ASoC: mxs-saif: fix clock prepare and enable unbalance issue

Currently we directly call a clock_enable in trigger function without
a clk_prepare as pair first.
This will cause system hang immediately when run capture because
the clock was not prepared(playback does not hang because the clock was
prepared already by get_mclk before), a warning message in clock framework
may cause a deadlock to reclaim clock lock (see: pl011_console_write).

Here we prepare clock first in hw_param, then enable it in trigger
function to guarantee the balance.
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/mxs/mxs-saif.c

@@ -394,9 +394,14 @@ static int mxs_saif_hw_params(struct snd_pcm_substream *substream,
 			     struct snd_soc_dai *cpu_dai)
 {
 	struct mxs_saif *saif = snd_soc_dai_get_drvdata(cpu_dai);
+	struct mxs_saif *master_saif;
 	u32 scr, stat;
 	int ret;
 
+	master_saif = mxs_saif_get_master(saif);
+	if (!master_saif)
+		return -EINVAL;
+
 	/* mclk should already be set */
 	if (!saif->mclk && saif->mclk_in_use) {
 		dev_err(cpu_dai->dev, "set mclk first\n");
@@ -420,6 +425,11 @@ static int mxs_saif_hw_params(struct snd_pcm_substream *substream,
 		return ret;
 	}
 
+	/* prepare clk in hw_param, enable in trigger */
+	clk_prepare(saif->clk);
+	if (saif != master_saif)
+		clk_prepare(master_saif->clk);
+
 	scr = __raw_readl(saif->base + SAIF_CTRL);
 
 	scr &= ~BM_SAIF_CTRL_WORD_LENGTH;