iio: adc: stm32: manage min sampling time on all internal channels

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>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20221012142205.13041-5-olivier.moysan@foss.st.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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;
 };
 
 /**
@@ -1910,14 +1910,15 @@ 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;
@@ -2568,6 +2569,9 @@ 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,
@@ -2581,8 +2585,12 @@ 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,
@@ -2597,9 +2605,12 @@ 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,
@@ -2610,6 +2621,7 @@ 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[] = {