From: Pavel Machek <pavel@ucw.cz>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: alsa-devel@alsa-project.org,
"Ivaylo Dimitrov" <ivo.g.dimitrov.75@gmail.com>,
"Aaro Koskinen" <aaro.koskinen@iki.fi>,
"Tony Lindgren" <tony@atomide.com>,
"Liam Girdwood" <lgirdwood@gmail.com>,
"Sebastian Reichel" <sre@kernel.org>,
"Kristo, Tero" <t-kristo@ti.com>,
"Mark Brown" <broonie@kernel.org>,
"Jarkko Nikula" <jarkko.nikula@linux.intel.com>,
"Pali Rohár" <pali.rohar@gmail.com>,
linux-omap@vger.kernel.org
Subject: Re: [PATCH] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches
Date: Fri, 2 Sep 2016 17:54:37 +0200 [thread overview]
Message-ID: <20160902155437.GA4152@amd> (raw)
In-Reply-To: <b3a254b2-948f-f04d-3289-fb8fb9f9ab23@ti.com>
Hi!
> >> When the FIFO is set to 128, it means that after the initial FIFO fill we will
> >> have DMA request coming from McBSP to sDMA with a rate of:
> >>
> >> (1000/sampling_rate) * (FIFO-threshold / channels) = DMA_req_distance_in_ms
> >>
> >> So in case of 44.1KHz, stereo with 128 FIFO threshold DMA request will come at
> >> every 1.45ms. If I'm not mistaken. The whole FIFO (1280) holds 14.51ms of
> >> audio in this case.
> >>
> >> I don't see this correlate with the 30ms at all.
> >
> > It seems we easily have a situation where DMA is done buffering to McBSP,
> > and PMIC is playing audio, and we hit idle. At that point there are no immediate
> > timers pending and cpuidle determines we can try to hit a deeper idle mode. As
> > there are no hardware blockers with DMA off and McBSP not blocking, the hardware
> > hits off mode. This cuts power to McBSP.
> >
> > Ideally we'd configure McBSP activity to block deeper idle states in the
> > hardware but I don't think we have such a configuration available.
>
> I wonder why we have not seen this before? I can not recall anything like this
> with n900 (Jarkko might know that better) neither with n9/n950. On the n9/n950
> I have even put the OMAP3 to OFF during audio playback with the
I was seeing something like that with 4.x kernel on Nokia N900.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2016-09-02 15:54 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-29 18:27 [PATCH] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches Tony Lindgren
[not found] ` <201608300739.JrTVlIyd%fengguang.wu@intel.com>
2016-08-30 18:38 ` Tony Lindgren
2016-08-31 17:24 ` Mark Brown
2016-08-31 17:42 ` Tony Lindgren
2016-08-31 11:37 ` Peter Ujfalusi
2016-08-31 14:13 ` Tony Lindgren
2016-08-31 16:59 ` Tony Lindgren
2016-08-31 18:33 ` Peter Ujfalusi
2016-08-31 19:41 ` Tony Lindgren
2016-09-01 6:57 ` Peter Ujfalusi
2016-09-01 14:50 ` Tony Lindgren
2016-09-02 7:30 ` Peter Ujfalusi
2016-09-02 14:56 ` Tony Lindgren
2016-09-02 19:38 ` Peter Ujfalusi
2016-09-02 20:40 ` Tony Lindgren
2016-09-05 7:53 ` Peter Ujfalusi
2016-09-06 20:16 ` Tony Lindgren
2016-09-07 14:31 ` Peter Ujfalusi
2016-09-08 3:53 ` Tony Lindgren
2016-09-08 10:41 ` Peter Ujfalusi
2016-09-08 10:49 ` Peter Ujfalusi
2016-09-08 14:48 ` Tony Lindgren
2016-09-09 6:51 ` Peter Ujfalusi
2016-09-09 23:45 ` Tony Lindgren
2016-09-13 11:45 ` Peter Ujfalusi
2016-09-13 13:45 ` Tony Lindgren
2016-09-02 15:54 ` Pavel Machek [this message]
2016-09-02 19:45 ` Peter Ujfalusi
2016-09-02 20:09 ` Tony Lindgren
2016-09-03 16:08 ` Sebastian Reichel
2016-09-06 20:08 ` Tony Lindgren
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