diff options
author | Jeff LaBundy <jeff@labundy.com> | 2020-04-12 21:15:16 -0500 |
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committer | Thierry Reding <thierry.reding@gmail.com> | 2020-04-14 16:02:28 +0200 |
commit | 6f0841a8197b20d01de9d41cb1eeed09b7b31f9b (patch) | |
tree | 8240cf830156551dc1a9c7ab57fff1ab2a19c00a /drivers/pwm/pwm-iqs620a.c | |
parent | 07b053ff1c6ee7c972e7e3d0915d05f1b1280f14 (diff) | |
download | linux-6f0841a8197b20d01de9d41cb1eeed09b7b31f9b.tar.bz2 |
pwm: Add support for Azoteq IQS620A PWM generator
This patch adds support for the Azoteq IQS620A, capable of generating
a 1-kHz PWM output with duty cycle between ~0.4% and 100% (inclusive).
Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm/pwm-iqs620a.c')
-rw-r--r-- | drivers/pwm/pwm-iqs620a.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-iqs620a.c b/drivers/pwm/pwm-iqs620a.c new file mode 100644 index 000000000000..674f0e238ba0 --- /dev/null +++ b/drivers/pwm/pwm-iqs620a.c @@ -0,0 +1,270 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Azoteq IQS620A PWM Generator + * + * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com> + * + * Limitations: + * - The period is fixed to 1 ms and is generated continuously despite changes + * to the duty cycle or enable/disable state. + * - Changes to the duty cycle or enable/disable state take effect immediately + * and may result in a glitch during the period in which the change is made. + * - The device cannot generate a 0% duty cycle. For duty cycles below 1 / 256 + * ms, the output is disabled and relies upon an external pull-down resistor + * to hold the GPIO3/LTX pin low. + */ + +#include <linux/device.h> +#include <linux/kernel.h> +#include <linux/mfd/iqs62x.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/notifier.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/regmap.h> +#include <linux/slab.h> + +#define IQS620_PWR_SETTINGS 0xD2 +#define IQS620_PWR_SETTINGS_PWM_OUT BIT(7) + +#define IQS620_PWM_DUTY_CYCLE 0xD8 + +#define IQS620_PWM_PERIOD_NS 1000000 + +struct iqs620_pwm_private { + struct iqs62x_core *iqs62x; + struct pwm_chip chip; + struct notifier_block notifier; + struct mutex lock; + bool out_en; + u8 duty_val; +}; + +static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct iqs620_pwm_private *iqs620_pwm; + struct iqs62x_core *iqs62x; + int duty_scale, ret; + + if (state->polarity != PWM_POLARITY_NORMAL) + return -ENOTSUPP; + + if (state->period < IQS620_PWM_PERIOD_NS) + return -EINVAL; + + iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); + iqs62x = iqs620_pwm->iqs62x; + + /* + * The duty cycle generated by the device is calculated as follows: + * + * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms + * + * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255 + * (inclusive). Therefore the lowest duty cycle the device can generate + * while the output is enabled is 1 / 256 ms. + * + * For lower duty cycles (e.g. 0), the PWM output is simply disabled to + * allow an external pull-down resistor to hold the GPIO3/LTX pin low. + */ + duty_scale = state->duty_cycle * 256 / IQS620_PWM_PERIOD_NS; + + mutex_lock(&iqs620_pwm->lock); + + if (!state->enabled || !duty_scale) { + ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, + IQS620_PWR_SETTINGS_PWM_OUT, 0); + if (ret) + goto err_mutex; + } + + if (duty_scale) { + u8 duty_val = min(duty_scale - 1, 0xFF); + + ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, + duty_val); + if (ret) + goto err_mutex; + + iqs620_pwm->duty_val = duty_val; + } + + if (state->enabled && duty_scale) { + ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, + IQS620_PWR_SETTINGS_PWM_OUT, 0xFF); + if (ret) + goto err_mutex; + } + + iqs620_pwm->out_en = state->enabled; + +err_mutex: + mutex_unlock(&iqs620_pwm->lock); + + return ret; +} + +static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct iqs620_pwm_private *iqs620_pwm; + + iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); + + mutex_lock(&iqs620_pwm->lock); + + /* + * Since the device cannot generate a 0% duty cycle, requests to do so + * cause subsequent calls to iqs620_pwm_get_state to report the output + * as disabled with duty cycle equal to that which was in use prior to + * the request. This is not ideal, but is the best compromise based on + * the capabilities of the device. + */ + state->enabled = iqs620_pwm->out_en; + state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) * + IQS620_PWM_PERIOD_NS, 256); + + mutex_unlock(&iqs620_pwm->lock); + + state->period = IQS620_PWM_PERIOD_NS; +} + +static int iqs620_pwm_notifier(struct notifier_block *notifier, + unsigned long event_flags, void *context) +{ + struct iqs620_pwm_private *iqs620_pwm; + struct iqs62x_core *iqs62x; + int ret; + + if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) + return NOTIFY_DONE; + + iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, + notifier); + iqs62x = iqs620_pwm->iqs62x; + + mutex_lock(&iqs620_pwm->lock); + + /* + * The parent MFD driver already prints an error message in the event + * of a device reset, so nothing else is printed here unless there is + * an additional failure. + */ + ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, + iqs620_pwm->duty_val); + if (ret) + goto err_mutex; + + ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, + IQS620_PWR_SETTINGS_PWM_OUT, + iqs620_pwm->out_en ? 0xFF : 0); + +err_mutex: + mutex_unlock(&iqs620_pwm->lock); + + if (ret) { + dev_err(iqs620_pwm->chip.dev, + "Failed to re-initialize device: %d\n", ret); + return NOTIFY_BAD; + } + + return NOTIFY_OK; +} + +static const struct pwm_ops iqs620_pwm_ops = { + .apply = iqs620_pwm_apply, + .get_state = iqs620_pwm_get_state, + .owner = THIS_MODULE, +}; + +static void iqs620_pwm_notifier_unregister(void *context) +{ + struct iqs620_pwm_private *iqs620_pwm = context; + int ret; + + ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, + &iqs620_pwm->notifier); + if (ret) + dev_err(iqs620_pwm->chip.dev, + "Failed to unregister notifier: %d\n", ret); +} + +static int iqs620_pwm_probe(struct platform_device *pdev) +{ + struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent); + struct iqs620_pwm_private *iqs620_pwm; + unsigned int val; + int ret; + + iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); + if (!iqs620_pwm) + return -ENOMEM; + + platform_set_drvdata(pdev, iqs620_pwm); + iqs620_pwm->iqs62x = iqs62x; + + ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val); + if (ret) + return ret; + iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT; + + ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val); + if (ret) + return ret; + iqs620_pwm->duty_val = val; + + iqs620_pwm->chip.dev = &pdev->dev; + iqs620_pwm->chip.ops = &iqs620_pwm_ops; + iqs620_pwm->chip.base = -1; + iqs620_pwm->chip.npwm = 1; + + mutex_init(&iqs620_pwm->lock); + + iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; + ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, + &iqs620_pwm->notifier); + if (ret) { + dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret); + return ret; + } + + ret = devm_add_action_or_reset(&pdev->dev, + iqs620_pwm_notifier_unregister, + iqs620_pwm); + if (ret) + return ret; + + ret = pwmchip_add(&iqs620_pwm->chip); + if (ret) + dev_err(&pdev->dev, "Failed to add device: %d\n", ret); + + return ret; +} + +static int iqs620_pwm_remove(struct platform_device *pdev) +{ + struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev); + int ret; + + ret = pwmchip_remove(&iqs620_pwm->chip); + if (ret) + dev_err(&pdev->dev, "Failed to remove device: %d\n", ret); + + return ret; +} + +static struct platform_driver iqs620_pwm_platform_driver = { + .driver = { + .name = "iqs620a-pwm", + }, + .probe = iqs620_pwm_probe, + .remove = iqs620_pwm_remove, +}; +module_platform_driver(iqs620_pwm_platform_driver); + +MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>"); +MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:iqs620a-pwm"); |