ASoC: wm_adsp: Fix some subtle races on compressed stream

Firstly, we should be locking the pwr_lock when we initialise the
compressed buffer. Secondly, fixup a couple of places when we should be
pulling pointers only under the pwr_lock as they may be affected by
operations that take that lock.
Signed-off-by: NCharles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/codecs/wm_adsp.c

@@ -2240,9 +2240,13 @@ int wm_adsp2_event(struct snd_soc_dapm_widget *w,
 		if (ret != 0)
 			goto err;
 
+		mutex_lock(&dsp->pwr_lock);
+
 		if (wm_adsp_fw[dsp->fw].num_caps != 0)
 			ret = wm_adsp_buffer_init(dsp);
 
+		mutex_unlock(&dsp->pwr_lock);
+
 		break;
 
 	case SND_SOC_DAPM_PRE_PMD:
@@ -2814,12 +2818,15 @@ static int wm_adsp_buffer_update_avail(struct wm_adsp_compr_buf *buf)
 
 int wm_adsp_compr_handle_irq(struct wm_adsp *dsp)
 {
-	struct wm_adsp_compr_buf *buf = dsp->buffer;
-	struct wm_adsp_compr *compr = dsp->compr;
+	struct wm_adsp_compr_buf *buf;
+	struct wm_adsp_compr *compr;
 	int ret = 0;
 
 	mutex_lock(&dsp->pwr_lock);
 
+	buf = dsp->buffer;
+	compr = dsp->compr;
+
 	if (!buf) {
 		ret = -ENODEV;
 		goto out;
@@ -2879,14 +2886,16 @@ int wm_adsp_compr_pointer(struct snd_compr_stream *stream,
 			  struct snd_compr_tstamp *tstamp)
 {
 	struct wm_adsp_compr *compr = stream->runtime->private_data;
-	struct wm_adsp_compr_buf *buf = compr->buf;
 	struct wm_adsp *dsp = compr->dsp;
+	struct wm_adsp_compr_buf *buf;
 	int ret = 0;
 
 	adsp_dbg(dsp, "Pointer request\n");
 
 	mutex_lock(&dsp->pwr_lock);
 
+	buf = compr->buf;
+
 	if (!compr->buf) {
 		ret = -ENXIO;
 		goto out;