[PATCH v5 05/10] counter: stm32-timer-cnt: add counter prescaler extension

[Fabrice Gasnier]

There's a prescaler in between the selected input signal used for
counting (CK_PSC), and the counter input (CK_CNT).
So add the "prescaler" extension to the counter.

Reviewed-by: William Breathitt Gray <william.gray@xxxxxxxxxx>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>
---
Changes in v4:
- Add William's Reviewed-by tag
Changes in v3:
- New patch split from "counter: stm32-timer-cnt: introduce clock signal"
---
 drivers/counter/stm32-timer-cnt.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index 65b447b42e75..b969d550e90a 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -220,11 +220,40 @@ static int stm32_count_enable_write(struct counter_device *counter,
 	return 0;
 }
 
+static int stm32_count_prescaler_read(struct counter_device *counter,
+				      struct counter_count *count, u64 *prescaler)
+{
+	struct stm32_timer_cnt *const priv = counter_priv(counter);
+	u32 psc;
+
+	regmap_read(priv->regmap, TIM_PSC, &psc);
+
+	*prescaler = psc + 1;
+
+	return 0;
+}
+
+static int stm32_count_prescaler_write(struct counter_device *counter,
+				       struct counter_count *count, u64 prescaler)
+{
+	struct stm32_timer_cnt *const priv = counter_priv(counter);
+	u32 psc;
+
+	if (!prescaler || prescaler > MAX_TIM_PSC + 1)
+		return -ERANGE;
+
+	psc = prescaler - 1;
+
+	return regmap_write(priv->regmap, TIM_PSC, psc);
+}
+
 static struct counter_comp stm32_count_ext[] = {
 	COUNTER_COMP_DIRECTION(stm32_count_direction_read),
 	COUNTER_COMP_ENABLE(stm32_count_enable_read, stm32_count_enable_write),
 	COUNTER_COMP_CEILING(stm32_count_ceiling_read,
 			     stm32_count_ceiling_write),
+	COUNTER_COMP_COUNT_U64("prescaler", stm32_count_prescaler_read,
+			       stm32_count_prescaler_write),
 };
 
 static const enum counter_synapse_action stm32_clock_synapse_actions[] = {
-- 
2.25.1