Applied "ASoC: bcm2835: fix hw_params error when device is in prepared state" to the asoc tree

Mark Brown broonie at
Thu Jan 18 03:22:47 PST 2018

The patch

   ASoC: bcm2835: fix hw_params error when device is in prepared state

has been applied to the asoc tree at 

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>From 8d5737a5f53902a916ee1e1cb248c9b8b883b2ea Mon Sep 17 00:00:00 2001
From: Matthias Reichl <hias at>
Date: Wed, 17 Jan 2018 13:50:50 +0100
Subject: [PATCH] ASoC: bcm2835: fix hw_params error when device is in prepared

If bcm2835 is configured as bitclock master calling hw_params()
after prepare() fails with EBUSY. This also makes it impossible to
use bcm2835 in full duplex mode.

The error is caused by the split clock setup: clk_set_rate
is called in hw_params, clk_prepare_enable in prepare. As hw_params
doesn't check if the clock was already enabled clk_set_rate
fails with EBUSY.

Fix this by moving clock startup from prepare to hw_params and
let hw_params properly deal with an already set up or enabled

Signed-off-by: Matthias Reichl <hias at>
Signed-off-by: Mark Brown <broonie at>
 sound/soc/bcm/bcm2835-i2s.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/sound/soc/bcm/bcm2835-i2s.c b/sound/soc/bcm/bcm2835-i2s.c
index 2e449d7173fc..d5f73a8ab893 100644
--- a/sound/soc/bcm/bcm2835-i2s.c
+++ b/sound/soc/bcm/bcm2835-i2s.c
@@ -130,6 +130,7 @@ struct bcm2835_i2s_dev {
 	struct regmap				*i2s_regmap;
 	struct clk				*clk;
 	bool					clk_prepared;
+	int					clk_rate;
 static void bcm2835_i2s_start_clock(struct bcm2835_i2s_dev *dev)
@@ -419,10 +420,19 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
 	/* Clock should only be set up here if CPU is clock master */
-	if (bit_clock_master) {
-		ret = clk_set_rate(dev->clk, bclk_rate);
-		if (ret)
-			return ret;
+	if (bit_clock_master &&
+	    (!dev->clk_prepared || dev->clk_rate != bclk_rate)) {
+		if (dev->clk_prepared)
+			bcm2835_i2s_stop_clock(dev);
+		if (dev->clk_rate != bclk_rate) {
+			ret = clk_set_rate(dev->clk, bclk_rate);
+			if (ret)
+				return ret;
+			dev->clk_rate = bclk_rate;
+		}
+		bcm2835_i2s_start_clock(dev);
 	/* Setup the frame format */
@@ -618,8 +628,6 @@ static int bcm2835_i2s_prepare(struct snd_pcm_substream *substream,
 	struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
 	uint32_t cs_reg;
-	bcm2835_i2s_start_clock(dev);
 	 * Clear both FIFOs if the one that should be started
 	 * is not empty at the moment. This should only happen

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