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

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
clock.

Signed-off-by: Matthias Reichl <hias@horus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files 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