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

[Arun Raghavan <arunr@valvesoftware.com>]

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 <arunr@valvesoftware.com>
>> Cc: Arun Raghavan <arun@arunraghavan.net>
>
> 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.

Cheers,
Arun