From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff LaBundy Subject: [PATCH v4 4/7] pwm: Add support for Azoteq IQS620A PWM generator Date: Fri, 17 Jan 2020 02:35:57 +0000 Message-ID: <1579228475-6681-5-git-send-email-jeff@labundy.com> References: <1579228475-6681-1-git-send-email-jeff@labundy.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <1579228475-6681-1-git-send-email-jeff@labundy.com> Content-Language: en-US Sender: linux-input-owner@vger.kernel.org To: "lee.jones@linaro.org" , "dmitry.torokhov@gmail.com" , "thierry.reding@gmail.com" , "jic23@kernel.org" , "devicetree@vger.kernel.org" Cc: "linux-input@vger.kernel.org" , "u.kleine-koenig@pengutronix.de" , "linux-pwm@vger.kernel.org" , "knaack.h@gmx.de" , "lars@metafoo.de" , "pmeerw@pmeerw.net" , "linux-iio@vger.kernel.org" , "robh+dt@kernel.org" , "mark.rutland@arm.com" , Jeff LaBundy List-Id: linux-pwm@vger.kernel.org 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 --- Changes in v4: - Updated iqs620_pwm_apply and iqs620_pwm_get_state to hold the lock arou= nd only the minimum necessary code - Removed the completion protecting against early use of chip->pwms[0] fr= om inside iqs620_pwm_notifier in favor of cached register values - Updated iqs620_pwm_get_state to use the cached register values instead = of reading IQS620_PWR_SETTINGS_PWM_OUT and IQS620_PWM_DUTY_CYCLE (both equ= al to zero by default) - Added a comment in iqs620_pwm_notifier to note that the parent MFD driv= er prints an error message in the event of a device reset Changes in v3: - Updated the commit message to say "~0.4%" instead of "0.4%" - Clarified the effect of duty cycle and state changes in the 'Limitation= s' section and added a restriction regarding 0% duty cycle - Added a comment in iqs620_pwm_apply to explain how duty cycle is derive= d - Updated iqs620_pwm_apply to disable the output first and enable it last= to prevent temporarily driving a stale duty cycle - Rounded the calculation for duty cycle up and down in iqs620_pwm_get_st= ate and iqs620_pwm_apply, respectively - Added a comment in iqs620_pwm_get_state to explain what it reports foll= ow- ing requests to set duty cycle to 0% - Added a lock to prevent back-to-back access of IQS620_PWR_SETTINGS_PWM_= OUT and IQS620_PWM_DUTY_CYCLE from being interrupted - Updated iqs620_pwm_notifier to reference pwm->state directly as opposed= to calling pwm_get_state - Moved notifier unregistration back to a device-managed action - Added a completion to prevent iqs620_pwm_notifier from referencing the pwm_chip structure until it has been initialized by pwmchip_add Changes in v2: - Merged 'Copyright' and 'Author' lines into one in introductory comments - Added 'Limitations' section to introductory comments - Replaced 'error' with 'ret' throughout - Added const qualifier to state argument of iqs620_pwm_apply and removed= all modifications to the variable's contents - Updated iqs620_pwm_apply to return -ENOTSUPP or -EINVAL if the requeste= d polarity is inverted or the requested period is below 1 ms, respectivel= y - Updated iqs620_pwm_apply to disable the PWM output if duty cycle is zer= o - Added iqs620_pwm_get_state - Eliminated tabbed alignment of pwm_ops and platform_driver struct membe= rs - Moved notifier unregistration to already present iqs620_pwm_remove, whi= ch eliminated the need for a device-managed action and ready flag - Added a comment in iqs620_pwm_probe to explain the order of operations - Changed Kconfig "depends on" logic to MFD_IQS62X || COMPILE_TEST drivers/pwm/Kconfig | 10 ++ drivers/pwm/Makefile | 1 + drivers/pwm/pwm-iqs620a.c | 258 ++++++++++++++++++++++++++++++++++++++++++= ++++ 3 files changed, 269 insertions(+) create mode 100644 drivers/pwm/pwm-iqs620a.c diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index bd21655..60bcf6c 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -222,6 +222,16 @@ config PWM_IMX_TPM To compile this driver as a module, choose M here: the module will be called pwm-imx-tpm. +config PWM_IQS620A + tristate "Azoteq IQS620A PWM support" + depends on MFD_IQS62X || COMPILE_TEST + help + Generic PWM framework driver for the Azoteq IQS620A multi-function + sensor. + + To compile this driver as a module, choose M here: the module will + be called pwm-iqs620a. + config PWM_JZ4740 tristate "Ingenic JZ47xx PWM support" depends on MACH_INGENIC diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 9a47507..a59c710 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG) +=3D pwm-img.o obj-$(CONFIG_PWM_IMX1) +=3D pwm-imx1.o obj-$(CONFIG_PWM_IMX27) +=3D pwm-imx27.o obj-$(CONFIG_PWM_IMX_TPM) +=3D pwm-imx-tpm.o +obj-$(CONFIG_PWM_IQS620A) +=3D pwm-iqs620a.o obj-$(CONFIG_PWM_JZ4740) +=3D pwm-jz4740.o obj-$(CONFIG_PWM_LP3943) +=3D pwm-lp3943.o obj-$(CONFIG_PWM_LPC18XX_SCT) +=3D pwm-lpc18xx-sct.o diff --git a/drivers/pwm/pwm-iqs620a.c b/drivers/pwm/pwm-iqs620a.c new file mode 100644 index 0000000..75ca482 --- /dev/null +++ b/drivers/pwm/pwm-iqs620a.c @@ -0,0 +1,258 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Azoteq IQS620A PWM Generator + * + * Copyright (C) 2019 Jeff LaBundy + * + * Limitations: + * - The period is fixed to 1 ms and is generated continuously despite cha= nges + * to the duty cycle or enable/disable state. + * - Changes to the duty cycle or enable/disable state take effect immedia= tely + * and may result in a glitch during the period in which the change is m= ade. + * - 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 resi= stor + * to hold the GPIO3/LTX pin low. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 !=3D PWM_POLARITY_NORMAL) + return -ENOTSUPP; + + if (state->period < IQS620_PWM_PERIOD_NS) + return -EINVAL; + + iqs620_pwm =3D container_of(chip, struct iqs620_pwm_private, chip); + iqs62x =3D iqs620_pwm->iqs62x; + + /* + * The duty cycle generated by the device is calculated as follows: + * + * duty_cycle =3D (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 on-board pull-down resistor to hold the GPIO3/LTX pin low. + */ + duty_scale =3D state->duty_cycle * 256 / IQS620_PWM_PERIOD_NS; + + mutex_lock(&iqs620_pwm->lock); + + if (!state->enabled || !duty_scale) { + ret =3D regmap_update_bits(iqs62x->map, IQS620_PWR_SETTINGS, + IQS620_PWR_SETTINGS_PWM_OUT, 0); + if (ret) + goto err_mutex; + } + + if (duty_scale) { + u8 duty_val =3D min(duty_scale - 1, 0xFF); + + ret =3D regmap_write(iqs62x->map, IQS620_PWM_DUTY_CYCLE, + duty_val); + if (ret) + goto err_mutex; + + iqs620_pwm->duty_val =3D duty_val; + } + + if (state->enabled && duty_scale) { + ret =3D regmap_update_bits(iqs62x->map, IQS620_PWR_SETTINGS, + IQS620_PWR_SETTINGS_PWM_OUT, 0xFF); + if (ret) + goto err_mutex; + } + + iqs620_pwm->out_en =3D 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 =3D 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 =3D iqs620_pwm->out_en; + state->duty_cycle =3D DIV_ROUND_UP((iqs620_pwm->duty_val + 1) * + IQS620_PWM_PERIOD_NS, 256); + + mutex_unlock(&iqs620_pwm->lock); + + state->period =3D 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 =3D container_of(notifier, struct iqs620_pwm_private, + notifier); + iqs62x =3D 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 =3D regmap_write(iqs62x->map, IQS620_PWM_DUTY_CYCLE, + iqs620_pwm->duty_val); + if (ret) + goto err_mutex; + + ret =3D regmap_update_bits(iqs62x->map, 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 =3D { + .apply =3D iqs620_pwm_apply, + .get_state =3D iqs620_pwm_get_state, + .owner =3D THIS_MODULE, +}; + +static void iqs620_pwm_notifier_unregister(void *context) +{ + struct iqs620_pwm_private *iqs620_pwm =3D context; + int ret; + + ret =3D 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 iqs620_pwm_private *iqs620_pwm; + int ret; + + iqs620_pwm =3D devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); + if (!iqs620_pwm) + return -ENOMEM; + + platform_set_drvdata(pdev, iqs620_pwm); + iqs620_pwm->iqs62x =3D dev_get_drvdata(pdev->dev.parent); + + iqs620_pwm->chip.dev =3D &pdev->dev; + iqs620_pwm->chip.ops =3D &iqs620_pwm_ops; + iqs620_pwm->chip.base =3D -1; + iqs620_pwm->chip.npwm =3D 1; + + mutex_init(&iqs620_pwm->lock); + + iqs620_pwm->notifier.notifier_call =3D iqs620_pwm_notifier; + ret =3D 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 =3D devm_add_action_or_reset(&pdev->dev, + iqs620_pwm_notifier_unregister, + iqs620_pwm); + if (ret) + return ret; + + ret =3D 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 =3D platform_get_drvdata(pdev); + int ret; + + ret =3D 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 =3D { + .driver =3D { + .name =3D IQS620_DRV_NAME_PWM, + }, + .probe =3D iqs620_pwm_probe, + .remove =3D iqs620_pwm_remove, +}; +module_platform_driver(iqs620_pwm_platform_driver); + +MODULE_AUTHOR("Jeff LaBundy "); +MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:" IQS620_DRV_NAME_PWM); -- 2.7.4