Re: [External Mail] Re: [PATCH] ALSA: hda/core: Log stream DMA errors on interrupt

On Wed Aug 5, 2026 at 11:30 PM PDT, Takashi Iwai wrote:
> On Wed, 05 Aug 2026 22:56:40 +0200,
> Arun Raghavan wrote:
>> 
>> On Tue Aug 4, 2026 at 11:18 AM PDT, Takashi Iwai wrote:
>> > On Tue, 04 Aug 2026 19:42:17 +0200,
>> > Arun Raghavan wrote:
>> >> 
>> >> On Tue Aug 4, 2026 at 4:21 AM PDT, Takashi Iwai wrote:
>> >> > On Tue, 04 Aug 2026 00:07:52 +0200,
>> >> > Arun Raghavan wrote:
>> >> >> 
>> >> >> The stream descriptor status register reports FIFO and descriptor
>> >> >> errors, but these are currently cleared silently along with the rest
>> >> >> of the interrupt status. Log them, rate-limited, so DMA problems are
>> >> >> visible instead of only manifesting as audible glitches.
>> >> >> 
>> >> >> Observed on some AMD GPU HDMI audio controllers under specific low power
>> >> >> circumstances.
>> >> >> 
>> >> >> Signed-off-by: Arun Raghavan <[email protected]>
>> >> >> Cc: Arun Raghavan <[email protected]>
>> >> >
>> >> > Applied now to for-next branch.
>> >> >
>> >> > It's interesting at which situation you get the error bit and which
>> >> > one.  If it can be used *reliably* for catching a streaming error, the
>> >> > driver could notify XRUN or error appropriately, too.
>> >> 
>> >> Ah, I should have mentioned that in the commit message. The error bit
>> >> that was signalled was SD_INT_FIFO_ERR -- the status byte was read as
>> >> (SD_STS_FIFO_READY | SD_INT_FIFO_ERR).
>> >> 
>> >> We are still working on pinning down the precise cause in this case, but
>> >> it seems to be related to issues in some specific setups during lower
>> >> frequency memory clock transitions. The error manifests as a short
>> >> dropout caused by what appears to be a stall or missed transfer. The
>> >> frequency of dropouts varies from several per minute to one every few
>> >> minutes.
>> >> 
>> >> In such a case, the existence of XRUNs might be good to know further up
>> >> the stack, though it isn't clear that there is much that userspace can
>> >> autonomously do to mitigate the it.
>> >
>> > When we do stop the stream as XRUN and notifies to user-space, usually
>> > it tries to recover / restart -- something like below.
>> >
>> > But it's hard to judge whether we should do this, or it can lead
>> > rather to misbehavior.  We need experiments.
>> >
>> >
>> > thanks,
>> >
>> > Takashi
>> >
>> > -- 8< --
>> > diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
>> > index aa994d6e6d35..615e48ecb009 100644
>> > --- a/include/sound/hdaudio.h
>> > +++ b/include/sound/hdaudio.h
>> > @@ -412,7 +412,9 @@ void snd_hdac_bus_link_power(struct hdac_device *hdev, bool enable);
>> >  void snd_hdac_bus_update_rirb(struct hdac_bus *bus);
>> >  int snd_hdac_bus_handle_stream_irq(struct hdac_bus *bus, unsigned int status,
>> >  				    void (*ack)(struct hdac_bus *,
>> > -						struct hdac_stream *));
>> > +						struct hdac_stream *),
>> > +				    void (*error)(struct hdac_bus *,
>> > +						  struct hdac_stream *));
>> >  
>> >  int snd_hdac_bus_alloc_stream_pages(struct hdac_bus *bus);
>> >  void snd_hdac_bus_free_stream_pages(struct hdac_bus *bus);
>> > diff --git a/sound/hda/common/controller.c b/sound/hda/common/controller.c
>> > index afec5c5546ec..329854c9fe92 100644
>> > --- a/sound/hda/common/controller.c
>> > +++ b/sound/hda/common/controller.c
>> > @@ -1058,6 +1058,15 @@ static void stream_update(struct hdac_bus *bus, struct hdac_stream *s)
>> >  	}
>> >  }
>> >  
>> > +static void stream_error(struct hdac_bus *bus, struct hdac_stream *s)
>> > +{
>> > +	struct azx_dev *azx_dev = stream_to_azx_dev(s);
>> > +
>> > +	spin_unlock(&bus->reg_lock);
>> > +	snd_pcm_stop_xrun(azx_stream(azx_dev)->substream);
>> > +	spin_lock(&bus->reg_lock);
>> > +}
>> > +
>> >  irqreturn_t azx_interrupt(int irq, void *dev_id)
>> >  {
>> >  	struct azx *chip = dev_id;
>> > @@ -1082,7 +1091,8 @@ irqreturn_t azx_interrupt(int irq, void *dev_id)
>> >  
>> >  		handled = true;
>> >  		active = false;
>> > -		if (snd_hdac_bus_handle_stream_irq(bus, status, stream_update))
>> > +		if (snd_hdac_bus_handle_stream_irq(bus, status, stream_update,
>> > +						   stream_error))
>> >  			active = true;
>> >  
>> >  		status = azx_readb(chip, RIRBSTS);
>> > diff --git a/sound/hda/core/controller.c b/sound/hda/core/controller.c
>> > index 78855ac357c6..67bb74c618bf 100644
>> > --- a/sound/hda/core/controller.c
>> > +++ b/sound/hda/core/controller.c
>> > @@ -676,8 +676,10 @@ EXPORT_SYMBOL_GPL(snd_hdac_bus_stop_chip);
>> >   * Returns the bits of handled streams, or zero if no stream is handled.
>> >   */
>> >  int snd_hdac_bus_handle_stream_irq(struct hdac_bus *bus, unsigned int status,
>> > -				    void (*ack)(struct hdac_bus *,
>> > -						struct hdac_stream *))
>> > +				   void (*ack)(struct hdac_bus *,
>> > +					       struct hdac_stream *),
>> > +				   void (*error)(struct hdac_bus *,
>> > +						 struct hdac_stream *))
>> >  {
>> >  	struct hdac_stream *azx_dev;
>> >  	u8 sd_status;
>> > @@ -692,6 +694,8 @@ int snd_hdac_bus_handle_stream_irq(struct hdac_bus *bus, unsigned int status,
>> >  				dev_warn_ratelimited(bus->dev,
>> >  						"stream %u dma error: 0x%02x\n",
>> >  						azx_dev->index, sd_status);
>> > +				if (error)
>> > +					error(bus, azx_dev);
>> >  			}
>> >  			if ((!azx_dev->substream && !azx_dev->cstream) ||
>> >  			    !azx_dev->running || !(sd_status & SD_INT_COMPLETE))
>> > diff --git a/sound/soc/intel/avs/core.c b/sound/soc/intel/avs/core.c
>> > index 1a53856c2ffb..6a5a6e526c2c 100644
>> > --- a/sound/soc/intel/avs/core.c
>> > +++ b/sound/soc/intel/avs/core.c
>> > @@ -270,7 +270,8 @@ static irqreturn_t avs_hda_interrupt(struct hdac_bus *bus)
>> >  	u32 status;
>> >  
>> >  	status = snd_hdac_chip_readl(bus, INTSTS);
>> > -	if (snd_hdac_bus_handle_stream_irq(bus, status, hdac_update_stream))
>> > +	if (snd_hdac_bus_handle_stream_irq(bus, status, hdac_update_stream,
>> > +					   NULL))
>> >  		ret = IRQ_HANDLED;
>> >  
>> >  	spin_lock_irq(&bus->reg_lock);
>> 
>> This did work to surface the errors to userspace as XRUNs.
>> 
>> Of course, because this is an actual error in the transfer between the
>> CPU and controller, it does not help mitigate the actual problem itself.
>
> So what's the best option for users if this happens?
> That is, what happens if we don't restart the stream?  Is it a
> temporary fail-out and the hardware recovers / resync by itself while
> streaming further?  If so and it's short, it might be better to leave
> it as is.  OTOH, if it's a fatal error that needs some manual
> recovery, a notification to user-space for recovery is required (if
> any).

Unfortunately, there doesn't appear to be much users can do in this
state. The warnings we have introduced should at least point to a cause,
but the issues seem to be around GPU clocks and power management, for
example like in this issue:

  https://gitlab.freedesktop.org/drm/amd/-/work_items/4517

-- Arun