drm: sun4i: calculate proper DCLK rate for DSI

In DSI mode, TCON0's data clock is required to run at 1/4 the per-lane
bit rate.

Signed-off-by: Roman Beranek <me@crly.cz>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230505052110.67514-5-me@crly.cz

Author: Roman Beranek

drivers/gpu/drm/sun4i/sun4i_tcon.c

@@ -291,18 +291,6 @@ static int sun4i_tcon_get_clk_delay(const struct drm_display_mode *mode,
 	return delay;
 }
 
-static void sun4i_tcon0_mode_set_common(struct sun4i_tcon *tcon,
-					const struct drm_display_mode *mode)
-{
-	/* Configure the dot clock */
-	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
-
-	/* Set the resolution */
-	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
-		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
-		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
-}
-
 static void sun4i_tcon0_mode_set_dithering(struct sun4i_tcon *tcon,
 					   const struct drm_connector *connector)
 {
@@ -367,10 +355,18 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	u32 block_space, start_delay;
 	u32 tcon_div;
 
+	/*
+	 * dclk is required to run at 1/4 the DSI per-lane bit rate.
+	 */
 	tcon->dclk_min_div = SUN6I_DSI_TCON_DIV;
 	tcon->dclk_max_div = SUN6I_DSI_TCON_DIV;
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000 * (bpp / lanes)
+						  / SUN6I_DSI_TCON_DIV);
 
-	sun4i_tcon0_mode_set_common(tcon, mode);
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -438,7 +434,12 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 
 	tcon->dclk_min_div = 7;
 	tcon->dclk_max_div = 7;
-	sun4i_tcon0_mode_set_common(tcon, mode);
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -515,7 +516,12 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 
 	tcon->dclk_min_div = tcon->quirks->dclk_min_div;
 	tcon->dclk_max_div = 127;
-	sun4i_tcon0_mode_set_common(tcon, mode);
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, connector);