drm/vc4: hdmi: Ensure we don't use 2711 HPD registers on Pi0-3

The existing logic was flawed in that it could try reading the
2711 specific registers for HPD on a CM1/3 where the HPD GPIO
hadn't been defined in DT.

Ensure we don't do the 2711 register read on invalid hardware,
and then

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220127131754.236074-1-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -196,14 +196,8 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
 		if (gpiod_get_value_cansleep(vc4_hdmi->hpd_gpio))
 			connected = true;
 	} else {
-		unsigned long flags;
-		u32 hotplug;
-
-		spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
-		hotplug = HDMI_READ(HDMI_HOTPLUG);
-		spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
-
-		if (hotplug & VC4_HDMI_HOTPLUG_CONNECTED)
+		if (vc4_hdmi->variant->hp_detect &&
+		    vc4_hdmi->variant->hp_detect(vc4_hdmi))
 			connected = true;
 	}
 
@@ -1343,6 +1337,18 @@ static u32 vc5_hdmi_channel_map(struct vc4_hdmi *vc4_hdmi, u32 channel_mask)
 	return channel_map;
 }
 
+static bool vc5_hdmi_hp_detect(struct vc4_hdmi *vc4_hdmi)
+{
+	unsigned long flags;
+	u32 hotplug;
+
+	spin_lock_irqsave(&vc4_hdmi->hw_lock, flags);
+	hotplug = HDMI_READ(HDMI_HOTPLUG);
+	spin_unlock_irqrestore(&vc4_hdmi->hw_lock, flags);
+
+	return !!(hotplug & VC4_HDMI_HOTPLUG_CONNECTED);
+}
+
 /* HDMI audio codec callbacks */
 static void vc4_hdmi_audio_set_mai_clock(struct vc4_hdmi *vc4_hdmi,
 					 unsigned int samplerate)
@@ -2723,6 +2729,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi0_variant = {
 	.phy_rng_disable	= vc5_hdmi_phy_rng_disable,
 	.channel_map		= vc5_hdmi_channel_map,
 	.supports_hdr		= true,
+	.hp_detect		= vc5_hdmi_hp_detect,
 };
 
 static const struct vc4_hdmi_variant bcm2711_hdmi1_variant = {
@@ -2751,6 +2758,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi1_variant = {
 	.phy_rng_disable	= vc5_hdmi_phy_rng_disable,
 	.channel_map		= vc5_hdmi_channel_map,
 	.supports_hdr		= true,
+	.hp_detect		= vc5_hdmi_hp_detect,
 };
 
 static const struct of_device_id vc4_hdmi_dt_match[] = {

drivers/gpu/drm/vc4/vc4_hdmi.h

@@ -102,6 +102,9 @@ struct vc4_hdmi_variant {
 
 	/* Enables HDR metadata */
 	bool supports_hdr;
+
+	/* Callback for hardware specific hotplug detect */
+	bool (*hp_detect)(struct vc4_hdmi *vc4_hdmi);
 };
 
 /* HDMI audio information */