[PATCH] drm/bridge: dw-hdmi-qp: Guard clear_audio_infoframe when PHY is down

[Frank Zhang <rmxpzlb@gmail.com>]

The following panic was observed during system reboot:

Kernel panic - not syncing: Asynchronous SError Interrupt
CPU: 7 UID: 1000 PID: 2637 Comm: pipewire ... 6.19.10-300.fc44.aarch64
Call trace:
 ...
 regmap_update_bits_base+0x5c/0x90
 dw_hdmi_qp_bridge_clear_infoframe+0xb0/0x120 [dw_hdmi_qp]
 drm_bridge_connector_clear_infoframe+0x28/0x48 [drm_display_helper]
 ...
 dw_hdmi_qp_audio_disable+0x24/0xb8 [dw_hdmi_qp]
 drm_bridge_connector_audio_shutdown+0x30/0x60 [drm_display_helper]
 drm_connector_hdmi_audio_shutdown+0x24/0x38 [drm_display_helper]
 hdmi_codec_shutdown+0x60/0x90 [snd_soc_hdmi_codec]
 ...
 snd_pcm_release_substream.part.0+0x44/0xd8 [snd_pcm]
 snd_pcm_release+0x60/0xe8 [snd_pcm]
 ...

The root cause is pipewire tries to close the HDMI audio device after
atomic_disable(), which sets tmds_char_rate to 0 and disable the PHY.

In this case, dw_hdmi_qp_audio_disable() will call
clear_audio_infoframe(), accessing registers without checking
tmds_char_rate.

Add a tmds_char_rate check in dw_hdmi_qp_bridge_clear_audio_infoframe()
to skip the register write when the PHY is inactive.

Signed-off-by: Frank Zhang <rmxpzlb@gmail.com>

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
index d649a1cf07f5..f963dff81dc6 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
@@ -886,11 +886,12 @@ static int dw_hdmi_qp_bridge_clear_audio_infoframe(struct drm_bridge *bridge)
 {
 	struct dw_hdmi_qp *hdmi = bridge->driver_private;
 
-	dw_hdmi_qp_mod(hdmi, 0,
-		       PKTSCHED_ACR_TX_EN |
-		       PKTSCHED_AUDS_TX_EN |
-		       PKTSCHED_AUDI_TX_EN,
-		       PKTSCHED_PKT_EN);
+	if (hdmi->tmds_char_rate)
+		dw_hdmi_qp_mod(hdmi, 0,
+			       PKTSCHED_ACR_TX_EN |
+			       PKTSCHED_AUDS_TX_EN |
+			       PKTSCHED_AUDI_TX_EN,
+			       PKTSCHED_PKT_EN);
 
 	return 0;
 }
-- 
2.53.0