counter: stm32-timer-cnt: Provide defines for slave mode selection

The STM32 timer permits configuration of the counter encoder mode via
the slave mode control register (SMCR) slave mode selection (SMS) bits.
This patch provides preprocessor defines for the supported encoder
modes.

Cc: Fabrice Gasnier <[e-mail]>
Signed-off-by: William Breathitt Gray <[e-mail]>
Reviewed-by: Fabrice Gasnier <[e-mail]>
Link: https://lore.kernel.org/r/ad3d[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/counter/stm32-timer-cnt.c

···
 	regmap_read(priv->regmap, TIM_SMCR, &smcr);
 
 	switch (smcr & TIM_SMCR_SMS) {
-	case 0:
+	case TIM_SMCR_SMS_SLAVE_MODE_DISABLED:
 		*function = STM32_COUNT_SLAVE_MODE_DISABLED;
 		return 0;
-	case 1:
+	case TIM_SMCR_SMS_ENCODER_MODE_1:
 		*function = STM32_COUNT_ENCODER_MODE_1;
 		return 0;
-	case 2:
+	case TIM_SMCR_SMS_ENCODER_MODE_2:
 		*function = STM32_COUNT_ENCODER_MODE_2;
 		return 0;
-	case 3:
+	case TIM_SMCR_SMS_ENCODER_MODE_3:
 		*function = STM32_COUNT_ENCODER_MODE_3;
 		return 0;
 	default:
···
 
 	switch (function) {
 	case STM32_COUNT_SLAVE_MODE_DISABLED:
-		sms = 0;
+		sms = TIM_SMCR_SMS_SLAVE_MODE_DISABLED;
 		break;
 	case STM32_COUNT_ENCODER_MODE_1:
-		sms = 1;
+		sms = TIM_SMCR_SMS_ENCODER_MODE_1;
 		break;
 	case STM32_COUNT_ENCODER_MODE_2:
-		sms = 2;
+		sms = TIM_SMCR_SMS_ENCODER_MODE_2;
 		break;
 	case STM32_COUNT_ENCODER_MODE_3:
-		sms = 3;
+		sms = TIM_SMCR_SMS_ENCODER_MODE_3;
 		break;
 	default:
 		return -EINVAL;

include/linux/mfd/stm32-timers.h

···
 #define MAX_TIM_ICPSC		0x3
 #define TIM_CR2_MMS_SHIFT	4
 #define TIM_CR2_MMS2_SHIFT	20
+#define TIM_SMCR_SMS_SLAVE_MODE_DISABLED	0 /* counts on internal clock when CEN=1 */
+#define TIM_SMCR_SMS_ENCODER_MODE_1		1 /* counts TI1FP1 edges, depending on TI2FP2 level */
+#define TIM_SMCR_SMS_ENCODER_MODE_2		2 /* counts TI2FP2 edges, depending on TI1FP1 level */
+#define TIM_SMCR_SMS_ENCODER_MODE_3		3 /* counts on both TI1FP1 and TI2FP2 edges */
 #define TIM_SMCR_TS_SHIFT	4
 #define TIM_BDTR_BKF_MASK	0xF
 #define TIM_BDTR_BKF_SHIFT(x)	(16 + (x) * 4)