1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Azoteq IQS620A PWM Generator
  4 *
  5 * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com>
  6 *
  7 * Limitations:
  8 * - The period is fixed to 1 ms and is generated continuously despite changes
  9 *   to the duty cycle or enable/disable state.
 10 * - Changes to the duty cycle or enable/disable state take effect immediately
 11 *   and may result in a glitch during the period in which the change is made.
 12 * - The device cannot generate a 0% duty cycle. For duty cycles below 1 / 256
 13 *   ms, the output is disabled and relies upon an external pull-down resistor
 14 *   to hold the GPIO3/LTX pin low.
 15 */
 16
 17#include <linux/device.h>
 18#include <linux/kernel.h>
 19#include <linux/mfd/iqs62x.h>
 20#include <linux/module.h>
 21#include <linux/mutex.h>
 22#include <linux/notifier.h>
 23#include <linux/platform_device.h>
 24#include <linux/pwm.h>
 25#include <linux/regmap.h>
 26#include <linux/slab.h>
 27
 28#define IQS620_PWR_SETTINGS			0xd2
 29#define IQS620_PWR_SETTINGS_PWM_OUT		BIT(7)
 30
 31#define IQS620_PWM_DUTY_CYCLE			0xd8
 32
 33#define IQS620_PWM_PERIOD_NS			1000000
 34
 35struct iqs620_pwm_private {
 36	struct iqs62x_core *iqs62x;
 37	struct pwm_chip chip;
 38	struct notifier_block notifier;
 39	struct mutex lock;
 40	unsigned int duty_scale;
 41};
 42
 43static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm,
 44			   unsigned int duty_scale)
 45{
 46	struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x;
 47	int ret;
 48
 49	if (!duty_scale)
 50		return regmap_clear_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
 51					 IQS620_PWR_SETTINGS_PWM_OUT);
 52
 53	ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
 54			   duty_scale - 1);
 55	if (ret)
 56		return ret;
 57
 58	return regmap_set_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
 59			       IQS620_PWR_SETTINGS_PWM_OUT);
 60}
 61
 62static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 63			    const struct pwm_state *state)
 64{
 65	struct iqs620_pwm_private *iqs620_pwm;
 66	unsigned int duty_cycle;
 67	unsigned int duty_scale;
 68	int ret;
 69
 70	if (state->polarity != PWM_POLARITY_NORMAL)
 71		return -EINVAL;
 72
 73	if (state->period < IQS620_PWM_PERIOD_NS)
 74		return -EINVAL;
 75
 76	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
 77
 78	/*
 79	 * The duty cycle generated by the device is calculated as follows:
 80	 *
 81	 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
 82	 *
 83	 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255
 84	 * (inclusive). Therefore the lowest duty cycle the device can generate
 85	 * while the output is enabled is 1 / 256 ms.
 86	 *
 87	 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to
 88	 * allow an external pull-down resistor to hold the GPIO3/LTX pin low.
 89	 */
 90	duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
 91	duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
 92
 93	if (!state->enabled)
 94		duty_scale = 0;
 95
 96	mutex_lock(&iqs620_pwm->lock);
 97
 98	ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
 99	if (!ret)
100		iqs620_pwm->duty_scale = duty_scale;
101
102	mutex_unlock(&iqs620_pwm->lock);
103
104	return ret;
105}
106
107static int iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
108				struct pwm_state *state)
109{
110	struct iqs620_pwm_private *iqs620_pwm;
111
112	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
113
114	mutex_lock(&iqs620_pwm->lock);
115
116	/*
117	 * Since the device cannot generate a 0% duty cycle, requests to do so
118	 * cause subsequent calls to iqs620_pwm_get_state to report the output
119	 * as disabled. This is not ideal, but is the best compromise based on
120	 * the capabilities of the device.
121	 */
122	state->enabled = iqs620_pwm->duty_scale > 0;
123	state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale *
124					 IQS620_PWM_PERIOD_NS, 256);
125
126	mutex_unlock(&iqs620_pwm->lock);
127
128	state->period = IQS620_PWM_PERIOD_NS;
129	state->polarity = PWM_POLARITY_NORMAL;
130
131	return 0;
132}
133
134static int iqs620_pwm_notifier(struct notifier_block *notifier,
135			       unsigned long event_flags, void *context)
136{
137	struct iqs620_pwm_private *iqs620_pwm;
138	int ret;
139
140	if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
141		return NOTIFY_DONE;
142
143	iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
144				  notifier);
145
146	mutex_lock(&iqs620_pwm->lock);
147
148	/*
149	 * The parent MFD driver already prints an error message in the event
150	 * of a device reset, so nothing else is printed here unless there is
151	 * an additional failure.
152	 */
153	ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
154
155	mutex_unlock(&iqs620_pwm->lock);
156
157	if (ret) {
158		dev_err(iqs620_pwm->chip.dev,
159			"Failed to re-initialize device: %d\n", ret);
160		return NOTIFY_BAD;
161	}
162
163	return NOTIFY_OK;
164}
165
166static const struct pwm_ops iqs620_pwm_ops = {
167	.apply = iqs620_pwm_apply,
168	.get_state = iqs620_pwm_get_state,
169};
170
171static void iqs620_pwm_notifier_unregister(void *context)
172{
173	struct iqs620_pwm_private *iqs620_pwm = context;
174	int ret;
175
176	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
177						 &iqs620_pwm->notifier);
178	if (ret)
179		dev_err(iqs620_pwm->chip.dev,
180			"Failed to unregister notifier: %d\n", ret);
181}
182
183static int iqs620_pwm_probe(struct platform_device *pdev)
184{
185	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
186	struct iqs620_pwm_private *iqs620_pwm;
187	unsigned int val;
188	int ret;
189
190	iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
191	if (!iqs620_pwm)
192		return -ENOMEM;
193
194	iqs620_pwm->iqs62x = iqs62x;
195
196	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
197	if (ret)
198		return ret;
199
200	if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
201		ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
202		if (ret)
203			return ret;
204
205		iqs620_pwm->duty_scale = val + 1;
206	}
207
208	iqs620_pwm->chip.dev = &pdev->dev;
209	iqs620_pwm->chip.ops = &iqs620_pwm_ops;
210	iqs620_pwm->chip.npwm = 1;
211
212	mutex_init(&iqs620_pwm->lock);
213
214	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
215	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
216					       &iqs620_pwm->notifier);
217	if (ret) {
218		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
219		return ret;
220	}
221
222	ret = devm_add_action_or_reset(&pdev->dev,
223				       iqs620_pwm_notifier_unregister,
224				       iqs620_pwm);
225	if (ret)
226		return ret;
227
228	ret = devm_pwmchip_add(&pdev->dev, &iqs620_pwm->chip);
229	if (ret)
230		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
231
232	return ret;
233}
234
235static struct platform_driver iqs620_pwm_platform_driver = {
236	.driver = {
237		.name = "iqs620a-pwm",
238	},
239	.probe = iqs620_pwm_probe,
240};
241module_platform_driver(iqs620_pwm_platform_driver);
242
243MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
244MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
245MODULE_LICENSE("GPL");
246MODULE_ALIAS("platform:iqs620a-pwm");