Hi,
On Tue, Sep 08, 2026 at 03:02:20PM +0800, Frank Zhang wrote:
> The following panic was observed during system reboot:
>
> Kernel panic - not syncing: Asynchronous SError Interrupt
> CPU: 6 UID: 1000 PID: 2348 Comm: pipewire ... 7.0.5+ #4 PREEMPT(full)
> Call trace:
> ...
> regmap_update_bits_base+0x70/0xa8
> dw_hdmi_qp_bridge_clear_audio_infoframe+0x3c/0x58 [dw_hdmi_qp]
> drm_bridge_connector_clear_audio_infoframe+0x2c/0x48 [drm_display_helper]
> ...
> dw_hdmi_qp_audio_disable+0x28/0xa8 [dw_hdmi_qp]
> drm_bridge_connector_audio_shutdown+0x38/0x68 [drm_display_helper]
> drm_connector_hdmi_audio_shutdown+0x28/0x40 [drm_display_helper]
> hdmi_codec_shutdown+0x60/0x90 [snd_soc_hdmi_codec]
> ...
> snd_pcm_release_substream+0xcc/0x120 [snd_pcm]
> snd_pcm_release+0x4c/0xc0 [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 disables the PHY.
>
> In this case, dw_hdmi_qp_audio_disable() will call
> dw_hdmi_qp_bridge_clear_audio_infoframe(), accessing register without
> checking tmds_char_rate.
>
> Guard the register access in drm_display_helper callback function with
> tmds_char_rate check.
>
> Fixes: fd0141d1a8a2 ("drm/bridge: synopsys: Add audio support for dw-hdmi-qp")
> Cc: [email protected]
> Signed-off-by: Frank Zhang <[email protected]>
>
> ---
> Changes in v2:
> - Move drm_atomic_helper_connector_hdmi_clear_audio_infoframe() inside
> the if (hdmi->tmds_char_rate) of dw_hdmi_qp_audio_disable().
> - Link to v1:
> https://lore.kernel.org/all/[email protected]/
>
> Changes in v3:
> - Add a tmds_char_rate guard in clear_audio_infoframe path.
> - Decouple write_audio_infoframe from clear_audio_infoframe.
> - Balance the PKTSCHED_AMD_TX_EN bit enable/disable.
> - Link to v2:
> https://lore.kernel.org/all/[email protected]/
>
> Changes in v4:
> - Update panic stack on 7.0.5
> - Link to v3:
> https://lore.kernel.org/all/[email protected]/
>
> Changes in v5:
> - Reuse the origin dw_hdmi_qp_bridge_clear_audio_infoframe and add
> tmds_char_rate guard in new callback function.
> - Link to v4:
> https://lore.kernel.org/all/[email protected]/
> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> index 1c214a8e6dc2..8729783d4eb6 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> @@ -880,7 +880,7 @@ static int dw_hdmi_qp_bridge_clear_spd_infoframe(struct
> drm_bridge *bridge)
> return 0;
> }
>
> -static int dw_hdmi_qp_bridge_clear_audio_infoframe(struct drm_bridge *bridge)
> +static int __dw_hdmi_qp_bridge_clear_audio_infoframe(struct drm_bridge
> *bridge)
> {
> struct dw_hdmi_qp *hdmi = bridge->driver_private;
>
> @@ -893,6 +893,16 @@ static int
> dw_hdmi_qp_bridge_clear_audio_infoframe(struct drm_bridge *bridge)
> return 0;
> }
>
> +static int dw_hdmi_qp_bridge_clear_audio_infoframe(struct drm_bridge *bridge)
> +{
> + struct dw_hdmi_qp *hdmi = bridge->driver_private;
> +
> + if (hdmi->tmds_char_rate > 0)
> + return __dw_hdmi_qp_bridge_clear_audio_infoframe(bridge);
> +
> + return 0;
> +}
> +
> static void dw_hdmi_qp_write_pkt(struct dw_hdmi_qp *hdmi, const u8 *buffer,
> size_t start, size_t len, unsigned int reg)
> {
> @@ -987,7 +997,7 @@ static int dw_hdmi_qp_bridge_write_audio_infoframe(struct
> drm_bridge *bridge,
> {
> struct dw_hdmi_qp *hdmi = bridge->driver_private;
>
> - dw_hdmi_qp_bridge_clear_audio_infoframe(bridge);
> + __dw_hdmi_qp_bridge_clear_audio_infoframe(bridge);
Why? Having the extra tmds_char_rate check being done here is not a
problem except for some extra instructions. Considering this is
definetly not a hot path, introducing the extra function is not
worth the trouble. Just patch the original function to add the check
resulting in a nice and simple 2 lines fix and you are done.
>
> /*
> * AUDI_CONTENTS0: { RSV, HB2, HB1, RSV }
> --
> 2.55.0
>
Greetings,
-- Sebastian
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