[PATCH linux dev-4.10] iio: aspeed-adc: wait for initial sequence.

[Rick Altherr]

Huh.  We've been getting valid readings without this on our AST2500
systems.  Regardless, it is correct for AST2500.  On AST2400 though, there
is no INIT_RDY bit.

On Thu, Jul 13, 2017 at 7:28 AM, 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.
>
> Signed-off-by: Mykola Kostenok <c_mykolak at mellanox.com>
> ---
>  drivers/iio/adc/aspeed_adc.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
> index 2283ed2..e4ad6ef 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
> @@ -38,6 +39,11 @@
>
>  #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
> @@ -210,6 +216,20 @@ static int aspeed_adc_probe(struct platform_device
> *pdev)
>                 goto scaler_error;
>         }
>
> +       /* 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) |
> --
> 2.8.4
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ozlabs.org/pipermail/openbmc/attachments/20170713/6876e7b2/attachment.html>