drm/vc4: hdmi: Limit the BCM2711 to the max without scrambling

Unlike the previous generations, the HSM clock limitation is way above
what we can reach without scrambling, so let's move the maximum
frequency we support to the maximum clock frequency without scrambling.
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215154243.540115-9-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -82,6 +82,8 @@
 #define CEC_CLOCK_FREQ 40000
 #define VC4_HSM_MID_CLOCK 149985000
 
+#define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
+
 static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
 {
 	struct drm_info_node *node = (struct drm_info_node *)m->private;
@@ -1918,7 +1920,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi0_variant = {
 	.encoder_type		= VC4_ENCODER_TYPE_HDMI0,
 	.debugfs_name		= "hdmi0_regs",
 	.card_name		= "vc4-hdmi-0",
-	.max_pixel_clock	= 297000000,
+	.max_pixel_clock	= HDMI_14_MAX_TMDS_CLK,
 	.registers		= vc5_hdmi_hdmi0_fields,
 	.num_registers		= ARRAY_SIZE(vc5_hdmi_hdmi0_fields),
 	.phy_lane_mapping	= {
@@ -1944,7 +1946,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi1_variant = {
 	.encoder_type		= VC4_ENCODER_TYPE_HDMI1,
 	.debugfs_name		= "hdmi1_regs",
 	.card_name		= "vc4-hdmi-1",
-	.max_pixel_clock	= 297000000,
+	.max_pixel_clock	= HDMI_14_MAX_TMDS_CLK,
 	.registers		= vc5_hdmi_hdmi1_fields,
 	.num_registers		= ARRAY_SIZE(vc5_hdmi_hdmi1_fields),
 	.phy_lane_mapping	= {