[PATCH v2 4/7] pwm: Add support for Azoteq IQS620A PWM generator

Jeff LaBundy
2019-12-09T00:38:48Z

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>
---
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 | 206 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 217 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..1ea11b9
--- /dev/null
+++ b/drivers/pwm/pwm-iqs620a.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Azoteq IQS620A PWM Generator
+ *
+ * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com>
+ *
+ * Limitations:
+ * - The period is not guaranteed to run to completion when the duty cycle is
+ * changed or the output is disabled.
+ * - The period is fixed to 1 ms.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/mfd/iqs62x.h>
+#include <linux/module.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;
+};
+
+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;
+ unsigned int pwm_out = 0;
+ 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;
+
+ duty_scale = DIV_ROUND_CLOSEST(state->duty_cycle * 256,
+ IQS620_PWM_PERIOD_NS);
+
+ if (duty_scale) {
+ ret = regmap_write(iqs62x->map, IQS620_PWM_DUTY_CYCLE,
+ min(duty_scale - 1, 0xFF));
+ if (ret)
+ return ret;
+
+ if (state->enabled)
+ pwm_out = IQS620_PWR_SETTINGS_PWM_OUT;
+ }
+
+ return regmap_update_bits(iqs62x->map, IQS620_PWR_SETTINGS,
+ IQS620_PWR_SETTINGS_PWM_OUT, pwm_out);
+}
+
+static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct iqs620_pwm_private *iqs620_pwm;
+ struct iqs62x_core *iqs62x;
+ unsigned int val;
+ int ret;
+
+ iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
+ iqs62x = iqs620_pwm->iqs62x;
+
+ ret = regmap_read(iqs62x->map, IQS620_PWR_SETTINGS, &val);
+ if (ret)
+ goto err_out;
+ state->enabled = val & IQS620_PWR_SETTINGS_PWM_OUT;
+
+ ret = regmap_read(iqs62x->map, IQS620_PWM_DUTY_CYCLE, &val);
+ if (ret)
+ goto err_out;
+ state->duty_cycle = DIV_ROUND_CLOSEST((val + 1) * IQS620_PWM_PERIOD_NS,
+ 256);
+ state->period = IQS620_PWM_PERIOD_NS;
+
+err_out:
+ if (ret)
+ dev_err(iqs620_pwm->chip.dev, "Failed to get state: %d\n", ret);
+}
+
+static int iqs620_pwm_notifier(struct notifier_block *notifier,
+ unsigned long event_flags, void *context)
+{
+ struct iqs620_pwm_private *iqs620_pwm;
+ struct pwm_state state;
+ int ret;
+
+ if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
+ return NOTIFY_DONE;
+
+ iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
+ notifier);
+ pwm_get_state(&iqs620_pwm->chip.pwms[0], &state);
+
+ ret = iqs620_pwm_apply(&iqs620_pwm->chip,
+ &iqs620_pwm->chip.pwms[0], &state);
+ 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 int iqs620_pwm_probe(struct platform_device *pdev)
+{
+ struct iqs620_pwm_private *iqs620_pwm;
+ int ret1, ret2;
+
+ 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;
+
+ ret1 = pwmchip_add(&iqs620_pwm->chip);
+ if (ret1) {
+ dev_err(&pdev->dev, "Failed to add device: %d\n", ret1);
+ return ret1;
+ }
+
+ /*
+ * Since iqs620_pwm_notifier uses iqs620_pwm->chip.pwms[], the notifier
+ * is not registered until pwmchip_add (which allocates that array) has
+ * been called. If registration fails, the newly added device has to be
+ * removed because the driver fails to probe and iqs620_pwm_remove will
+ * never be called.
+ */
+ iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
+ ret1 = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
+ &iqs620_pwm->notifier);
+ if (ret1) {
+ dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret1);
+
+ ret2 = pwmchip_remove(&iqs620_pwm->chip);
+ if (ret2) {
+ dev_err(&pdev->dev, "Failed to remove device: %d\n",
+ ret2);
+ return ret2;
+ }
+ }
+
+ return ret1;
+}
+
+static int iqs620_pwm_remove(struct platform_device *pdev)
+{
+ struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev);
+ int ret;
+
+ ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
+ &iqs620_pwm->notifier);
+ if (ret) {
+ dev_err(&pdev->dev, "Failed to unregister notifier: %d\n", ret);
+ return 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@labundy.com>");
+MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" IQS620_DRV_NAME_PWM);
--
2.7.4