diff options
| -rw-r--r-- | Documentation/devicetree/bindings/arm/atmel-adc.txt | 1 | ||||
| -rw-r--r-- | drivers/iio/adc/at91_adc.c | 15 |
2 files changed, 15 insertions, 1 deletions
diff --git a/Documentation/devicetree/bindings/arm/atmel-adc.txt b/Documentation/devicetree/bindings/arm/atmel-adc.txt index 3a05492acda..16769d9cedd 100644 --- a/Documentation/devicetree/bindings/arm/atmel-adc.txt +++ b/Documentation/devicetree/bindings/arm/atmel-adc.txt @@ -26,6 +26,7 @@ Optional properties: atmel,adc-res-names property. If not specified, the highest resolution will be used. - atmel,adc-sleep-mode: Boolean to enable sleep mode when no conversion + - atmel,adc-sample-hold-time: Sample and Hold Time in microseconds Optional trigger Nodes: - Required properties: diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c index 7295bc5280b..e5b88d5d3b5 100644 --- a/drivers/iio/adc/at91_adc.c +++ b/drivers/iio/adc/at91_adc.c @@ -52,6 +52,7 @@ struct at91_adc_state { void __iomem *reg_base; struct at91_adc_reg_desc *registers; u8 startup_time; + u8 sample_hold_time; bool sleep_mode; struct iio_trigger **trig; struct at91_adc_trigger *trigger_list; @@ -465,6 +466,9 @@ static int at91_adc_probe_dt(struct at91_adc_state *st, } st->startup_time = prop; + prop = 0; + of_property_read_u32(node, "atmel,adc-sample-hold-time", &prop); + st->sample_hold_time = prop; if (of_property_read_u32(node, "atmel,adc-vref", &prop)) { dev_err(&idev->dev, "Missing adc-vref property in the DT.\n"); @@ -578,7 +582,7 @@ static const struct iio_info at91_adc_info = { static int at91_adc_probe(struct platform_device *pdev) { - unsigned int prsc, mstrclk, ticks, adc_clk; + unsigned int prsc, mstrclk, ticks, adc_clk, shtim; int ret; struct iio_dev *idev; struct at91_adc_state *st; @@ -691,12 +695,21 @@ static int at91_adc_probe(struct platform_device *pdev) */ ticks = round_up((st->startup_time * adc_clk / 1000000) - 1, 8) / 8; + /* + * a minimal Sample and Hold Time is necessary for the ADC to guarantee + * the best converted final value between two channels selection + * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock + */ + shtim = round_up((st->sample_hold_time * adc_clk / + 1000000) - 1, 1); + reg = AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL; reg |= AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP; if (st->low_res) reg |= AT91_ADC_LOWRES; if (st->sleep_mode) reg |= AT91_ADC_SLEEP; + reg |= AT91_ADC_SHTIM_(shtim) & AT91_ADC_SHTIM; at91_adc_writel(st, AT91_ADC_MR, reg); /* Setup the ADC channels available on the board */ |