ASoC: sgtl5000: Allow LRCLK pad drive strength to be changed

Introduce the "lrclk-strength" property to allow LRCLK pad drive strength
to be changed via device tree.

When running a stress playback loop test on a mx6dl wandboard channel
swap can be noticed on about 10% of the times.

While debugging this issue I noticed that when probing the SGTL5000
LRCLK pin with the scope the swap did not happen. After removing
the probe the swap started to happen again.

After changing the LRCLK pad drive strength to the maximum value the
issue is gone.

Same fix works on a mx6dl Colibri board as well.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/devicetree/bindings/sound/sgtl5000.txt b/Documentation/devicetree/bindings/sound/sgtl5000.txt
index 5666da7b86059f39c411a6acebf5b8dc758342ac..7a73a9d62015ecc600af3c3f1c69f001b180b410 100644 (file)
--- a/Documentation/devicetree/bindings/sound/sgtl5000.txt
+++ b/Documentation/devicetree/bindings/sound/sgtl5000.txt
@@ -26,6 +26,15 @@ Optional properties:
        If this node is not mentioned or the value is unknown, then
        the value is set to 1.25V.
 
+- lrclk-strength: the LRCLK pad strength. Possible values are:
+0, 1, 2 and 3 as per the table below:
+
+VDDIO          1.8V            2.5V            3.3V
+0 =            Disable
+1 =            1.66 mA         2.87 mA         4.02  mA
+2 =            3.33 mA         5.74 mA         8.03  mA
+3 =            4.99 mA         8.61 mA         12.05 mA
+
 Example:
 
 codec: sgtl5000@0a {

diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
index 1589325855bc10ca41c1180de3e06b745d32ee19..5a2702edeb7709b765d744c6db8f11992c36a1ff 100644 (file)
--- a/sound/soc/codecs/sgtl5000.c
+++ b/sound/soc/codecs/sgtl5000.c
@@ -99,6 +99,13 @@ enum sgtl5000_micbias_resistor {
        SGTL5000_MICBIAS_8K = 8,
 };
 
+enum  {
+       I2S_LRCLK_STRENGTH_DISABLE,
+       I2S_LRCLK_STRENGTH_LOW,
+       I2S_LRCLK_STRENGTH_MEDIUM,
+       I2S_LRCLK_STRENGTH_HIGH,
+};
+
 /* sgtl5000 private structure in codec */
 struct sgtl5000_priv {
        int sysclk;     /* sysclk rate */
@@ -111,6 +118,7 @@ struct sgtl5000_priv {
        int revision;
        u8 micbias_resistor;
        u8 micbias_voltage;
+       u8 lrclk_strength;
 };
 
 /*
@@ -1089,6 +1097,7 @@ static int sgtl5000_enable_regulators(struct i2c_client *client)
 static int sgtl5000_probe(struct snd_soc_codec *codec)
 {
        int ret;
+       u16 reg;
        struct sgtl5000_priv *sgtl5000 = snd_soc_codec_get_drvdata(codec);
 
        /* power up sgtl5000 */
@@ -1118,7 +1127,8 @@ static int sgtl5000_probe(struct snd_soc_codec *codec)
                        SGTL5000_DAC_MUTE_RIGHT |
                        SGTL5000_DAC_MUTE_LEFT);
 
-       snd_soc_write(codec, SGTL5000_CHIP_PAD_STRENGTH, 0x015f);
+       reg = ((sgtl5000->lrclk_strength) << SGTL5000_PAD_I2S_LRCLK_SHIFT | 0x5f);
+       snd_soc_write(codec, SGTL5000_CHIP_PAD_STRENGTH, reg);
 
        snd_soc_write(codec, SGTL5000_CHIP_ANA_CTRL,
                        SGTL5000_HP_ZCD_EN |
@@ -1347,6 +1357,13 @@ static int sgtl5000_i2c_probe(struct i2c_client *client,
                }
        }
 
+       sgtl5000->lrclk_strength = I2S_LRCLK_STRENGTH_LOW;
+       if (!of_property_read_u32(np, "lrclk-strength", &value)) {
+               if (value > I2S_LRCLK_STRENGTH_HIGH)
+                       value = I2S_LRCLK_STRENGTH_LOW;
+               sgtl5000->lrclk_strength = value;
+       }
+
        /* Ensure sgtl5000 will start with sane register values */
        sgtl5000_fill_defaults(client);