On Wed, 2017-04-05 at 11:32 -0300, Fabio Estevam wrote:
> 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@xxxxxxx>
Hi
I could reproduce the channel swap issue on a Colibri iMX6 Dual
with a i.MX 6DualLite. Without the patch I see channel swap in
about 3% of playback starts. The patch fixes the issue with the
following change to the sgtl5000 device-tree node:
diff --git a/arch/arm/boot/dts/imx6qdl-colibri.dtsi b/arch/arm/boot/dts/imx6qdl-colibri.dtsi
index e6faa65..80ece03 100644
--- a/arch/arm/boot/dts/imx6qdl-colibri.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-colibri.dtsi
@@ -253,6 +253,7 @@
compatible = "fsl,sgtl5000";
reg = <0x0a>;
clocks = <&clks IMX6QDL_CLK_CKO>;
+ lrclk-strength = <0x3>;
VDDA-supply = <®_2p5v>;
VDDIO-supply = <®_3p3v>;
};
Tested-by: Max Krummenacher <max.krummenacher at toradex.com>
Max
> ---
> Documentation/devicetree/bindings/sound/sgtl5000.txt | 9 +++++++++
> sound/soc/codecs/sgtl5000.c | 19 ++++++++++++++++++-
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/sound/sgtl5000.txt b/Documentation/devicetree/bindings/sound/sgtl5000.txt
> index 5666da7..7a73a9d 100644
> --- 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 1589325..5a2702e 100644
> --- 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);
>
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