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>
#include <linux/types.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 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, u32 *cnt_mode)
{
	struct ftm_quaddec *ftm = counter_priv(counter);
	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, u32 cnt_mode)
{
	struct ftm_quaddec *ftm = counter_priv(counter);

	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 const enum counter_synapse_action ftm_quaddec_synapse_actions[] = {
	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
};

static const enum counter_function ftm_quaddec_count_functions[] = {
	COUNTER_FUNCTION_QUADRATURE_X4
};

static int ftm_quaddec_count_read(struct counter_device *counter,
				  struct counter_count *count,
				  u64 *val)
{
	struct ftm_quaddec *const ftm = counter_priv(counter);
	uint32_t cntval;

	ftm_read(ftm, FTM_CNT, &cntval);

	*val = cntval;

	return 0;
}

static int ftm_quaddec_count_write(struct counter_device *counter,
				   struct counter_count *count,
				   const u64 val)
{
	struct ftm_quaddec *const ftm = counter_priv(counter);

	if (val != 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_read(struct counter_device *counter,
					   struct counter_count *count,
					   enum counter_function *function)
{
	*function = COUNTER_FUNCTION_QUADRATURE_X4;

	return 0;
}

static int ftm_quaddec_action_read(struct counter_device *counter,
				   struct counter_count *count,
				   struct counter_synapse *synapse,
				   enum counter_synapse_action *action)
{
	*action = COUNTER_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_read = ftm_quaddec_count_function_read,
	.action_read = ftm_quaddec_action_read,
};

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 DEFINE_COUNTER_ENUM(ftm_quaddec_prescaler_enum, ftm_quaddec_prescaler);

static struct counter_comp ftm_quaddec_count_ext[] = {
	COUNTER_COMP_COUNT_ENUM("prescaler", ftm_quaddec_get_prescaler,
				ftm_quaddec_set_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 counter_device *counter;
	struct ftm_quaddec *ftm;

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

	counter = devm_counter_alloc(&pdev->dev, sizeof(*ftm));
	if (!counter)
		return -ENOMEM;
	ftm = counter_priv(counter);

	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;
	}
	counter->name = dev_name(&pdev->dev);
	counter->parent = &pdev->dev;
	counter->ops = &ftm_quaddec_cnt_ops;
	counter->counts = &ftm_quaddec_counts;
	counter->num_counts = 1;
	counter->signals = ftm_quaddec_signals;
	counter->num_signals = ARRAY_SIZE(ftm_quaddec_signals);

	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_add(&pdev->dev, counter);
	if (ret)
		return dev_err_probe(&pdev->dev, ret, "Failed to add counter\n");

	return 0;
}

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

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_DESCRIPTION("Flex Timer Module Quadrature decoder");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kjeld Flarup <[email protected]>");
MODULE_AUTHOR("Patrick Havelange <[email protected]>");
MODULE_IMPORT_NS("COUNTER");