drm/sun4i: dw-hdmi: Add quirk for setting TMDS clock

It turns out that H6 HDMI BSP kernel driver doesn't change TMDS rate at
all. At this point it is not clear whether it is just not necessary or
it would cause some kind of issues.

Add a quirk for it.
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181104182705.18047-18-jernej.skrabec@siol.net

drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c

@@ -21,7 +21,8 @@ static void sun8i_dw_hdmi_encoder_mode_set(struct drm_encoder *encoder,
 {
 	struct sun8i_dw_hdmi *hdmi = encoder_to_sun8i_dw_hdmi(encoder);
 
-	clk_set_rate(hdmi->clk_tmds, mode->crtc_clock * 1000);
+	if (hdmi->quirks->set_rate)
+		clk_set_rate(hdmi->clk_tmds, mode->crtc_clock * 1000);
 }
 
 static const struct drm_encoder_helper_funcs
@@ -235,6 +236,7 @@ static int sun8i_dw_hdmi_remove(struct platform_device *pdev)
 
 static const struct sun8i_dw_hdmi_quirks sun8i_a83t_quirks = {
 	.mode_valid = sun8i_dw_hdmi_mode_valid_a83t,
+	.set_rate = true,
 };
 
 static const struct of_device_id sun8i_dw_hdmi_dt_ids[] = {

drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h

@@ -173,6 +173,7 @@ struct sun8i_hdmi_phy {
 struct sun8i_dw_hdmi_quirks {
 	enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
 					   const struct drm_display_mode *mode);
+	unsigned int set_rate : 1;
 };
 
 struct sun8i_dw_hdmi {