Re: [PATCH v2] drm/bridge: dw-hdmi-qp: Guard clear_audio_infoframe when PHY is down

[Dmitry Baryshkov]

On Mon, Apr 20, 2026 at 02:11:28PM +0800, Frank Zhang wrote:
> On 4/19/26 08:40, Dmitry Baryshkov wrote:
> > On Sat, Apr 18, 2026 at 06:19:36PM +0800, Frank Zhang wrote:
> > > 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
> > > drm_atomic_helper_connector_hdmi_clear_audio_infoframe() directly,
> > > accessing registers without checking tmds_char_rate.
> > > 
> > > Move drm_atomic_helper_connector_hdmi_clear_audio_infoframe() inside the
> > > if (hdmi->tmds_char_rate) of dw_hdmi_qp_audio_disable().
> > > 
> > > Fixes: fd0141d1a8a2 ("drm/bridge: synopsys: Add audio support for dw-hdmi-qp")
> > > Signed-off-by: Frank Zhang <rmxpzlb@xxxxxxxxx>
> > > 
> > > ---
> > > 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/20260416093150.13853-1-rmxpzlb@xxxxxxxxx/
> > > 
> > > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> > > index d649a1cf07f5..7760527484c8 100644
> > > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> > > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> > > @@ -526,10 +526,10 @@ static void dw_hdmi_qp_audio_disable(struct drm_bridge *bridge,
> > >   {
> > >   	struct dw_hdmi_qp *hdmi = dw_hdmi_qp_from_bridge(bridge);
> > > -	drm_atomic_helper_connector_hdmi_clear_audio_infoframe(connector);
> > > -
> > > -	if (hdmi->tmds_char_rate)
> > > +	if (hdmi->tmds_char_rate) {
> > > +		drm_atomic_helper_connector_hdmi_clear_audio_infoframe(connector);
> > >   		dw_hdmi_qp_audio_disable_regs(hdmi);
> > > +	}
> > 
> > Will audio and audio infoframe remain disabled after consequetive
> > atomic_enable() call?
> > 
> > >   }
> > >   static int dw_hdmi_qp_i2c_read(struct dw_hdmi_qp *hdmi,
> > > -- 
> > > 2.53.0
> > > 
> > 
> 
> Sorry, I missed clearing the audio infoframe when the PHY is down. The next
> atomic_enable() will write the stale audio infoframe. My mistake.
> 
> To clear the stale audio infoframe, dw_hdmi_qp_audio_disable() can handle it
> in the else branch directly, but this seems like a layering violation for a
> bridge driver
> 
> I think the better approach is to add a 'reset_audio_infoframe' interface in
> drm_hdmi_state_helper.c that does basically the same as
> drm_atomic_helper_connector_hdmi_clear_audio_infoframe(), but only clearing
> the software state without calling clear_infoframe(). It's also a bit odd
> since it would only be used by dw-hdmi-qp.

That sounds too fine-grained and it also will not work straight ahead...

Just for my understanding, let's consider the opposite situation: the
user tries to start audio playback before setting the mode. How is it
handled in the driver?

> 
> I'd like to get the maintainers' opinion about adding such an interface.
> 
> Thanks,
> Frank Zhang
> 

-- 
With best wishes
Dmitry