linux-kernel - Re: [PATCH review for 4.9 39/50] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches

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Date:   Mon, 9 Oct 2017 09:36:56 +0100
From:   Mark Brown <broonie@...nel.org>
To:     "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Matt Ranostay <matt@...ostay.consulting>,
        Liam Breck <kernel@...workimprov.net>
Subject: Re: [PATCH review for 4.9 39/50] ASoC: omap-mcbsp: Add PM QoS
 support for McBSP to prevent glitches

On Sat, Oct 07, 2017 at 10:36:55PM +0000, Levin, Alexander (Sasha Levin) wrote:
> From: Matt Ranostay <matt@...ostay.consulting>
> 
> [ Upstream commit 9834ffd1ecc3a401d0ce64c2d4235a726da6d4f9 ]
> 
> We can get audio errors if hitting deeper idle states on omaps:
> 
> [alsa.c:230] error: Fatal problem with alsa output, error -5.
> [audio.c:614] error: Error in writing audio (Input/output error?)!
> 
> This seems to happen with off mode idle enabled as power for the
> whole SoC may get cut off between filling the McBSP fifo using DMA.
> While active DMA blocks deeper idle states in hardware, McBSP
> activity does not seem to do so.

This seems rather invasive and fancy for stable material - people might
want it in production but they may also not have enough power management
enabled to be seeing the problems it fixes.

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