counter: stm32-timer-cnt: Report count function when SLAVE_MODE_DISABLED

When in SLAVE_MODE_DISABLED mode, the count still increases if the
counter is enabled because an internal clock is used. This patch fixes
the stm32_count_function_get() and stm32_count_function_set() functions
to properly handle this behavior.

Fixes: ad29937 ("counter: Add STM32 Timer quadrature encoder")
Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20210226012931.161429-1-vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/counter/stm32-timer-cnt.c

@@ -44,13 +44,14 @@ struct stm32_timer_cnt {
  * @STM32_COUNT_ENCODER_MODE_3: counts on both TI1FP1 and TI2FP2 edges
  */
 enum stm32_count_function {
-	STM32_COUNT_SLAVE_MODE_DISABLED = -1,
+	STM32_COUNT_SLAVE_MODE_DISABLED,
 	STM32_COUNT_ENCODER_MODE_1,
 	STM32_COUNT_ENCODER_MODE_2,
 	STM32_COUNT_ENCODER_MODE_3,
 };
 
 static enum counter_count_function stm32_count_functions[] = {
+	[STM32_COUNT_SLAVE_MODE_DISABLED] = COUNTER_COUNT_FUNCTION_INCREASE,
 	[STM32_COUNT_ENCODER_MODE_1] = COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
 	[STM32_COUNT_ENCODER_MODE_2] = COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B,
 	[STM32_COUNT_ENCODER_MODE_3] = COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
@@ -90,6 +91,9 @@ static int stm32_count_function_get(struct counter_device *counter,
 	regmap_read(priv->regmap, TIM_SMCR, &smcr);
 
 	switch (smcr & TIM_SMCR_SMS) {
+	case 0:
+		*function = STM32_COUNT_SLAVE_MODE_DISABLED;
+		return 0;
 	case 1:
 		*function = STM32_COUNT_ENCODER_MODE_1;
 		return 0;
@@ -99,9 +103,9 @@ static int stm32_count_function_get(struct counter_device *counter,
 	case 3:
 		*function = STM32_COUNT_ENCODER_MODE_3;
 		return 0;
+	default:
+		return -EINVAL;
 	}
-
-	return -EINVAL;
 }
 
 static int stm32_count_function_set(struct counter_device *counter,
@@ -112,6 +116,9 @@ static int stm32_count_function_set(struct counter_device *counter,
 	u32 cr1, sms;
 
 	switch (function) {
+	case STM32_COUNT_SLAVE_MODE_DISABLED:
+		sms = 0;
+		break;
 	case STM32_COUNT_ENCODER_MODE_1:
 		sms = 1;
 		break;
@@ -122,8 +129,7 @@ static int stm32_count_function_set(struct counter_device *counter,
 		sms = 3;
 		break;
 	default:
-		sms = 0;
-		break;
+		return -EINVAL;
 	}
 
 	/* Store enable status */
@@ -274,31 +280,36 @@ static int stm32_action_get(struct counter_device *counter,
 	size_t function;
 	int err;
 
-	/* Default action mode (e.g. STM32_COUNT_SLAVE_MODE_DISABLED) */
-	*action = STM32_SYNAPSE_ACTION_NONE;
-
 	err = stm32_count_function_get(counter, count, &function);
 	if (err)
-		return 0;
+		return err;
 
 	switch (function) {
+	case STM32_COUNT_SLAVE_MODE_DISABLED:
+		/* counts on internal clock when CEN=1 */
+		*action = STM32_SYNAPSE_ACTION_NONE;
+		return 0;
 	case STM32_COUNT_ENCODER_MODE_1:
 		/* counts up/down on TI1FP1 edge depending on TI2FP2 level */
 		if (synapse->signal->id == count->synapses[0].signal->id)
 			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
-		break;
+		else
+			*action = STM32_SYNAPSE_ACTION_NONE;
+		return 0;
 	case STM32_COUNT_ENCODER_MODE_2:
 		/* counts up/down on TI2FP2 edge depending on TI1FP1 level */
 		if (synapse->signal->id == count->synapses[1].signal->id)
 			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
-		break;
+		else
+			*action = STM32_SYNAPSE_ACTION_NONE;
+		return 0;
 	case STM32_COUNT_ENCODER_MODE_3:
 		/* counts up/down on both TI1FP1 and TI2FP2 edges */
 		*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
-		break;
+		return 0;
+	default:
+		return -EINVAL;
 	}
-
-	return 0;
 }
 
 static const struct counter_ops stm32_timer_cnt_ops = {