ftm-quaddec.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Flex Timer Module Quadrature decoder
 *
 * This module implements a driver for decoding the FTM quadrature
 * of ex. a LS1021A
 */

#include <linux/fsl/ftm.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/io.h>
#include <linux/mutex.h>
#include <linux/counter.h>
#include <linux/bitfield.h>

#define FTM_FIELD_UPDATE(ftm, offset, mask, val)			\
	({								\
		uint32_t flags;						\
		ftm_read(ftm, offset, &flags);				\
		flags &= ~mask;						\
		flags |= FIELD_PREP(mask, val);				\
		ftm_write(ftm, offset, flags);				\
	})

struct ftm_quaddec {
	struct counter_device counter;
	struct platform_device *pdev;
	void __iomem *ftm_base;
	bool big_endian;
	struct mutex ftm_quaddec_mutex;
};

static void ftm_read(struct ftm_quaddec *ftm, uint32_t offset, uint32_t *data)
{
	if (ftm->big_endian)
		*data = ioread32be(ftm->ftm_base + offset);
	else
		*data = ioread32(ftm->ftm_base + offset);
}

static void ftm_write(struct ftm_quaddec *ftm, uint32_t offset, uint32_t data)
{
	if (ftm->big_endian)
		iowrite32be(data, ftm->ftm_base + offset);
	else
		iowrite32(data, ftm->ftm_base + offset);
}

/* Hold mutex before modifying write protection state */
static void ftm_clear_write_protection(struct ftm_quaddec *ftm)
{
	uint32_t flag;

	/* First see if it is enabled */
	ftm_read(ftm, FTM_FMS, &flag);

	if (flag & FTM_FMS_WPEN)
		FTM_FIELD_UPDATE(ftm, FTM_MODE, FTM_MODE_WPDIS, 1);
}

static void ftm_set_write_protection(struct ftm_quaddec *ftm)
{
	FTM_FIELD_UPDATE(ftm, FTM_FMS, FTM_FMS_WPEN, 1);
}

static void ftm_reset_counter(struct ftm_quaddec *ftm)
{
	/* Reset hardware counter to CNTIN */
	ftm_write(ftm, FTM_CNT, 0x0);
}

static void ftm_quaddec_init(struct ftm_quaddec *ftm)
{
	ftm_clear_write_protection(ftm);

	/*
	 * Do not write in the region from the CNTIN register through the
	 * PWMLOAD register when FTMEN = 0.
	 * Also reset other fields to zero
	 */
	ftm_write(ftm, FTM_MODE, FTM_MODE_FTMEN);
	ftm_write(ftm, FTM_CNTIN, 0x0000);
	ftm_write(ftm, FTM_MOD, 0xffff);
	ftm_write(ftm, FTM_CNT, 0x0);
	/* Set prescaler, reset other fields to zero */
	ftm_write(ftm, FTM_SC, FTM_SC_PS_1);

	/* Select quad mode, reset other fields to zero */
	ftm_write(ftm, FTM_QDCTRL, FTM_QDCTRL_QUADEN);

	/* Unused features and reset to default section */
	ftm_write(ftm, FTM_POL, 0x0);
	ftm_write(ftm, FTM_FLTCTRL, 0x0);
	ftm_write(ftm, FTM_SYNCONF, 0x0);
	ftm_write(ftm, FTM_SYNC, 0xffff);

	/* Lock the FTM */
	ftm_set_write_protection(ftm);
}

static void ftm_quaddec_disable(void *ftm)
{
	struct ftm_quaddec *ftm_qua = ftm;

	ftm_clear_write_protection(ftm_qua);
	ftm_write(ftm_qua, FTM_MODE, 0);
	ftm_write(ftm_qua, FTM_QDCTRL, 0);
	/*
	 * This is enough to disable the counter. No clock has been
	 * selected by writing to FTM_SC in init()
	 */
	ftm_set_write_protection(ftm_qua);
}

static int ftm_quaddec_get_prescaler(struct counter_device *counter,
				     struct counter_count *count,
				     size_t *cnt_mode)
{
	struct ftm_quaddec *ftm = counter->priv;
	uint32_t scflags;

	ftm_read(ftm, FTM_SC, &scflags);

	*cnt_mode = FIELD_GET(FTM_SC_PS_MASK, scflags);

	return 0;
}

static int ftm_quaddec_set_prescaler(struct counter_device *counter,
				     struct counter_count *count,
				     size_t cnt_mode)
{
	struct ftm_quaddec *ftm = counter->priv;

	mutex_lock(&ftm->ftm_quaddec_mutex);

	ftm_clear_write_protection(ftm);
	FTM_FIELD_UPDATE(ftm, FTM_SC, FTM_SC_PS_MASK, cnt_mode);
	ftm_set_write_protection(ftm);

	/* Also resets the counter as it is undefined anyway now */
	ftm_reset_counter(ftm);

	mutex_unlock(&ftm->ftm_quaddec_mutex);
	return 0;
}

static const char * const ftm_quaddec_prescaler[] = {
	"1", "2", "4", "8", "16", "32", "64", "128"
};

static struct counter_count_enum_ext ftm_quaddec_prescaler_enum = {
	.items = ftm_quaddec_prescaler,
	.num_items = ARRAY_SIZE(ftm_quaddec_prescaler),
	.get = ftm_quaddec_get_prescaler,
	.set = ftm_quaddec_set_prescaler
};

enum ftm_quaddec_synapse_action {
	FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES,
};

static enum counter_synapse_action ftm_quaddec_synapse_actions[] = {
	[FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES] =
	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
};

enum ftm_quaddec_count_function {
	FTM_QUADDEC_COUNT_ENCODER_MODE_1,
};

static const enum counter_count_function ftm_quaddec_count_functions[] = {
	[FTM_QUADDEC_COUNT_ENCODER_MODE_1] =
	COUNTER_COUNT_FUNCTION_QUADRATURE_X4
};

static int ftm_quaddec_count_read(struct counter_device *counter,
				  struct counter_count *count,
				  struct counter_count_read_value *val)
{
	struct ftm_quaddec *const ftm = counter->priv;
	uint32_t cntval;

	ftm_read(ftm, FTM_CNT, &cntval);

	counter_count_read_value_set(val, COUNTER_COUNT_POSITION, &cntval);

	return 0;
}

static int ftm_quaddec_count_write(struct counter_device *counter,
				   struct counter_count *count,
				   struct counter_count_write_value *val)
{
	struct ftm_quaddec *const ftm = counter->priv;
	u32 cnt;
	int err;

	err = counter_count_write_value_get(&cnt, COUNTER_COUNT_POSITION, val);
	if (err)
		return err;

	if (cnt != 0) {
		dev_warn(&ftm->pdev->dev, "Can only accept '0' as new counter value\n");
		return -EINVAL;
	}

	ftm_reset_counter(ftm);

	return 0;
}

static int ftm_quaddec_count_function_get(struct counter_device *counter,
					  struct counter_count *count,
					  size_t *function)
{
	*function = FTM_QUADDEC_COUNT_ENCODER_MODE_1;

	return 0;
}

static int ftm_quaddec_action_get(struct counter_device *counter,
				  struct counter_count *count,
				  struct counter_synapse *synapse,
				  size_t *action)
{
	*action = FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES;

	return 0;
}

static const struct counter_ops ftm_quaddec_cnt_ops = {
	.count_read = ftm_quaddec_count_read,
	.count_write = ftm_quaddec_count_write,
	.function_get = ftm_quaddec_count_function_get,
	.action_get = ftm_quaddec_action_get,
};

static struct counter_signal ftm_quaddec_signals[] = {
	{
		.id = 0,
		.name = "Channel 1 Phase A"
	},
	{
		.id = 1,
		.name = "Channel 1 Phase B"
	}
};

static struct counter_synapse ftm_quaddec_count_synapses[] = {
	{
		.actions_list = ftm_quaddec_synapse_actions,
		.num_actions = ARRAY_SIZE(ftm_quaddec_synapse_actions),
		.signal = &ftm_quaddec_signals[0]
	},
	{
		.actions_list = ftm_quaddec_synapse_actions,
		.num_actions = ARRAY_SIZE(ftm_quaddec_synapse_actions),
		.signal = &ftm_quaddec_signals[1]
	}
};

static const struct counter_count_ext ftm_quaddec_count_ext[] = {
	COUNTER_COUNT_ENUM("prescaler", &ftm_quaddec_prescaler_enum),
	COUNTER_COUNT_ENUM_AVAILABLE("prescaler", &ftm_quaddec_prescaler_enum),
};

static struct counter_count ftm_quaddec_counts = {
	.id = 0,
	.name = "Channel 1 Count",
	.functions_list = ftm_quaddec_count_functions,
	.num_functions = ARRAY_SIZE(ftm_quaddec_count_functions),
	.synapses = ftm_quaddec_count_synapses,
	.num_synapses = ARRAY_SIZE(ftm_quaddec_count_synapses),
	.ext = ftm_quaddec_count_ext,
	.num_ext = ARRAY_SIZE(ftm_quaddec_count_ext)
};

static int ftm_quaddec_probe(struct platform_device *pdev)
{
	struct ftm_quaddec *ftm;

	struct device_node *node = pdev->dev.of_node;
	struct resource *io;
	int ret;

	ftm = devm_kzalloc(&pdev->dev, sizeof(*ftm), GFP_KERNEL);
	if (!ftm)
		return -ENOMEM;

	platform_set_drvdata(pdev, ftm);

	io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!io) {
		dev_err(&pdev->dev, "Failed to get memory region\n");
		return -ENODEV;
	}

	ftm->pdev = pdev;
	ftm->big_endian = of_property_read_bool(node, "big-endian");
	ftm->ftm_base = devm_ioremap(&pdev->dev, io->start, resource_size(io));

	if (!ftm->ftm_base) {
		dev_err(&pdev->dev, "Failed to map memory region\n");
		return -EINVAL;
	}
	ftm->counter.name = dev_name(&pdev->dev);
	ftm->counter.parent = &pdev->dev;
	ftm->counter.ops = &ftm_quaddec_cnt_ops;
	ftm->counter.counts = &ftm_quaddec_counts;
	ftm->counter.num_counts = 1;
	ftm->counter.signals = ftm_quaddec_signals;
	ftm->counter.num_signals = ARRAY_SIZE(ftm_quaddec_signals);
	ftm->counter.priv = ftm;

	mutex_init(&ftm->ftm_quaddec_mutex);

	ftm_quaddec_init(ftm);

	ret = devm_add_action_or_reset(&pdev->dev, ftm_quaddec_disable, ftm);
	if (ret)
		return ret;

	ret = devm_counter_register(&pdev->dev, &ftm->counter);
	if (ret)
		return ret;

	return 0;
}

static const struct of_device_id ftm_quaddec_match[] = {
	{ .compatible = "fsl,ftm-quaddec" },
	{},
};

static struct platform_driver ftm_quaddec_driver = {
	.driver = {
		.name = "ftm-quaddec",
		.of_match_table = ftm_quaddec_match,
	},
	.probe = ftm_quaddec_probe,
};

module_platform_driver(ftm_quaddec_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kjeld Flarup <kfa@deif.com>");
MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");