Re: [RFC PATCH v1 2/2] iio: adc: meson: add support for the GXLX SoC

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 31 Dec 2024 20:42:07 +0100
Martin Blumenstingl <martin.blumenstingl@googlemail.com> wrote:

> The SARADC IP on the GXLX SoC itself is identical to the one found on
> GXL SoCs. However, GXLX SoCs require poking the first three bits in the
> MESON_SAR_ADC_REG12 register to get the three MPLL clocks (used as clock
> generators for the audio frequencies) to work.
> 
> The reason why there are MPLL clock bits in the ADC register space is
> entirely unknown and it seems that nobody is able to comment on this.
> So clearly mark this as a workaround and add a warning so users are
> notified that this workaround can change (once we know what these bits
> actually do).

So IIUC this is to make some non ADC component work.
How are you handling dependencies?  The ADC driver might not be loaded or
is there some reason it definitely is at the point where the audio driver
loads?

Jonathan

> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> ---
>  drivers/iio/adc/meson_saradc.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> index 997def4a4d2f..df15a2566ec7 100644
> --- a/drivers/iio/adc/meson_saradc.c
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -160,6 +160,11 @@
>  	#define MESON_SAR_ADC_REG11_EOC				BIT(1)
>  	#define MESON_SAR_ADC_REG11_VREF_SEL			BIT(0)
>  
> +#define MESON_SAR_ADC_REG12					0x30
> +	#define MESON_SAR_ADC_REG12_MPLL0_UNKNOWN		BIT(0)
> +	#define MESON_SAR_ADC_REG12_MPLL1_UNKNOWN		BIT(1)
> +	#define MESON_SAR_ADC_REG12_MPLL2_UNKNOWN		BIT(2)
> +
>  #define MESON_SAR_ADC_REG13					0x34
>  	#define MESON_SAR_ADC_REG13_12BIT_CALIBRATION_MASK	GENMASK(13, 8)
>  
> @@ -326,6 +331,7 @@ struct meson_sar_adc_param {
>  	u8					cmv_select;
>  	u8					adc_eoc;
>  	enum meson_sar_adc_vref_sel		vref_voltage;
> +	bool					enable_mpll_clock_workaround;
>  };
>  
>  struct meson_sar_adc_data {
> @@ -995,6 +1001,15 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
>  				    priv->param->cmv_select);
>  		regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG11,
>  				   MESON_SAR_ADC_REG11_CMV_SEL, regval);
> +
> +		if (priv->param->enable_mpll_clock_workaround) {
> +			dev_warn(dev,
> +				 "Enabling unknown bits to make the MPLL clocks work. This may change so always update dtbs and kernel together\n");
> +			regmap_write(priv->regmap, MESON_SAR_ADC_REG12,
> +				     MESON_SAR_ADC_REG12_MPLL0_UNKNOWN |
> +				     MESON_SAR_ADC_REG12_MPLL1_UNKNOWN |
> +				     MESON_SAR_ADC_REG12_MPLL2_UNKNOWN);
> +		}
>  	}
>  
>  	ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
> @@ -1219,6 +1234,17 @@ static const struct meson_sar_adc_param meson_sar_adc_gxl_param = {
>  	.cmv_select = 1,
>  };
>  
> +static const struct meson_sar_adc_param meson_sar_adc_gxlx_param = {
> +	.has_bl30_integration = true,
> +	.clock_rate = 1200000,
> +	.regmap_config = &meson_sar_adc_regmap_config_gxbb,
> +	.resolution = 12,
> +	.disable_ring_counter = 1,
> +	.vref_voltage = VREF_VOLTAGE_1V8,
> +	.cmv_select = true,
> +	.enable_mpll_clock_workaround = true,
> +};
> +
>  static const struct meson_sar_adc_param meson_sar_adc_axg_param = {
>  	.has_bl30_integration = true,
>  	.clock_rate = 1200000,
> @@ -1267,6 +1293,11 @@ static const struct meson_sar_adc_data meson_sar_adc_gxl_data = {
>  	.name = "meson-gxl-saradc",
>  };
>  
> +static const struct meson_sar_adc_data meson_sar_adc_gxlx_data = {
> +	.param = &meson_sar_adc_gxlx_param,
> +	.name = "meson-gxlx-saradc",
> +};
> +
>  static const struct meson_sar_adc_data meson_sar_adc_gxm_data = {
>  	.param = &meson_sar_adc_gxl_param,
>  	.name = "meson-gxm-saradc",
> @@ -1298,6 +1329,9 @@ static const struct of_device_id meson_sar_adc_of_match[] = {
>  	}, {
>  		.compatible = "amlogic,meson-gxl-saradc",
>  		.data = &meson_sar_adc_gxl_data,
> +	}, {
> +		.compatible = "amlogic,meson-gxlx-saradc",
> +		.data = &meson_sar_adc_gxlx_data,
>  	}, {
>  		.compatible = "amlogic,meson-gxm-saradc",
>  		.data = &meson_sar_adc_gxm_data,