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From:   Jeff Chua <jeff.chua.linux@gmail.com>
Date:   Mon, 1 May 2023 23:05:27 +0800
Message-ID: <CAAJw_ZtKnZ3QruicqFRG_TLV0Ltbc8LSvdJSCEQRkr5GMSWvCw@mail.gmail.com>
Subject: Re: linux-6.4 alsa sound broken
To:     Oswald Buddenhagen <oswald.buddenhagen@gmx.de>,
        Jeff Chua <jeff.chua.linux@gmail.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Takashi Iwai <tiwai@suse.de>
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On Mon, May 1, 2023 at 3:17=E2=80=AFPM Oswald Buddenhagen
<oswald.buddenhagen@gmx.de> wrote:
>
> On Mon, May 01, 2023 at 11:59:12AM +0800, Jeff Chua wrote:
> >Latest git pull from Linus's tree ... playing a simple sound file will
> >resulted in a lot of echo.
> >
> how _exactly_ does it sound?
> have you recorded a file through loopback for us to investigate? best
> would be a short sample of a clean wave (sine or sawtooth) with some
> leading and trailing silence.

Just send .. in another email. If the atttachment got stripped off,
please let me know.


> >Running on Lenovo X1 with ..
> >00:1f.3 Audio device: Intel Corporation Alder Lake PCH-P High
> >Definition Audio Controller (rev 01)
> >
> >I've bisected and reverted the following patch fixed the problem.
> >
> this seems weird. so my first thought is: are you _sure_ that your
> bisect isn't "contaminated" somehow? is the effect consistent across
> several reboots with the same build? does re-applying my patch
> immediately re-introduce the problem?
>
> - this code is about silencing. getting dropouts or no playback at all
>    would be plausible, while echo (that is, repetition) seems surprising.
>    theoretically, the driver may be setting a bad fill_silence() callback
>    which copies some garbage instead of zeroing, but the HDA driver
>    doesn't set one at all (i.e., uses the default one).
> - this code must be explicitly enabled, which for all i know is done by
>    almost nothing. what players did you try? did you get consistent
>    results? did you try taking out audio servers from the equation?
> - the affected hardware belongs to the extremely widely used HDA family,
>    which at the layer the patch is even remotely connected with is
>    completely standardized. so _a lot_ of people should be affected, and
>    we should be getting reports like yours by the dozen. are we?
>
> of course i can't exclude the possibility that my patch is affected by
> an uninitialized variable or memory corruption (or in the worst case
> causes it), which would of course have very hard to predict effects. but
> that should be investigated properly instead of just reverting, lest we
> might be papering over a much more serious problem.
>
> -- ossi
>
> >commit 9f656705c5faa18afb26d922cfc64f9fd103c38d
> >Author: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
> >Date:   Thu Apr 20 13:33:23 2023 +0200
> >
> >    ALSA: pcm: rewrite snd_pcm_playback_silence()
> >
> >    The auto-silencer supports two modes: "thresholded" to fill up "just
> >    enough", and "top-up" to fill up "as much as possible". The two mode=
s
> >    used rather distinct code paths, which this patch unifies. The only
> >    remaining distinction is how much we actually want to fill.
> >
> >    This fixes a bug in thresholded mode, where we failed to use new_hw_=
ptr,
> >    resulting in under-fill.
> >
> >    Top-up mode is now more well-behaved and much easier to understand i=
n
> >    corner cases.
> >
> >    This also updates comments in the proximity of silencing-related dat=
a
> >    structures.
> >
> >    Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
> >    Reviewed-by: Jaroslav Kysela <perex@perex.cz>
> >    Link: https://lore.kernel.org/r/20230420113324.877164-1-oswald.budde=
nhagen@gmx.de
> >    Signed-off-by: Takashi Iwai <tiwai@suse.de>