Re: [PATCH v4] ASoC: sgtl5000: Fix driver probe after reset

[Troy Kisky <troy.kisky@boundarydevices.com>]

On 5/9/2013 3:55 PM, Fabio Estevam wrote:
> From: Fabio Estevam <fabio.estevam@freescale.com>
>
> After a 'reboot' command in Linux or after pressing the system's reset button
> the sgtl5000 driver fails to probe:
>
> sgtl5000 0-000a: Device with ID register ffff is not a sgtl5000
> sgtl5000 0-000a: ASoC: failed to probe CODEC -19
> imx-sgtl5000 sound.12: ASoC: failed to instantiate card -19
> imx-sgtl5000 sound.12: snd_soc_register_card failed (-19)
>
> sgtl5000 codec does not have a reset line, nor a reset command in software, so
> after a system reset the codec does not contain the default register values
> from sgtl5000_reg_defaults[] anymore, as these are only valid after a
> power-on-reset cycle.
>
> Fix this issue by explicitly reading all the reset register values from
> sgtl5000_reg_defaults[] and writing them back into sgtl5000 to ensure a sane
> state.
>
> Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
> ---
> Changes since v3:
> - Read sgtl5000_reg_defaults and write these values into sgtl5000
> Changes since v2:
> - Do not use reg_defaults_raw as it is not the correct purpose
> - Manually build sgtl5000_reg_default
> - Improve commitlog
> Changes since v1:
> - Remove sgtl5000_reg_defaults array
> - Do not use num_reg_defaults_raw
>   sound/soc/codecs/sgtl5000.c |   30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
>
> diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
> index 327b443..be23fce 100644
> --- a/sound/soc/codecs/sgtl5000.c
> +++ b/sound/soc/codecs/sgtl5000.c
> @@ -1474,6 +1474,31 @@ static const struct regmap_config sgtl5000_regmap = {
>   	.num_reg_defaults = ARRAY_SIZE(sgtl5000_reg_defaults),
>   };
>   
> +/*
> + * Write all the default values from sgtl5000_reg_defaults[] array into the
> + * sgtl5000 registers, to make sure we always start with the sane registers
> + * values as stated in the datasheet.
> + *
> + * Since sgtl5000 does not have a reset line, nor a reset command in software,
> + * we follow this approach to guarantee we always start from the default values
> + * and avoid problems like, not being able to probe after an audio playback
> + * followed by a system reset or a 'reboot' command in Linux
> + */
> +static int sgtl5000_fill_defaults(struct sgtl5000_priv *sgtl5000)
> +{
> +	int i, ret, val, index;
> +
> +	for (i = 0; i < ARRAY_SIZE(sgtl5000_reg_defaults); i++) {
> +		val = sgtl5000_reg_defaults[i].def;
> +		index = sgtl5000_reg_defaults[i].reg;
> +		ret = regmap_write(sgtl5000->regmap, index, val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
>   static int sgtl5000_i2c_probe(struct i2c_client *client,
>   			      const struct i2c_device_id *id)
>   {
> @@ -1494,6 +1519,11 @@ static int sgtl5000_i2c_probe(struct i2c_client *client,
>   
>   	i2c_set_clientdata(client, sgtl5000);
>   
> +	/* Ensure sgtl5000 will start with sane register values */
> +	ret = sgtl5000_fill_defaults(sgtl5000);
> +	if (ret)
> +		return ret;
> +
>   	ret = snd_soc_register_codec(&client->dev,
>   			&sgtl5000_driver, &sgtl5000_dai, 1);
>   	return ret;

It seems strange to write all the registers before even verifying that 
yes this is an SGTL5000.

Could you possibly write the 1 register that make SGTL5000_CHIP_ID read 
correctly,
and write the others afterwards?

Troy