drm/bridge: dw-hdmi: handle ELD when DRM_BRIDGE_ATTACH_NO_CONNECTOR

The current ELD handling takes the internal connector ELD buffer and
shares it to the I2S and AHB sub-driver.

But with DRM_BRIDGE_ATTACH_NO_CONNECTOR, the connector is created
elsewhere (or not), and an eventual connector is known only
if the bridge chain up to a connector is enabled.

The current dw-hdmi code gets the current connector from
atomic_enable() so use the already stored connector pointer and
replace the buffer pointer with a callback returning the current
connector ELD buffer.

Since a connector is not always available, either pass an empty
ELD to the alsa HDMI driver or don't call snd_pcm_hw_constraint_eld()
in AHB driver.

Reported-by: Martin Blumenstingl <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
[narmstrong: fixed typo in commit log]
Acked-by: Jernej Skrabec <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c

···
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct snd_dw_hdmi *dw = substream->private_data;
 	void __iomem *base = dw->data.base;
+	u8 *eld;
 	int ret;
 
 	runtime->hw = dw_hdmi_hw;
 
-	ret = snd_pcm_hw_constraint_eld(runtime, dw->data.eld);
-	if (ret < 0)
-		return ret;
+	eld = dw->data.get_eld(dw->data.hdmi);
+	if (eld) {
+		ret = snd_pcm_hw_constraint_eld(runtime, eld);
+		if (ret < 0)
+			return ret;
+	}
 
 	ret = snd_pcm_limit_hw_rates(runtime);
 	if (ret < 0)

drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h

···
 	void __iomem *base;
 	int irq;
 	struct dw_hdmi *hdmi;
-	u8 *eld;
+	u8 *(*get_eld)(struct dw_hdmi *hdmi);
 };
 
 struct dw_hdmi_i2s_audio_data {
 	struct dw_hdmi *hdmi;
-	u8 *eld;
 
 	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
 	u8 (*read)(struct dw_hdmi *hdmi, int offset);
+	u8 *(*get_eld)(struct dw_hdmi *hdmi);
 };
 
 #endif

drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c

···
 			       size_t len)
 {
 	struct dw_hdmi_i2s_audio_data *audio = data;
+	u8 *eld;
 
-	memcpy(buf, audio->eld, min_t(size_t, MAX_ELD_BYTES, len));
+	eld = audio->get_eld(audio->hdmi);
+	if (eld)
+		memcpy(buf, eld, min_t(size_t, MAX_ELD_BYTES, len));
+	else
+		/* Pass en empty ELD if connector not available */
+		memset(buf, 0, len);
+
 	return 0;
 }
 

drivers/gpu/drm/bridge/synopsys/dw-hdmi.c

···
 	hdmi_writeb(hdmi, hdmi->mc_clkdis, HDMI_MC_CLKDIS);
 }
 
+static u8 *hdmi_audio_get_eld(struct dw_hdmi *hdmi)
+{
+	if (!hdmi->curr_conn)
+		return NULL;
+
+	return hdmi->curr_conn->eld;
+}
+
 static void dw_hdmi_ahb_audio_enable(struct dw_hdmi *hdmi)
 {
 	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
···
 		audio.base = hdmi->regs;
 		audio.irq = irq;
 		audio.hdmi = hdmi;
-		audio.eld = hdmi->connector.eld;
+		audio.get_eld = hdmi_audio_get_eld;
 		hdmi->enable_audio = dw_hdmi_ahb_audio_enable;
 		hdmi->disable_audio = dw_hdmi_ahb_audio_disable;
 
···
 		struct dw_hdmi_i2s_audio_data audio;
 
 		audio.hdmi	= hdmi;
-		audio.eld	= hdmi->connector.eld;
+		audio.get_eld	= hdmi_audio_get_eld;
 		audio.write	= hdmi_writeb;
 		audio.read	= hdmi_readb;
 		hdmi->enable_audio = dw_hdmi_i2s_audio_enable;