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@xxxxxxxxxxx>
---
Changes in v4:
- Updated iqs620_pwm_apply and iqs620_pwm_get_state to hold the lock around
only the minimum necessary code
- Removed the completion protecting against early use of chip->pwms[0] from
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 equal
to zero by default)
- Added a comment in iqs620_pwm_notifier to note that the parent MFD driver
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 'Limitations'
section and added a restriction regarding 0% duty cycle
- Added a comment in iqs620_pwm_apply to explain how duty cycle is derived
- 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_state
and iqs620_pwm_apply, respectively
- Added a comment in iqs620_pwm_get_state to explain what it reports follow-
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 requested
polarity is inverted or the requested period is below 1 ms, respectively
- Updated iqs620_pwm_apply to disable the PWM output if duty cycle is zero
- Added iqs620_pwm_get_state
- Eliminated tabbed alignment of pwm_ops and platform_driver struct members
- Moved notifier unregistration to already present iqs620_pwm_remove, which
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-$(CONFIG_PWM_IMG) += pwm-img.o
obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o
obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o
obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o
+obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o
obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o
obj-$(CONFIG_PWM_LP3943) += pwm-lp3943.o
obj-$(CONFIG_PWM_LPC18XX_SCT) += 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 <jeff@xxxxxxxxxxx>
+ *
+ * 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 on-board 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->map, 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->map, 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->map, 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->map, IQS620_PWM_DUTY_CYCLE,
+ iqs620_pwm->duty_val);
+ if (ret)
+ goto err_mutex;
+
+ ret = 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 = {
+ .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 iqs620_pwm_private *iqs620_pwm;
+ 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 = dev_get_drvdata(pdev->dev.parent);
+
+ 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 = IQS620_DRV_NAME_PWM,
+ },
+ .probe = iqs620_pwm_probe,
+ .remove = iqs620_pwm_remove,
+};
+module_platform_driver(iqs620_pwm_platform_driver);
+
+MODULE_AUTHOR("Jeff LaBundy <jeff@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" IQS620_DRV_NAME_PWM);
--
2.7.4
