[PATCH v3 3/6] counter: new TI eQEP driver

[David Lechner <david@lechnology.com>]

This adds a new counter driver for the Texas Instruments Enhanced
Quadrature Encoder Pulse (eQEP) module.

Only very basic functionality is currently implemented - only enough to
be able to read the position. The actual device has many more features
which can be added to the driver on an as-needed basis.

It is not possible to read the QEPA/B signal values in hardware, so
that feature is omitted.

The TI_PWMSS kernel option is selected in Kconfig to enable the parent
bus, which is needed for power management.

Signed-off-by: David Lechner <david@lechnology.com>
---

v3 changes:
- Fixed ordering of pm runtime disable
- Added comment explaining where pm runtime is handled
- Dropped initialization of .action in ti_eqep_position_synapses
v2 changes:
- Dropped unused index and strobe signals
- Added synapses and actions
- Fixed base in of kstrtouint()
- Clarifications in commit message


 MAINTAINERS               |   6 +
 drivers/bus/Kconfig       |   2 +-
 drivers/counter/Kconfig   |  11 +
 drivers/counter/Makefile  |   1 +
 drivers/counter/ti-eqep.c | 473 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 492 insertions(+), 1 deletion(-)
 create mode 100644 drivers/counter/ti-eqep.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 783569e3c4b4..53c28d52964c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16014,6 +16014,12 @@ S:	Maintained
 F:	drivers/media/platform/davinci/
 F:	include/media/davinci/
 
+TI ENHANCED QUADRATURE ENCODER PULSE (eQEP) DRIVER
+R:	David Lechner <david@lechnology.com>
+L:	linux-iio@vger.kernel.org
+F:	Documentation/devicetree/bindings/counter/ti-eqep.yaml
+F:	drivers/counter/ti-eqep.c
+
 TI ETHERNET SWITCH DRIVER (CPSW)
 R:	Grygorii Strashko <grygorii.strashko@ti.com>
 L:	linux-omap@vger.kernel.org
diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index 4eeb15839ce0..04db7fce4604 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -142,7 +142,7 @@ config TEGRA_GMI
 
 config  TI_PWMSS
 	bool
-	default y if (ARCH_OMAP2PLUS) && (PWM_TIECAP || PWM_TIEHRPWM)
+	default y if (ARCH_OMAP2PLUS) && (PWM_TIECAP || PWM_TIEHRPWM || TI_EQEP)
 	help
 	  PWM Subsystem driver support for AM33xx SOC.
 
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 2967d0a9ff91..c80fa76bb531 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -49,6 +49,17 @@ config STM32_LPTIMER_CNT
 	  To compile this driver as a module, choose M here: the
 	  module will be called stm32-lptimer-cnt.
 
+config TI_EQEP
+	tristate "TI eQEP counter driver"
+	depends on (SOC_AM33XX || COMPILE_TEST)
+	select REGMAP_MMIO
+	help
+	  Select this option to enable the Texas Instruments Enhanced Quadrature
+	  Encoder Pulse (eQEP) counter driver.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ti-eqep.
+
 config FTM_QUADDEC
 	tristate "Flex Timer Module Quadrature decoder driver"
 	depends on HAS_IOMEM && OF
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index 40d35522937d..55142d1f4c43 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -8,4 +8,5 @@ obj-$(CONFIG_COUNTER) += counter.o
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
+obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
 obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
diff --git a/drivers/counter/ti-eqep.c b/drivers/counter/ti-eqep.c
new file mode 100644
index 000000000000..4b3ef2449c06
--- /dev/null
+++ b/drivers/counter/ti-eqep.c
@@ -0,0 +1,473 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 David Lechner <david@lechnology.com>
+ *
+ * Counter driver for Texas Instruments Enhanced Quadrature Encoder Pulse (eQEP)
+ */
+
+#include <linux/bitops.h>
+#include <linux/counter.h>
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+
+/* 32-bit registers */
+#define QPOSCNT		0x0
+#define QPOSINIT	0x4
+#define QPOSMAX		0x8
+#define QPOSCMP		0xc
+#define QPOSILAT	0x10
+#define QPOSSLAT	0x14
+#define QPOSLAT		0x18
+#define QUTMR		0x1c
+#define QUPRD		0x20
+
+/* 16-bit registers */
+#define QWDTMR		0x0	/* 0x24 */
+#define QWDPRD		0x2	/* 0x26 */
+#define QDECCTL		0x4	/* 0x28 */
+#define QEPCTL		0x6	/* 0x2a */
+#define QCAPCTL		0x8	/* 0x2c */
+#define QPOSCTL		0xa	/* 0x2e */
+#define QEINT		0xc	/* 0x30 */
+#define QFLG		0xe	/* 0x32 */
+#define QCLR		0x10	/* 0x34 */
+#define QFRC		0x12	/* 0x36 */
+#define QEPSTS		0x14	/* 0x38 */
+#define QCTMR		0x16	/* 0x3a */
+#define QCPRD		0x18	/* 0x3c */
+#define QCTMRLAT	0x1a	/* 0x3e */
+#define QCPRDLAT	0x1c	/* 0x40 */
+
+#define QDECCTL_QSRC_SHIFT	14
+#define QDECCTL_QSRC		GENMASK(15, 14)
+#define QDECCTL_SOEN		BIT(13)
+#define QDECCTL_SPSEL		BIT(12)
+#define QDECCTL_XCR		BIT(11)
+#define QDECCTL_SWAP		BIT(10)
+#define QDECCTL_IGATE		BIT(9)
+#define QDECCTL_QAP		BIT(8)
+#define QDECCTL_QBP		BIT(7)
+#define QDECCTL_QIP		BIT(6)
+#define QDECCTL_QSP		BIT(5)
+
+#define QEPCTL_FREE_SOFT	GENMASK(15, 14)
+#define QEPCTL_PCRM		GENMASK(13, 12)
+#define QEPCTL_SEI		GENMASK(11, 10)
+#define QEPCTL_IEI		GENMASK(9, 8)
+#define QEPCTL_SWI		BIT(7)
+#define QEPCTL_SEL		BIT(6)
+#define QEPCTL_IEL		GENMASK(5, 4)
+#define QEPCTL_PHEN		BIT(3)
+#define QEPCTL_QCLM		BIT(2)
+#define QEPCTL_UTE		BIT(1)
+#define QEPCTL_WDE		BIT(0)
+
+/* EQEP Inputs */
+enum {
+	TI_EQEP_SIGNAL_QEPA,	/* QEPA/XCLK */
+	TI_EQEP_SIGNAL_QEPB,	/* QEPB/XDIR */
+};
+
+/* Position Counter Input Modes */
+enum {
+	TI_EQEP_COUNT_FUNC_QUAD_COUNT,
+	TI_EQEP_COUNT_FUNC_DIR_COUNT,
+	TI_EQEP_COUNT_FUNC_UP_COUNT,
+	TI_EQEP_COUNT_FUNC_DOWN_COUNT,
+};
+
+enum {
+	TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES,
+	TI_EQEP_SYNAPSE_ACTION_RISING_EDGE,
+	TI_EQEP_SYNAPSE_ACTION_NONE,
+};
+
+struct ti_eqep_cnt {
+	struct counter_device counter;
+	struct regmap *regmap32;
+	struct regmap *regmap16;
+};
+
+static int ti_eqep_count_read(struct counter_device *counter,
+			      struct counter_count *count,
+			      struct counter_count_read_value *val)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 cnt;
+
+	regmap_read(priv->regmap32, QPOSCNT, &cnt);
+	counter_count_read_value_set(val, COUNTER_COUNT_POSITION, &cnt);
+
+	return 0;
+}
+
+static int ti_eqep_count_write(struct counter_device *counter,
+			       struct counter_count *count,
+			       struct counter_count_write_value *val)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 cnt, max;
+	int err;
+
+	err = counter_count_write_value_get(&cnt, COUNTER_COUNT_POSITION, val);
+	if (err)
+		return err;
+
+	regmap_read(priv->regmap32, QPOSMAX, &max);
+	if (cnt > max)
+		return -EINVAL;
+
+	return regmap_write(priv->regmap32, QPOSCNT, cnt);
+}
+
+static int ti_eqep_function_get(struct counter_device *counter,
+				struct counter_count *count, size_t *function)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qdecctl;
+
+	regmap_read(priv->regmap16, QDECCTL, &qdecctl);
+	*function = (qdecctl & QDECCTL_QSRC) >> QDECCTL_QSRC_SHIFT;
+
+	return 0;
+}
+
+static int ti_eqep_function_set(struct counter_device *counter,
+				struct counter_count *count, size_t function)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+
+	return regmap_write_bits(priv->regmap16, QDECCTL, QDECCTL_QSRC,
+				 function << QDECCTL_QSRC_SHIFT);
+}
+
+static int ti_eqep_action_get(struct counter_device *counter,
+			      struct counter_count *count,
+			      struct counter_synapse *synapse, size_t *action)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	size_t function;
+	u32 qdecctl;
+	int err;
+
+	err = ti_eqep_function_get(counter, count, &function);
+	if (err)
+		return err;
+
+	switch (function) {
+	case TI_EQEP_COUNT_FUNC_QUAD_COUNT:
+		/* In quadrature mode, the rising and falling edge of both
+		 * QEPA and QEPB trigger QCLK.
+		 */
+		*action = TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	case TI_EQEP_COUNT_FUNC_DIR_COUNT:
+		/* In direction-count mode only rising edge of QEPA is counted
+		 * and QEPB gives direction.
+		 */
+		switch (synapse->signal->id) {
+		case TI_EQEP_SIGNAL_QEPA:
+			*action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
+			break;
+		default:
+			*action = TI_EQEP_SYNAPSE_ACTION_NONE;
+			break;
+		}
+		break;
+	case TI_EQEP_COUNT_FUNC_UP_COUNT:
+	case TI_EQEP_COUNT_FUNC_DOWN_COUNT:
+		/* In up/down-count modes only QEPA is counted and QEPB is not
+		 * used.
+		 */
+		switch (synapse->signal->id) {
+		case TI_EQEP_SIGNAL_QEPA:
+			err = regmap_read(priv->regmap16, QDECCTL, &qdecctl);
+			if (err)
+				return err;
+
+			if (qdecctl & QDECCTL_XCR)
+				*action = TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES;
+			else
+				*action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
+			break;
+		default:
+			*action = TI_EQEP_SYNAPSE_ACTION_NONE;
+			break;
+		}
+		break;
+	}
+
+	return 0;
+}
+
+static const struct counter_ops ti_eqep_counter_ops = {
+	.count_read	= ti_eqep_count_read,
+	.count_write	= ti_eqep_count_write,
+	.function_get	= ti_eqep_function_get,
+	.function_set	= ti_eqep_function_set,
+	.action_get	= ti_eqep_action_get,
+};
+
+static ssize_t ti_eqep_position_ceiling_read(struct counter_device *counter,
+					     struct counter_count *count,
+					     void *ext_priv, char *buf)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qposmax;
+
+	regmap_read(priv->regmap32, QPOSMAX, &qposmax);
+
+	return sprintf(buf, "%u\n", qposmax);
+}
+
+static ssize_t ti_eqep_position_ceiling_write(struct counter_device *counter,
+					      struct counter_count *count,
+					      void *ext_priv, const char *buf,
+					      size_t len)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	int err;
+	u32 res;
+
+	err = kstrtouint(buf, 0, &res);
+	if (err < 0)
+		return err;
+
+	regmap_write(priv->regmap32, QPOSMAX, res);
+
+	return len;
+}
+
+static ssize_t ti_eqep_position_floor_read(struct counter_device *counter,
+					   struct counter_count *count,
+					   void *ext_priv, char *buf)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qposinit;
+
+	regmap_read(priv->regmap32, QPOSINIT, &qposinit);
+
+	return sprintf(buf, "%u\n", qposinit);
+}
+
+static ssize_t ti_eqep_position_floor_write(struct counter_device *counter,
+					    struct counter_count *count,
+					    void *ext_priv, const char *buf,
+					    size_t len)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	int err;
+	u32 res;
+
+	err = kstrtouint(buf, 0, &res);
+	if (err < 0)
+		return err;
+
+	regmap_write(priv->regmap32, QPOSINIT, res);
+
+	return len;
+}
+
+static ssize_t ti_eqep_position_enable_read(struct counter_device *counter,
+					    struct counter_count *count,
+					    void *ext_priv, char *buf)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	u32 qepctl;
+
+	regmap_read(priv->regmap16, QEPCTL, &qepctl);
+
+	return sprintf(buf, "%u\n", !!(qepctl & QEPCTL_PHEN));
+}
+
+static ssize_t ti_eqep_position_enable_write(struct counter_device *counter,
+					     struct counter_count *count,
+					     void *ext_priv, const char *buf,
+					     size_t len)
+{
+	struct ti_eqep_cnt *priv = counter->priv;
+	int err;
+	bool res;
+
+	err = kstrtobool(buf, &res);
+	if (err < 0)
+		return err;
+
+	regmap_write_bits(priv->regmap16, QEPCTL, QEPCTL_PHEN, res ? -1 : 0);
+
+	return len;
+}
+
+static struct counter_count_ext ti_eqep_position_ext[] = {
+	{
+		.name	= "ceiling",
+		.read	= ti_eqep_position_ceiling_read,
+		.write	= ti_eqep_position_ceiling_write,
+	},
+	{
+		.name	= "floor",
+		.read	= ti_eqep_position_floor_read,
+		.write	= ti_eqep_position_floor_write,
+	},
+	{
+		.name	= "enable",
+		.read	= ti_eqep_position_enable_read,
+		.write	= ti_eqep_position_enable_write,
+	},
+};
+
+static struct counter_signal ti_eqep_signals[] = {
+	[TI_EQEP_SIGNAL_QEPA] = {
+		.id = TI_EQEP_SIGNAL_QEPA,
+		.name = "QEPA"
+	},
+	[TI_EQEP_SIGNAL_QEPB] = {
+		.id = TI_EQEP_SIGNAL_QEPB,
+		.name = "QEPB"
+	},
+};
+
+static const enum counter_count_function ti_eqep_position_functions[] = {
+	[TI_EQEP_COUNT_FUNC_QUAD_COUNT]	= COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
+	[TI_EQEP_COUNT_FUNC_DIR_COUNT]	= COUNTER_COUNT_FUNCTION_PULSE_DIRECTION,
+	[TI_EQEP_COUNT_FUNC_UP_COUNT]	= COUNTER_COUNT_FUNCTION_INCREASE,
+	[TI_EQEP_COUNT_FUNC_DOWN_COUNT]	= COUNTER_COUNT_FUNCTION_DECREASE,
+};
+
+static const enum counter_synapse_action ti_eqep_position_synapse_actions[] = {
+	[TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES]	= COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
+	[TI_EQEP_SYNAPSE_ACTION_RISING_EDGE]	= COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+	[TI_EQEP_SYNAPSE_ACTION_NONE]		= COUNTER_SYNAPSE_ACTION_NONE,
+};
+
+static struct counter_synapse ti_eqep_position_synapses[] = {
+	{
+		.actions_list	= ti_eqep_position_synapse_actions,
+		.num_actions	= ARRAY_SIZE(ti_eqep_position_synapse_actions),
+		.signal		= &ti_eqep_signals[TI_EQEP_SIGNAL_QEPA],
+	},
+	{
+		.actions_list	= ti_eqep_position_synapse_actions,
+		.num_actions	= ARRAY_SIZE(ti_eqep_position_synapse_actions),
+		.signal		= &ti_eqep_signals[TI_EQEP_SIGNAL_QEPB],
+	},
+};
+
+static struct counter_count ti_eqep_counts[] = {
+	{
+		.id		= 0,
+		.name		= "QPOSCNT",
+		.functions_list	= ti_eqep_position_functions,
+		.num_functions	= ARRAY_SIZE(ti_eqep_position_functions),
+		.synapses	= ti_eqep_position_synapses,
+		.num_synapses	= ARRAY_SIZE(ti_eqep_position_synapses),
+		.ext		= ti_eqep_position_ext,
+		.num_ext	= ARRAY_SIZE(ti_eqep_position_ext),
+	},
+};
+
+static const struct regmap_config ti_eqep_regmap32_config = {
+	.name = "32-bit",
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.max_register = 0x24,
+};
+
+static const struct regmap_config ti_eqep_regmap16_config = {
+	.name = "16-bit",
+	.reg_bits = 16,
+	.val_bits = 16,
+	.reg_stride = 2,
+	.max_register = 0x1e,
+};
+
+static int ti_eqep_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ti_eqep_cnt *priv;
+	void __iomem *base;
+	int err;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	priv->regmap32 = devm_regmap_init_mmio(dev, base,
+					       &ti_eqep_regmap32_config);
+	if (IS_ERR(priv->regmap32))
+		return PTR_ERR(priv->regmap32);
+
+	priv->regmap16 = devm_regmap_init_mmio(dev, base + 0x24,
+					       &ti_eqep_regmap16_config);
+	if (IS_ERR(priv->regmap16))
+		return PTR_ERR(priv->regmap16);
+
+	priv->counter.name = dev_name(dev);
+	priv->counter.parent = dev;
+	priv->counter.ops = &ti_eqep_counter_ops;
+	priv->counter.counts = ti_eqep_counts;
+	priv->counter.num_counts = ARRAY_SIZE(ti_eqep_counts);
+	priv->counter.signals = ti_eqep_signals;
+	priv->counter.num_signals = ARRAY_SIZE(ti_eqep_signals);
+	priv->counter.priv = priv;
+
+	platform_set_drvdata(pdev, priv);
+
+	/*
+	 * Need to make sure power is turned on. On AM33xx, this comes from the
+	 * parent PWMSS bus driver. On AM17xx, this comes from the PSC power
+	 * domain.
+	 */
+	pm_runtime_enable(dev);
+	pm_runtime_get_sync(dev);
+
+	err = counter_register(&priv->counter);
+	if (err < 0) {
+		pm_runtime_put_sync(dev);
+		pm_runtime_disable(dev);
+		return err;
+	}
+
+	return 0;
+}
+
+static int ti_eqep_remove(struct platform_device *pdev)
+{
+	struct ti_eqep_cnt *priv = platform_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
+
+	counter_unregister(&priv->counter);
+	pm_runtime_put_sync(dev),
+	pm_runtime_disable(dev);
+
+	return 0;
+}
+
+static const struct of_device_id ti_eqep_of_match[] = {
+	{ .compatible = "ti,am3352-eqep", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ti_eqep_of_match);
+
+static struct platform_driver ti_eqep_driver = {
+	.probe = ti_eqep_probe,
+	.remove = ti_eqep_remove,
+	.driver = {
+		.name = "ti-eqep-cnt",
+		.of_match_table = ti_eqep_of_match,
+	},
+};
+module_platform_driver(ti_eqep_driver);
+
+MODULE_AUTHOR("David Lechner <david@lechnology.com>");
+MODULE_DESCRIPTION("TI eQEP counter driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1