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244 lines
6.4 KiB
244 lines
6.4 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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/* |
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* Azoteq IQS620A PWM Generator |
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* |
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* Copyright (C) 2019 Jeff LaBundy <[email protected]> |
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* |
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* Limitations: |
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* - The period is fixed to 1 ms and is generated continuously despite changes |
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* to the duty cycle or enable/disable state. |
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* - Changes to the duty cycle or enable/disable state take effect immediately |
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* and may result in a glitch during the period in which the change is made. |
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* - The device cannot generate a 0% duty cycle. For duty cycles below 1 / 256 |
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* ms, the output is disabled and relies upon an external pull-down resistor |
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* to hold the GPIO3/LTX pin low. |
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*/ |
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#include <linux/device.h> |
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#include <linux/kernel.h> |
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#include <linux/mfd/iqs62x.h> |
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#include <linux/module.h> |
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#include <linux/mutex.h> |
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#include <linux/notifier.h> |
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#include <linux/platform_device.h> |
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#include <linux/pwm.h> |
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#include <linux/regmap.h> |
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#include <linux/slab.h> |
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#define IQS620_PWR_SETTINGS 0xd2 |
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#define IQS620_PWR_SETTINGS_PWM_OUT BIT(7) |
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#define IQS620_PWM_DUTY_CYCLE 0xd8 |
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#define IQS620_PWM_PERIOD_NS 1000000 |
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struct iqs620_pwm_private { |
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struct iqs62x_core *iqs62x; |
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struct pwm_chip chip; |
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struct notifier_block notifier; |
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struct mutex lock; |
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unsigned int duty_scale; |
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}; |
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static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm, |
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unsigned int duty_scale) |
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{ |
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struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x; |
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int ret; |
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if (!duty_scale) |
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return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, |
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IQS620_PWR_SETTINGS_PWM_OUT, 0); |
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ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, |
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duty_scale - 1); |
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if (ret) |
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return ret; |
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return regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, |
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IQS620_PWR_SETTINGS_PWM_OUT, 0xff); |
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} |
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static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, |
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const struct pwm_state *state) |
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{ |
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struct iqs620_pwm_private *iqs620_pwm; |
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unsigned int duty_cycle; |
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unsigned int duty_scale; |
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int ret; |
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if (state->polarity != PWM_POLARITY_NORMAL) |
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return -EINVAL; |
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if (state->period < IQS620_PWM_PERIOD_NS) |
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return -EINVAL; |
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iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); |
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/* |
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* The duty cycle generated by the device is calculated as follows: |
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* |
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* duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms |
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* |
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* ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255 |
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* (inclusive). Therefore the lowest duty cycle the device can generate |
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* while the output is enabled is 1 / 256 ms. |
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* |
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* For lower duty cycles (e.g. 0), the PWM output is simply disabled to |
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* allow an external pull-down resistor to hold the GPIO3/LTX pin low. |
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*/ |
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duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS); |
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duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS; |
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if (!state->enabled) |
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duty_scale = 0; |
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mutex_lock(&iqs620_pwm->lock); |
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ret = iqs620_pwm_init(iqs620_pwm, duty_scale); |
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if (!ret) |
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iqs620_pwm->duty_scale = duty_scale; |
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mutex_unlock(&iqs620_pwm->lock); |
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return ret; |
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} |
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static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, |
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struct pwm_state *state) |
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{ |
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struct iqs620_pwm_private *iqs620_pwm; |
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iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); |
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mutex_lock(&iqs620_pwm->lock); |
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/* |
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* Since the device cannot generate a 0% duty cycle, requests to do so |
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* cause subsequent calls to iqs620_pwm_get_state to report the output |
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* as disabled. This is not ideal, but is the best compromise based on |
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* the capabilities of the device. |
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*/ |
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state->enabled = iqs620_pwm->duty_scale > 0; |
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state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale * |
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IQS620_PWM_PERIOD_NS, 256); |
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mutex_unlock(&iqs620_pwm->lock); |
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state->period = IQS620_PWM_PERIOD_NS; |
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} |
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static int iqs620_pwm_notifier(struct notifier_block *notifier, |
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unsigned long event_flags, void *context) |
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{ |
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struct iqs620_pwm_private *iqs620_pwm; |
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int ret; |
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if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) |
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return NOTIFY_DONE; |
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iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, |
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notifier); |
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mutex_lock(&iqs620_pwm->lock); |
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/* |
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* The parent MFD driver already prints an error message in the event |
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* of a device reset, so nothing else is printed here unless there is |
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* an additional failure. |
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*/ |
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ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale); |
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mutex_unlock(&iqs620_pwm->lock); |
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if (ret) { |
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dev_err(iqs620_pwm->chip.dev, |
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"Failed to re-initialize device: %d\n", ret); |
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return NOTIFY_BAD; |
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} |
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return NOTIFY_OK; |
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} |
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static const struct pwm_ops iqs620_pwm_ops = { |
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.apply = iqs620_pwm_apply, |
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.get_state = iqs620_pwm_get_state, |
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.owner = THIS_MODULE, |
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}; |
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static void iqs620_pwm_notifier_unregister(void *context) |
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{ |
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struct iqs620_pwm_private *iqs620_pwm = context; |
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int ret; |
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ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, |
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&iqs620_pwm->notifier); |
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if (ret) |
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dev_err(iqs620_pwm->chip.dev, |
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"Failed to unregister notifier: %d\n", ret); |
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} |
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static int iqs620_pwm_probe(struct platform_device *pdev) |
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{ |
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struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent); |
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struct iqs620_pwm_private *iqs620_pwm; |
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unsigned int val; |
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int ret; |
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iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); |
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if (!iqs620_pwm) |
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return -ENOMEM; |
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iqs620_pwm->iqs62x = iqs62x; |
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ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val); |
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if (ret) |
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return ret; |
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if (val & IQS620_PWR_SETTINGS_PWM_OUT) { |
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ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val); |
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if (ret) |
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return ret; |
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iqs620_pwm->duty_scale = val + 1; |
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} |
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iqs620_pwm->chip.dev = &pdev->dev; |
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iqs620_pwm->chip.ops = &iqs620_pwm_ops; |
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iqs620_pwm->chip.npwm = 1; |
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mutex_init(&iqs620_pwm->lock); |
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iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; |
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ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, |
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&iqs620_pwm->notifier); |
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if (ret) { |
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dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret); |
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return ret; |
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} |
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ret = devm_add_action_or_reset(&pdev->dev, |
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iqs620_pwm_notifier_unregister, |
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iqs620_pwm); |
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if (ret) |
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return ret; |
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ret = devm_pwmchip_add(&pdev->dev, &iqs620_pwm->chip); |
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if (ret) |
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dev_err(&pdev->dev, "Failed to add device: %d\n", ret); |
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return ret; |
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} |
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static struct platform_driver iqs620_pwm_platform_driver = { |
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.driver = { |
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.name = "iqs620a-pwm", |
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}, |
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.probe = iqs620_pwm_probe, |
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}; |
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module_platform_driver(iqs620_pwm_platform_driver); |
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MODULE_AUTHOR("Jeff LaBundy <[email protected]>"); |
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MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); |
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MODULE_LICENSE("GPL"); |
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MODULE_ALIAS("platform:iqs620a-pwm");
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