[PATCH 7/8] counter/ti-eqep: add support for edge capture unit

[David Lechner <david@lechnology.com>]

This adds support for the Edge Capture Unit to the TI eQEP counter
driver. This just adds the minimum required features to measure speed
using the Unit Timer and the Edge Capture unit. Additional features can
be added in the future if needed.

This adds 4 new device-level attributes:
- edge_capture_unit_prescaler: selects a prescalar for the Counter count
	coming into the Edge Capture Unit
- edge_capture_unit_max_period: selects the max time period that can be
	measured by the Edge Capture Unit
- edge_capture_unit_latched_period: gets the period that was measured
	when the event selected by the latch_mode attribute is triggered
- edge_capture_unit_enable: enables or disables the Edge Capture Unit

Signed-off-by: David Lechner <david@lechnology.com>
---
 drivers/counter/ti-eqep.c | 150 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)

diff --git a/drivers/counter/ti-eqep.c b/drivers/counter/ti-eqep.c
index ef899655ad1d..fb1f4d0b4cde 100644
--- a/drivers/counter/ti-eqep.c
+++ b/drivers/counter/ti-eqep.c
@@ -116,6 +116,12 @@
 #define QEPSTS_FIMF		BIT(1)
 #define QEPSTS_PCEF		BIT(0)
 
+#define QCAPCTL_CEN		BIT(15)
+#define QCAPCTL_CCPS_SHIFT	4
+#define QCAPCTL_CCPS		GENMASK(6, 4)
+#define QCAPCTL_UPPS_SHIFT	0
+#define QCAPCTL_UPPS		GENMASK(3, 0)
+
 /* EQEP Inputs */
 enum {
 	TI_EQEP_SIGNAL_QEPA,	/* QEPA/XCLK */
@@ -479,6 +485,137 @@ static struct counter_count ti_eqep_counts[] = {
 	},
 };
 
+static int ti_eqep_edge_capture_unit_enable_read(struct counter_device *counter,
+						 u8 *value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qcapctl;
+
+	regmap_read(priv->regmap16, QCAPCTL, &qcapctl);
+	*value = !!(qcapctl & QCAPCTL_CEN);
+
+	return 0;
+}
+
+static int ti_eqep_edge_capture_unit_enable_write(struct counter_device *counter,
+						  u8 value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+
+	if (value)
+		regmap_set_bits(priv->regmap16, QCAPCTL, QCAPCTL_CEN);
+	else
+		regmap_clear_bits(priv->regmap16, QCAPCTL, QCAPCTL_CEN);
+
+	return 0;
+}
+
+static int
+ti_eqep_edge_capture_unit_latched_period_read(struct counter_device *counter,
+					      u64 *value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qcprdlat, qcapctl;
+	u8 ccps;
+
+	regmap_read(priv->regmap16, QCPRDLAT, &qcprdlat);
+	regmap_read(priv->regmap16, QCAPCTL, &qcapctl);
+	ccps = (qcapctl & QCAPCTL_CCPS) >> QCAPCTL_CCPS_SHIFT;
+
+	/* convert timer ticks to nanoseconds */
+	*value = mul_u64_u32_div(qcprdlat << ccps, NSEC_PER_SEC, priv->sysclkout_rate);
+
+	return 0;
+}
+
+static int
+ti_eqep_edge_capture_unit_max_period_read(struct counter_device *counter,
+					  u64 *value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qcapctl;
+	u8 ccps;
+
+	regmap_read(priv->regmap16, QCAPCTL, &qcapctl);
+	ccps = (qcapctl & QCAPCTL_CCPS) >> QCAPCTL_CCPS_SHIFT;
+
+	/* convert timer ticks to nanoseconds */
+	*value = mul_u64_u32_div(USHRT_MAX << ccps, NSEC_PER_SEC,
+				 priv->sysclkout_rate);
+
+	return 0;
+}
+
+static int
+ti_eqep_edge_capture_unit_max_period_write(struct counter_device *counter,
+					   u64 value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 period;
+	u8 ccps;
+
+	/* convert nanoseconds to timer ticks */
+	period = value = mul_u64_u32_div(value, priv->sysclkout_rate, NSEC_PER_SEC);
+	if (period != value)
+		return -ERANGE;
+
+	/* find the smallest divider that will fit the requested period */
+	for (ccps = 0; ccps <= 7; ccps++)
+		if (USHRT_MAX << ccps >= period)
+			break;
+
+	if (ccps > 7)
+		return -EINVAL;
+
+	regmap_write_bits(priv->regmap16, QCAPCTL, QCAPCTL_CCPS,
+			  ccps << QCAPCTL_CCPS_SHIFT);
+
+	return 0;
+}
+
+static int
+ti_eqep_edge_capture_unit_prescaler_read(struct counter_device *counter,
+					 u32 *value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qcapctl;
+
+	regmap_read(priv->regmap16, QCAPCTL, &qcapctl);
+	*value = (qcapctl & QCAPCTL_UPPS) >> QCAPCTL_UPPS_SHIFT;
+
+	return 0;
+}
+
+static int
+ti_eqep_edge_capture_unit_prescaler_write(struct counter_device *counter,
+					  u32 value)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+
+	regmap_write_bits(priv->regmap16, QCAPCTL, QCAPCTL_UPPS,
+			  value << QCAPCTL_UPPS_SHIFT);
+
+	return 0;
+}
+
+static const char *const ti_eqep_edge_capture_unit_prescaler_values[] = {
+	"1",
+	"2",
+	"4",
+	"8",
+	"16",
+	"32",
+	"64",
+	"128",
+	"256",
+	"512",
+	"1024",
+	"2048",
+};
+
+static DEFINE_COUNTER_ENUM(ti_eqep_edge_capture_unit_prescaler_available,
+			   ti_eqep_edge_capture_unit_prescaler_values);
+
 static int ti_eqep_latch_mode_read(struct counter_device *counter,
 					    u32 *value)
 {
@@ -601,6 +738,19 @@ static int ti_eqep_unit_timer_enable_write(struct counter_device *counter,
 }
 
 static struct counter_comp ti_eqep_device_ext[] = {
+	COUNTER_COMP_DEVICE_BOOL("edge_capture_unit_enable",
+				 ti_eqep_edge_capture_unit_enable_read,
+				 ti_eqep_edge_capture_unit_enable_write),
+	COUNTER_COMP_DEVICE_U64("edge_capture_unit_latched_period",
+				ti_eqep_edge_capture_unit_latched_period_read,
+				NULL),
+	COUNTER_COMP_DEVICE_U64("edge_capture_unit_max_period",
+				ti_eqep_edge_capture_unit_max_period_read,
+				ti_eqep_edge_capture_unit_max_period_write),
+	COUNTER_COMP_DEVICE_ENUM("edge_capture_unit_prescaler",
+				 ti_eqep_edge_capture_unit_prescaler_read,
+				 ti_eqep_edge_capture_unit_prescaler_write,
+				 ti_eqep_edge_capture_unit_prescaler_available),
 	COUNTER_COMP_DEVICE_ENUM("latch_mode", ti_eqep_latch_mode_read,
 				ti_eqep_latch_mode_write, ti_eqep_latch_modes),
 	COUNTER_COMP_DEVICE_U64("unit_timer_time", ti_eqep_unit_timer_time_read,
-- 
2.25.1