ASoC: Disable register synchronisation for low frequency WM8996 SYSCLK

commit fed22007 upstream.

With a low frequency SYSCLK and a fast I2C clock register synchronisation
may occasionally take too long to take effect, causing I/O issues. Disable
synchronisation in order to avoid any issues.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sound/soc/codecs/wm8996.c

@@ -1932,6 +1932,7 @@ static int wm8996_set_sysclk(struct snd_soc_dai *dai,
 	struct wm8996_priv *wm8996 = snd_soc_codec_get_drvdata(codec);
 	int lfclk = 0;
 	int ratediv = 0;
+	int sync = WM8996_REG_SYNC;
 	int src;
 	int old;
 
@@ -1976,6 +1977,7 @@ static int wm8996_set_sysclk(struct snd_soc_dai *dai,
 	case 32000:
 	case 32768:
 		lfclk = WM8996_LFCLK_ENA;
+		sync = 0;
 		break;
 	default:
 		dev_warn(codec->dev, "Unsupported clock rate %dHz\n",
@@ -1989,6 +1991,8 @@ static int wm8996_set_sysclk(struct snd_soc_dai *dai,
 			    WM8996_SYSCLK_SRC_MASK | WM8996_SYSCLK_DIV_MASK,
 			    src << WM8996_SYSCLK_SRC_SHIFT | ratediv);
 	snd_soc_update_bits(codec, WM8996_CLOCKING_1, WM8996_LFCLK_ENA, lfclk);
+	snd_soc_update_bits(codec, WM8996_CONTROL_INTERFACE_1,
+			    WM8996_REG_SYNC, sync);
 	snd_soc_update_bits(codec, WM8996_AIF_CLOCKING_1,
 			    WM8996_SYSCLK_ENA, old);
 

sound/soc/codecs/wm8996.h

@@ -1567,6 +1567,10 @@ int wm8996_detect(struct snd_soc_codec *codec, struct snd_soc_jack *jack,
 /*
  * R257 (0x101) - Control Interface (1)
  */
+#define WM8996_REG_SYNC                         0x8000  /* REG_SYNC */
+#define WM8996_REG_SYNC_MASK                    0x8000  /* REG_SYNC */
+#define WM8996_REG_SYNC_SHIFT                       15  /* REG_SYNC */
+#define WM8996_REG_SYNC_WIDTH                        1  /* REG_SYNC */
 #define WM8996_AUTO_INC                         0x0004  /* AUTO_INC */
 #define WM8996_AUTO_INC_MASK                    0x0004  /* AUTO_INC */
 #define WM8996_AUTO_INC_SHIFT                        2  /* AUTO_INC */