[patch v2] iio: aspeed-adc: wait for initial sequence.

[Jonathan Cameron]

On Mon, 17 Jul 2017 12:00:35 +0300
Mykola Kostenok <c_mykolak at mellanox.com> wrote:

> This patch enables adc engine at initialization time and waits
> for the initial sequence completion before enabling adc channels.
> 
> Without this code adc channels are not functional and shows
> zeros for all connected channels.
> 
> Tested on mellanox msn platform.
> 
> v1 -> v2:
> Pointed by Rick Altherr:
>  - Wait init sequence code enabled by bool
> from OF match table.
> 
> Reviewed-by: Rick Altherr <raltherr at google.com>
> 
> Signed-off-by: Mykola Kostenok <c_mykolak at mellanox.com>

Applied to the fixes-togreg branch of iio.git and marked for
stable.

Thanks,

Jonathan
> ---
>  drivers/iio/adc/aspeed_adc.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
> index 2283ed2..cfa7ee1 100644
> --- a/drivers/iio/adc/aspeed_adc.c
> +++ b/drivers/iio/adc/aspeed_adc.c
> @@ -22,6 +22,7 @@
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/driver.h>
> +#include <linux/iopoll.h>
>  
>  #define ASPEED_RESOLUTION_BITS		10
>  #define ASPEED_CLOCKS_PER_SAMPLE	12
> @@ -38,11 +39,17 @@
>  
>  #define ASPEED_ENGINE_ENABLE		BIT(0)
>  
> +#define ASPEED_ADC_CTRL_INIT_RDY	BIT(8)
> +
> +#define ASPEED_ADC_INIT_POLLING_TIME	500
> +#define ASPEED_ADC_INIT_TIMEOUT		500000
> +
>  struct aspeed_adc_model_data {
>  	const char *model_name;
>  	unsigned int min_sampling_rate;	// Hz
>  	unsigned int max_sampling_rate;	// Hz
>  	unsigned int vref_voltage;	// mV
> +	bool wait_init_sequence;
>  };
>  
>  struct aspeed_adc_data {
> @@ -210,6 +217,24 @@ static int aspeed_adc_probe(struct platform_device *pdev)
>  		goto scaler_error;
>  	}
>  
> +	model_data = of_device_get_match_data(&pdev->dev);
> +
> +	if (model_data->wait_init_sequence) {
> +		/* Enable engine in normal mode. */
> +		writel(ASPEED_OPERATION_MODE_NORMAL | ASPEED_ENGINE_ENABLE,
> +		       data->base + ASPEED_REG_ENGINE_CONTROL);
> +
> +		/* Wait for initial sequence complete. */
> +		ret = readl_poll_timeout(data->base + ASPEED_REG_ENGINE_CONTROL,
> +					 adc_engine_control_reg_val,
> +					 adc_engine_control_reg_val &
> +					 ASPEED_ADC_CTRL_INIT_RDY,
> +					 ASPEED_ADC_INIT_POLLING_TIME,
> +					 ASPEED_ADC_INIT_TIMEOUT);
> +		if (ret)
> +			goto scaler_error;
> +	}
> +
>  	/* Start all channels in normal mode. */
>  	clk_prepare_enable(data->clk_scaler->clk);
>  	adc_engine_control_reg_val = GENMASK(31, 16) |
> @@ -269,6 +294,7 @@ static const struct aspeed_adc_model_data ast2500_model_data = {
>  	.vref_voltage = 1800, // mV
>  	.min_sampling_rate = 1,
>  	.max_sampling_rate = 1000000,
> +	.wait_init_sequence = true,
>  };
>  
>  static const struct of_device_id aspeed_adc_matches[] = {