linux-kernel - Re: [PATCH v2 1/2] ALSA: dmaengine: Synchronize dma channel in prepare()

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Message-ID: <ZmgpUFy5-_5n_zyd@finisterre.sirena.org.uk>
Date: Tue, 11 Jun 2024 11:39:12 +0100
From: Mark Brown <broonie@...nel.org>
To: Lars-Peter Clausen <lars@...afoo.de>
Cc: Jai Luthra <j-luthra@...com>, Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>,
	Peter Ujfalusi <peter.ujfalusi@...il.com>,
	linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
	alsa-devel@...a-project.org, Devarsh Thakkar <devarsht@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Jayesh Choudhary <j-choudhary@...com>
Subject: Re: [PATCH v2 1/2] ALSA: dmaengine: Synchronize dma channel in
 prepare()

On Mon, Jun 10, 2024 at 05:45:52PM -0700, Lars-Peter Clausen wrote:
> On 6/10/24 03:56, Jai Luthra wrote:

> > Sometimes the stream may be stopped due to XRUN events, in which case
> > the userspace can call snd_pcm_drop() and snd_pcm_prepare() to stop and
> > start the stream again.

> > In these cases, we must wait for the DMA channel to synchronize before
> > marking the stream as prepared for playback, as the DMA channel gets
> > stopped by snd_pcm_drop() without any synchronization.

> We should really implement the sync_stop() PCM callback and let the ALSA
> core let care of the sync.

Good point, that's a better idea.

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