[PATCH 4/8] iio: adc: stm32: manage min sampling time on all internal channels

Olivier Moysan
2022-09-28T16:43:52Z

Force minimum sampling time for all internal channels according
to datasheet requirement. This value can be increased through
DT st,min-sample-time-ns property.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
drivers/iio/adc/stm32-adc.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 362db64bbd69..10eb0acc9327 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -215,7 +215,7 @@ struct stm32_adc;
* @unprepare: optional unprepare routine (disable, power-down)
* @irq_clear: routine to clear irqs
* @smp_cycles: programmable sampling time (ADC clock cycles)
- * @ts_vrefint_ns: vrefint minimum sampling time in ns
+ * @ts_int_ch: pointer to array of internal channels minimum sampling time in ns
*/
struct stm32_adc_cfg {
const struct stm32_adc_regspec *regs;
@@ -232,7 +232,7 @@ struct stm32_adc_cfg {
void (*unprepare)(struct iio_dev *);
void (*irq_clear)(struct iio_dev *indio_dev, u32 msk);
const unsigned int *smp_cycles;
- const unsigned int ts_vrefint_ns;
+ const unsigned int *ts_int_ch;
};

/**
@@ -1909,14 +1909,15 @@ static void stm32_adc_smpr_init(struct stm32_adc *adc, int channel, u32 smp_ns)
{
const struct stm32_adc_regs *smpr = &adc->cfg->regs->smp_bits[channel];
u32 period_ns, shift = smpr->shift, mask = smpr->mask;
- unsigned int smp, r = smpr->reg;
+ unsigned int i, smp, r = smpr->reg;

/*
- * For vrefint channel, ensure that the sampling time cannot
+ * For internal channels, ensure that the sampling time cannot
* be lower than the one specified in the datasheet
*/
- if (channel == adc->int_ch[STM32_ADC_INT_CH_VREFINT])
- smp_ns = max(smp_ns, adc->cfg->ts_vrefint_ns);
+ for (i = 0; i < STM32_ADC_INT_CH_NB; i++)
+ if (channel == adc->int_ch[i] && adc->int_ch[i] != STM32_ADC_INT_CH_NONE)
+ smp_ns = max(smp_ns, adc->cfg->ts_int_ch[i]);

/* Determine sampling time (ADC clock cycles) */
period_ns = NSEC_PER_SEC / adc->common->rate;
@@ -2567,6 +2568,9 @@ static const struct stm32_adc_cfg stm32f4_adc_cfg = {
.irq_clear = stm32f4_adc_irq_clear,
};

+const unsigned int stm32_adc_min_ts_h7[] = { 0, 0, 0, 4300, 9000 };
+static_assert(ARRAY_SIZE(stm32_adc_min_ts_h7) == STM32_ADC_INT_CH_NB);
+
static const struct stm32_adc_cfg stm32h7_adc_cfg = {
.regs = &stm32h7_adc_regspec,
.adc_info = &stm32h7_adc_info,
@@ -2580,8 +2584,12 @@ static const struct stm32_adc_cfg stm32h7_adc_cfg = {
.unprepare = stm32h7_adc_unprepare,
.smp_cycles = stm32h7_adc_smp_cycles,
.irq_clear = stm32h7_adc_irq_clear,
+ .ts_int_ch = stm32_adc_min_ts_h7,
};

+const unsigned int stm32_adc_min_ts_mp1[] = { 100, 100, 100, 4300, 9800 };
+static_assert(ARRAY_SIZE(stm32_adc_min_ts_mp1) == STM32_ADC_INT_CH_NB);
+
static const struct stm32_adc_cfg stm32mp1_adc_cfg = {
.regs = &stm32mp1_adc_regspec,
.adc_info = &stm32h7_adc_info,
@@ -2596,9 +2604,12 @@ static const struct stm32_adc_cfg stm32mp1_adc_cfg = {
.unprepare = stm32h7_adc_unprepare,
.smp_cycles = stm32h7_adc_smp_cycles,
.irq_clear = stm32h7_adc_irq_clear,
- .ts_vrefint_ns = 4300,
+ .ts_int_ch = stm32_adc_min_ts_mp1,
};

+const unsigned int stm32_adc_min_ts_mp13[] = { 100, 0, 0, 4300, 9800 };
+static_assert(ARRAY_SIZE(stm32_adc_min_ts_mp13) == STM32_ADC_INT_CH_NB);
+
static const struct stm32_adc_cfg stm32mp13_adc_cfg = {
.regs = &stm32mp13_adc_regspec,
.adc_info = &stm32mp13_adc_info,
@@ -2609,6 +2620,7 @@ static const struct stm32_adc_cfg stm32mp13_adc_cfg = {
.unprepare = stm32h7_adc_unprepare,
.smp_cycles = stm32mp13_adc_smp_cycles,
.irq_clear = stm32h7_adc_irq_clear,
+ .ts_int_ch = stm32_adc_min_ts_mp13,
};

static const struct of_device_id stm32_adc_of_match[] = {