
-			  unsigned int h, unsigned int vrefresh)
+			  unsigned int h, unsigned int vrefresh,
+			  unsigned int bpc)
 {
 	writel(w << 16 | h, comp->regs + DISP_OD_SIZE);
+	writel(OD_RELAYMODE, comp->regs + OD_RELAYMODE);
+	mtk_dither_set(comp, bpc, DISP_OD_CFG);
 }
 
 static void mtk_od_start(struct mtk_ddp_comp *comp)
 {
-	writel(OD_RELAY_MODE, comp->regs + DISP_OD_CFG);
 	writel(1, comp->regs + DISP_OD_EN);
 }
 
@@ -93,7 +138,8 @@ static void mtk_ufoe_start(struct mtk_ddp_comp *comp)
 }
 
 static void mtk_aal_config(struct mtk_ddp_comp *comp, unsigned int w,
-			   unsigned int h, unsigned int vrefresh)
+			   unsigned int h, unsigned int vrefresh,
+			   unsigned int bpc)
 {
 	writel(h << 16 | w, comp->regs + DISP_AAL_SIZE);
 }
@@ -109,9 +155,11 @@ static void mtk_aal_stop(struct mtk_ddp_comp *comp)
 }
 
 static void mtk_gamma_config(struct mtk_ddp_comp *comp, unsigned int w,
-			     unsigned int h, unsigned int vrefresh)
+			     unsigned int h, unsigned int vrefresh,
+			     unsigned int bpc)
 {
 	writel(h << 16 | w, comp->regs + DISP_GAMMA_SIZE);
+	mtk_dither_set(comp, bpc, DISP_GAMMA_CFG);
 }
 
 static void mtk_gamma_start(struct mtk_ddp_comp *comp)

drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h

@@ -65,7 +65,7 @@ struct mtk_ddp_comp;
 
 struct mtk_ddp_comp_funcs {
 	void (*config)(struct mtk_ddp_comp *comp, unsigned int w,
-		       unsigned int h, unsigned int vrefresh);
+		       unsigned int h, unsigned int vrefresh, unsigned int bpc);
 	void (*start)(struct mtk_ddp_comp *comp);
 	void (*stop)(struct mtk_ddp_comp *comp);
 	void (*enable_vblank)(struct mtk_ddp_comp *comp, struct drm_crtc *crtc);
@@ -89,10 +89,10 @@ struct mtk_ddp_comp {
 
 static inline void mtk_ddp_comp_config(struct mtk_ddp_comp *comp,
 				       unsigned int w, unsigned int h,
-				       unsigned int vrefresh)
+				       unsigned int vrefresh, unsigned int bpc)
 {
 	if (comp->funcs && comp->funcs->config)
-		comp->funcs->config(comp, w, h, vrefresh);
+		comp->funcs->config(comp, w, h, vrefresh, bpc);
 }
 
 static inline void mtk_ddp_comp_start(struct mtk_ddp_comp *comp)
@@ -156,5 +156,7 @@ int mtk_ddp_comp_init(struct device *dev, struct device_node *comp_node,
 		      const struct mtk_ddp_comp_funcs *funcs);
 int mtk_ddp_comp_register(struct drm_device *drm, struct mtk_ddp_comp *comp);
 void mtk_ddp_comp_unregister(struct drm_device *drm, struct mtk_ddp_comp *comp);
+void mtk_dither_set(struct mtk_ddp_comp *comp, unsigned int bpc,
+		    unsigned int CFG);
 
 #endif /* MTK_DRM_DDP_COMP_H */