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Message-ID: <20150611011236.53bcd1fd@mdontu-l>
Date: Thu, 11 Jun 2015 01:12:36 +0300
From: Mihai Donțu <mihai.dontu@...il.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: Jonathan McDowell <noodles@...th.li>, alsa-devel@...a-project.org,
linux-kernel@...r.kernel.org
Subject: Re: Audio crackles with 4.1-rc1
On Wed, 10 Jun 2015 20:23:01 +0200 Takashi Iwai wrote:
> From: Takashi Iwai <tiwai@...e.de>
> Subject: [PATCH] ALSA: hda - Reduce click noise at power up
>
> Some machines suffer from click noises at power up with the recent
> kernels, and this seems triggered at the power transition and the
> immediate verb executions. As a workaround, put a short delay (10ms)
> right after the D0 transition.
>
> There are a few places that have the same kind of delays, especially
> in the resume path. I guess they can be removed (or reduced) after
> this patch. But, since the delay is relatively small, let's do it
> later as a cleanup.
>
> Reported-by: Mihai Donțu <mihai.dontu@...il.com>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
> sound/pci/hda/hda_codec.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index b7782212dd64..38f5509ee52f 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -3077,6 +3077,9 @@ static unsigned int hda_set_power_state(struct hda_codec *codec,
> break;
> }
>
> + if (power_state == AC_PWRST_D0)
> + msleep(10);
> +
> return state;
> }
>
I take back my previous observations. I was at work and did not have
access to headphones (one of those days). Now I'm at home, it's 1 AM,
very quiet, and I notice the following:
* on speakers: the click reproduces but with _very_ low amplitude;
msleep(100) is unnoticeable, but msleep(10) is, barely;
* on headphones: the moment I plug them I hear a loud static sound
(like an old, untuned AM radio). If I play something, the static
disappears. If I pause, the static returns after ~15s.
--
Mihai Donțu
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