From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: alsa-devel@alsa-project.org
Subject: Re: [PATCH 2/2] ALSA: hda: support for wallclock timestamps
Date: Wed, 13 Jun 2012 23:57:59 -0500 [thread overview]
Message-ID: <4FD96F57.3090502@linux.intel.com> (raw)
In-Reply-To: <CA+v+29goT9xmx-h4Fuiyg6wuZFCvBvuFx=1P_=e8CfqoQFahMA@mail.gmail.com>
On 6/13/2012 10:32 PM, Wang Xingchao wrote:
> I'm afraid you donot think much about the Wall Clock Counter register,
> the counter will roll over to 0 within 179s under 24Mhz. Another case
> maybe BCLK stop and controller reset. thanks --xingchao
Hi Xingchao,
all cycle counters will wrap around at some point, the HDAudio wall
clock isn't an exception. As long as you have 2 periods or events per
179s, the wrap-around can be detected without any issues. It's
explicitely handled in the code.
If the BCLK stops, then there's no real audio transfer happening, is
there? Likewise the controller reset does not matter since we re-init
during a trigger.
I don't see any of these points as show-stoppers. The HDAudio spec
clearly mentions that such a wall clock should be used for
synchronization with other devices, and I am enabling just that.
Regards,
-Pierre
next prev parent reply other threads:[~2012-06-14 4:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-13 20:26 [PATCH 0/2] RFC: support for audio wall clock Pierre-Louis Bossart
2012-06-13 20:26 ` [PATCH 1/2] ALSA: core: add hooks for audio timestamps read from WALLCLOCK Pierre-Louis Bossart
2012-06-14 7:27 ` Takashi Iwai
2012-06-15 10:07 ` Pierre-Louis Bossart
2012-06-13 20:26 ` [PATCH 2/2] ALSA: hda: support for wallclock timestamps Pierre-Louis Bossart
2012-06-14 3:32 ` Wang Xingchao
2012-06-14 4:57 ` Pierre-Louis Bossart [this message]
2012-06-14 8:15 ` Clemens Ladisch
2012-06-14 17:01 ` Pierre-Louis Bossart
2012-06-14 7:38 ` Takashi Iwai
2012-06-15 10:02 ` Pierre-Louis Bossart
2012-06-15 10:34 ` Takashi Iwai
-- strict thread matches above, loose matches on Subject: below --
2012-06-28 21:12 [PATCH 0/2] RFC: support for audio wall clock Pierre-Louis Bossart
2012-06-28 21:12 ` [PATCH 2/2] ALSA: hda: support for wallclock timestamps Pierre-Louis Bossart
2012-09-28 8:15 [PATCH 1/2] ALSA: core: add hooks for audio timestamps Pierre-Louis Bossart
2012-09-28 8:15 ` [PATCH 2/2] ALSA: hda: support for wallclock timestamps Pierre-Louis Bossart
2012-09-28 9:33 ` Clemens Ladisch
2012-09-29 20:12 ` Pierre-Louis Bossart
2012-09-30 10:12 ` Clemens Ladisch
2012-09-29 1:47 ` Raymond Yau
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