CHROMIUM: ASoC: samsung: initialize pll and audio bus clock rate

In the daisy_max98095 driver we rely on EPLL being set to a rate below
the limit of the AudioSS block (192Mhz on 5250 and 200Mhz on 5420) and
the audio bus divider being set to 1.  On Pit, neither of these are
initialized correctly, so explicitly set fout_epll to a reasonable
rate and then set sclk_audio0 to that rate to ensure that the audio
bus divider is 1.

BUG=chrome-os-partner:18720
TEST=Audio still works on snow; peach-pit no longer hangs when
daisy_max98095 driver is probed.

Change-Id: I5dd811078d7964979e0c58d9937163e1d3a58850
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/57708
Reviewed-by: Simon Glass <sjg@chromium.org>

Author: abrestic

sound/soc/samsung/daisy_max98095.c

@@ -42,6 +42,13 @@
 
 #define DRV_NAME "daisy-snd-max98095"
 
+/*
+ * The initial rate that EPLL will be set to.  This is the smallest multiple (4)
+ * of the desired master clock frequency 256 * FS for FS = 44.1khz that can
+ * be generated on both the 5250 and 5420 SoCs.
+ */
+#define DEFAULT_EPLL_RATE (256 * 44100 * 4)
+
 /* Audio clock settings are belonged to board specific part. Every
  * board can set audio source clock setting which is matched with H/W
  * like this function-'set_audio_clock_heirachy'.
@@ -96,6 +103,20 @@ static int set_audio_clock_heirachy(struct platform_device *pdev)
 		goto out5;
 	}
 
+	/*
+	 * fout_epll may have been initialized to operate at a frequency higher
+	 * than the audio block's maximum (192Mhz on 5250, 200Mhz on 5420),
+	 * so lower it to a reasonable rate here.  If we attempt to set
+	 * fout_epll as the parent of mout_audss when fout_epll is operating
+	 * at a frequency higher than the audio block's maximum, the system
+	 * may hang.
+	 */
+	ret = clk_set_rate(fout_epll, DEFAULT_EPLL_RATE);
+	if (ret < 0) {
+		printk(KERN_WARNING "Failed to set epll rate.\n");
+		goto out6;
+	}
+
 	/* Set audio clock hierarchy for S/PDIF */
 	if (clk_set_parent(sclk_epll, fout_epll))
 		printk(KERN_WARNING "Failed to set parent of epll.\n");
@@ -106,6 +127,13 @@ static int set_audio_clock_heirachy(struct platform_device *pdev)
 	if (clk_set_parent(mout_i2s, sclk_audio0))
 		printk(KERN_WARNING "Failed to set parent of mout i2s.\n");
 
+	/* Ensure that the divider between mout_audio0 and sclk_audio0 is 1. */
+	ret = clk_set_rate(sclk_audio0, clk_get_rate(mout_audio0));
+	if (ret < 0)
+		printk(KERN_WARNING "Failed to set audio bus rate (%d).\n",
+			ret);
+
+out6:
 	clk_put(mout_i2s);
 out5:
 	clk_put(mout_audss);