From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: alsa-devel@alsa-project.org, sylvain.bertrand@gmail.com
Subject: Re: [alsa-devel] no period wakeup support
Date: Thu, 30 Jan 2020 16:06:43 +0900 [thread overview]
Message-ID: <20200130070642.GA7741@workstation> (raw)
In-Reply-To: <fffaf462-fd7a-6d09-e808-21d94f883365@linux.intel.com>
On Wed, Jan 29, 2020 at 05:43:19PM -0600, Pierre-Louis Bossart wrote:
> > Nowadays, is this reasonable to consider disabling the period wakeup as default
> > instead of expecting period wakeup by default?
>
> I'd say yes - it's been nearly 10 years since this capability was added, and
> it's quite common across HDaudio, Chrome, Android plaforms.
>
> But considering this as a default doesn't mean it's available in 100% of the
> cases, you still you need to check that
>
> a) the driver is capable of disabling the period wakeup
> b) the driver is capable of providing a precise position outside of period
> elapsed events (usually marked with the INFO_BATCH capability).
>
> alsa-lib gives you the means to query both cases.
>
> Note that you also have the case where you cannot disable interrupts but can
> still use timer-based solutions (e.g. for USB audio).
I suspect this advice.
In design of ALSA PCM core, runtime of PCM substream is configured for
the mode of no-period-wakeup just in a case that userspace application
requests it[1].
As long as developers take enough care of compatibility for existent
applications, it's better to support period wakeup for each IRQ as a
default, then support no-period-wakeup mode as an option.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/core/pcm_native.c#n715
Regards
Takashi Sakamoto
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next prev parent reply other threads:[~2020-01-30 7:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-29 23:23 [alsa-devel] no period wakeup support sylvain.bertrand
2020-01-29 23:43 ` Pierre-Louis Bossart
2020-01-30 1:20 ` sylvain.bertrand
2020-01-30 7:06 ` Takashi Sakamoto [this message]
2020-01-30 7:46 ` Jaroslav Kysela
2020-01-30 13:22 ` Pierre-Louis Bossart
2020-01-30 23:56 ` Takashi Sakamoto
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