spi-offload-trigger-pwm.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2024 Analog Devices Inc.
  4 * Copyright (C) 2024 BayLibre, SAS
  5 *
  6 * Generic PWM trigger for SPI offload.
  7 */
  8
  9#include <linux/device.h>
 10#include <linux/err.h>
 11#include <linux/math.h>
 12#include <linux/mod_devicetable.h>
 13#include <linux/module.h>
 14#include <linux/platform_device.h>
 15#include <linux/property.h>
 16#include <linux/pwm.h>
 17#include <linux/spi/offload/provider.h>
 18#include <linux/spi/offload/types.h>
 19#include <linux/time.h>
 20#include <linux/types.h>
 21
 22struct spi_offload_trigger_pwm_state {
 23	struct device *dev;
 24	struct pwm_device *pwm;
 25};
 26
 27static bool spi_offload_trigger_pwm_match(struct spi_offload_trigger *trigger,
 28					  enum spi_offload_trigger_type type,
 29					  u64 *args, u32 nargs)
 30{
 31	if (nargs)
 32		return false;
 33
 34	return type == SPI_OFFLOAD_TRIGGER_PERIODIC;
 35}
 36
 37static int spi_offload_trigger_pwm_validate(struct spi_offload_trigger *trigger,
 38					    struct spi_offload_trigger_config *config)
 39{
 40	struct spi_offload_trigger_pwm_state *st = spi_offload_trigger_get_priv(trigger);
 41	struct spi_offload_trigger_periodic *periodic = &config->periodic;
 42	struct pwm_waveform wf = { };
 43	int ret;
 44
 45	if (config->type != SPI_OFFLOAD_TRIGGER_PERIODIC)
 46		return -EINVAL;
 47
 48	if (!periodic->frequency_hz)
 49		return -EINVAL;
 50
 51	wf.period_length_ns = DIV_ROUND_UP_ULL(NSEC_PER_SEC, periodic->frequency_hz);
 52	/* REVISIT: 50% duty-cycle for now - may add config parameter later */
 53	wf.duty_length_ns = wf.period_length_ns / 2;
 54	wf.duty_offset_ns = periodic->offset_ns;
 55
 56	ret = pwm_round_waveform_might_sleep(st->pwm, &wf);
 57	if (ret < 0)
 58		return ret;
 59
 60	periodic->frequency_hz = DIV_ROUND_UP_ULL(NSEC_PER_SEC, wf.period_length_ns);
 61	periodic->offset_ns = wf.duty_offset_ns;
 62
 63	return 0;
 64}
 65
 66static int spi_offload_trigger_pwm_enable(struct spi_offload_trigger *trigger,
 67					  struct spi_offload_trigger_config *config)
 68{
 69	struct spi_offload_trigger_pwm_state *st = spi_offload_trigger_get_priv(trigger);
 70	struct spi_offload_trigger_periodic *periodic = &config->periodic;
 71	struct pwm_waveform wf = { };
 72
 73	if (config->type != SPI_OFFLOAD_TRIGGER_PERIODIC)
 74		return -EINVAL;
 75
 76	if (!periodic->frequency_hz)
 77		return -EINVAL;
 78
 79	wf.period_length_ns = DIV_ROUND_UP_ULL(NSEC_PER_SEC, periodic->frequency_hz);
 80	/* REVISIT: 50% duty-cycle for now - may add config parameter later */
 81	wf.duty_length_ns = wf.period_length_ns / 2;
 82	wf.duty_offset_ns = periodic->offset_ns;
 83
 84	return pwm_set_waveform_might_sleep(st->pwm, &wf, false);
 85}
 86
 87static void spi_offload_trigger_pwm_disable(struct spi_offload_trigger *trigger)
 88{
 89	struct spi_offload_trigger_pwm_state *st = spi_offload_trigger_get_priv(trigger);
 90	struct pwm_waveform wf;
 91	int ret;
 92
 93	ret = pwm_get_waveform_might_sleep(st->pwm, &wf);
 94	if (ret < 0) {
 95		dev_err(st->dev, "failed to get waveform: %d\n", ret);
 96		return;
 97	}
 98
 99	wf.duty_length_ns = 0;
100
101	ret = pwm_set_waveform_might_sleep(st->pwm, &wf, false);
102	if (ret < 0)
103		dev_err(st->dev, "failed to disable PWM: %d\n", ret);
104}
105
106static const struct spi_offload_trigger_ops spi_offload_trigger_pwm_ops = {
107	.match = spi_offload_trigger_pwm_match,
108	.validate = spi_offload_trigger_pwm_validate,
109	.enable = spi_offload_trigger_pwm_enable,
110	.disable = spi_offload_trigger_pwm_disable,
111};
112
113static void spi_offload_trigger_pwm_release(void *data)
114{
115	pwm_disable(data);
116}
117
118static int spi_offload_trigger_pwm_probe(struct platform_device *pdev)
119{
120	struct device *dev = &pdev->dev;
121	struct spi_offload_trigger_info info = {
122		.fwnode = dev_fwnode(dev),
123		.ops = &spi_offload_trigger_pwm_ops,
124	};
125	struct spi_offload_trigger_pwm_state *st;
126	struct pwm_state state;
127	int ret;
128
129	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
130	if (!st)
131		return -ENOMEM;
132
133	info.priv = st;
134	st->dev = dev;
135
136	st->pwm = devm_pwm_get(dev, NULL);
137	if (IS_ERR(st->pwm))
138		return dev_err_probe(dev, PTR_ERR(st->pwm), "failed to get PWM\n");
139
140	/* init with duty_cycle = 0, output enabled to ensure trigger off */
141	pwm_init_state(st->pwm, &state);
142	state.enabled = true;
143
144	ret = pwm_apply_might_sleep(st->pwm, &state);
145	if (ret < 0)
146		return dev_err_probe(dev, ret, "failed to apply PWM state\n");
147
148	ret = devm_add_action_or_reset(dev, spi_offload_trigger_pwm_release, st->pwm);
149	if (ret)
150		return ret;
151
152	return devm_spi_offload_trigger_register(dev, &info);
153}
154
155static const struct of_device_id spi_offload_trigger_pwm_of_match_table[] = {
156	{ .compatible = "pwm-trigger" },
157	{ }
158};
159MODULE_DEVICE_TABLE(of, spi_offload_trigger_pwm_of_match_table);
160
161static struct platform_driver spi_offload_trigger_pwm_driver = {
162	.driver = {
163		.name = "pwm-trigger",
164		.of_match_table = spi_offload_trigger_pwm_of_match_table,
165	},
166	.probe = spi_offload_trigger_pwm_probe,
167};
168module_platform_driver(spi_offload_trigger_pwm_driver);
169
170MODULE_AUTHOR("David Lechner <dlechner@baylibre.com>");
171MODULE_DESCRIPTION("Generic PWM trigger");
172MODULE_LICENSE("GPL");