linux-kernel - [RFC PATCH v3 05/13] ASoC: soc-pcm: align BE 'atomicity' with that of the FE

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Message-Id: <20211013143050.244444-6-pierre-louis.bossart@linux.intel.com>
Date:   Wed, 13 Oct 2021 09:30:42 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        Sameer Pujar <spujar@...dia.com>,
        Gyeongtaek Lee <gt82.lee@...sung.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [RFC PATCH v3 05/13] ASoC: soc-pcm: align BE 'atomicity' with that of the FE

Since the flow for DPCM is based on taking a lock for the FE first, we
need to make sure during the connection between a BE and an FE that
they both use the same 'atomicity', otherwise we may sleep in atomic
context.

If the FE is nonatomic, this patch forces the BE to be nonatomic as
well. That should have no negative impact since the BE 'inherits' the
FE properties.

However, if the FE is atomic and the BE is not, then the configuration
is flagged as invalid.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 sound/soc/soc-pcm.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 52851827d53f..f22bbf95319d 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1151,13 +1151,33 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
 static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
+	struct snd_pcm_substream *fe_substream;
+	struct snd_pcm_substream *be_substream;
 	struct snd_soc_dpcm *dpcm;
 
 	/* only add new dpcms */
+	snd_soc_dpcm_fe_lock_irq(fe, stream);
 	for_each_dpcm_be(fe, stream, dpcm) {
-		if (dpcm->be == be && dpcm->fe == fe)
+		if (dpcm->be == be && dpcm->fe == fe) {
+			snd_soc_dpcm_fe_unlock_irq(fe, stream);
 			return 0;
+		}
+	}
+	fe_substream = snd_soc_dpcm_get_substream(fe, stream);
+	be_substream = snd_soc_dpcm_get_substream(be, stream);
+
+	if (!fe_substream->pcm->nonatomic && be_substream->pcm->nonatomic) {
+		dev_err(be->dev, "%s: FE is atomic but BE is nonatomic, invalid configuration\n",
+			__func__);
+		snd_soc_dpcm_fe_unlock_irq(fe, stream);
+		return -EINVAL;
 	}
+	if (fe_substream->pcm->nonatomic && !be_substream->pcm->nonatomic) {
+		dev_warn(be->dev, "%s: FE is nonatomic but BE is not, forcing BE as nonatomic\n",
+			 __func__);
+		be_substream->pcm->nonatomic = 1;
+	}
+	snd_soc_dpcm_fe_unlock_irq(fe, stream);
 
 	dpcm = kzalloc(sizeof(struct snd_soc_dpcm), GFP_KERNEL);
 	if (!dpcm)
-- 
2.25.1