drm/vc4: hdmi: Don't try disabling SCDC on Pi0-3.

The code that set the scdc_enabled flag to ensure it was
disabled at boot time also ran on Pi0-3 where there is no
SCDC support. This lead to a warning in vc4_hdmi_encoder_post_crtc_disable
due to vc4_hdmi_disable_scrambling being called and trying to
read (and write) register HDMI_SCRAMBLER_CTL which doesn't
exist on those platforms.

Only set the flag should the interface be configured to support
more than HDMI 1.4.

Fixes: 1998646 ("drm/vc4: hdmi: Introduce a scdc_enabled flag")
Signed-off-by: Dave Stevenson <[email protected]>
Signed-off-by: Maxime Ripard <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: 6by9

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -2510,7 +2510,8 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 	 * vc4_hdmi_disable_scrambling() will thus run at boot, make
 	 * sure it's disabled, and avoid any inconsistency.
 	 */
-	vc4_hdmi->scdc_enabled = true;
+	if (variant->max_pixel_clock > HDMI_14_MAX_TMDS_CLK)
+		vc4_hdmi->scdc_enabled = true;
 
 	ret = variant->init_resources(vc4_hdmi);
 	if (ret)