[PATCH 05/10] iio: trigger: at91-rtc-trigger: introduce at91 rtc adc trigger driver

[<Eugen.Hristev@microchip.com>]

From: Eugen Hristev <eugen.hristev@microchip.com>

The AT91 RTC ADC trigger driver registers a trigger into the iio subsystem,
which can be associated with at91_sama5d2-adc compatible drivers.
The SAMA5D2 SoC contains a hardware link between the RTC block and the ADC
block that will allow the RTC to trigger the ADC to perform conversions.
The at91-rtc-trigger will allow the customisation of the trigger frequency
from sysfs:
trigger_frequency_hz_available will display possible frequencies in Hz
trigger_frequency_hz will allow configuring this frequency.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
 drivers/iio/trigger/Kconfig            |  10 ++
 drivers/iio/trigger/Makefile           |   1 +
 drivers/iio/trigger/at91-rtc-trigger.c | 213 +++++++++++++++++++++++++++++++++
 3 files changed, 224 insertions(+)
 create mode 100644 drivers/iio/trigger/at91-rtc-trigger.c

diff --git a/drivers/iio/trigger/Kconfig b/drivers/iio/trigger/Kconfig
index 8cef2f7..dc7e6f4 100644
--- a/drivers/iio/trigger/Kconfig
+++ b/drivers/iio/trigger/Kconfig
@@ -68,4 +68,14 @@ config IIO_SYSFS_TRIGGER
 	  To compile this driver as a module, choose M here: the
 	  module will be called iio-trig-sysfs.
 
+config IIO_AT91_RTC_TRIGGER
+	tristate "AT91 RTC trigger"
+	help
+	  Provides support for using AT91 RTC IP block to generate trigger
+	  events for ADC devices.
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called at91-rtc-trigger.
+
 endmenu
diff --git a/drivers/iio/trigger/Makefile b/drivers/iio/trigger/Makefile
index f3d11ac..6512436 100644
--- a/drivers/iio/trigger/Makefile
+++ b/drivers/iio/trigger/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_IIO_STM32_LPTIMER_TRIGGER) += stm32-lptimer-trigger.o
 obj-$(CONFIG_IIO_STM32_TIMER_TRIGGER) += stm32-timer-trigger.o
 obj-$(CONFIG_IIO_SYSFS_TRIGGER) += iio-trig-sysfs.o
 obj-$(CONFIG_IIO_TIGHTLOOP_TRIGGER) += iio-trig-loop.o
+obj-$(CONFIG_IIO_AT91_RTC_TRIGGER) += at91-rtc-trigger.o
diff --git a/drivers/iio/trigger/at91-rtc-trigger.c b/drivers/iio/trigger/at91-rtc-trigger.c
new file mode 100644
index 0000000..8cdcfeb
--- /dev/null
+++ b/drivers/iio/trigger/at91-rtc-trigger.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2019 Microchip Technology, Inc. and its subsidiaries
+ *
+ * Author: Eugen Hristev <eugen.hristev@microchip.com>
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/irq_work.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger.h>
+
+#define at91_adc_readl(t, reg)		readl_relaxed((t)->base + (reg))
+#define at91_adc_writel(t, reg, val)	writel_relaxed(val, (t)->base + (reg))
+
+#define AT91_RTC_MR		0x4
+#define AT91_RTC_OUT0_MASK	GENMASK(18, 16)
+#define AT91_RTC_OUT0_NO_WAVE	(0x0 << 16)
+#define AT91_RTC_OUT0_1HZ	(0x1 << 16)
+#define AT91_RTC_OUT0_32HZ	(0x2 << 16)
+#define AT91_RTC_OUT0_64HZ	(0x3 << 16)
+#define AT91_RTC_OUT0_512HZ	(0x4 << 16)
+
+/* attribute pack list */
+#define AT91_RTC_1HZ		1
+#define AT91_RTC_32HZ		32
+#define AT91_RTC_64HZ		64
+#define AT91_RTC_512HZ		512
+
+struct at91_rtc_adc_trig {
+	struct iio_trigger	*trig;
+	void __iomem		*base;
+	unsigned int		hz_config;
+};
+
+static int at91_hz_config_sysfs_to_reg(unsigned int hz_config)
+{
+	switch (hz_config) {
+	case AT91_RTC_1HZ:
+		return AT91_RTC_OUT0_1HZ;
+	case AT91_RTC_32HZ:
+		return AT91_RTC_OUT0_32HZ;
+	case AT91_RTC_64HZ:
+		return AT91_RTC_OUT0_64HZ;
+	case AT91_RTC_512HZ:
+		return AT91_RTC_OUT0_512HZ;
+	}
+	return AT91_RTC_OUT0_1HZ;
+}
+
+static int at91_configure_trigger(struct iio_trigger *trig, bool state)
+{
+	struct at91_rtc_adc_trig *t = iio_trigger_get_drvdata(trig);
+	u32 mr = at91_adc_readl(t, AT91_RTC_MR);
+
+	mr &= ~AT91_RTC_OUT0_MASK;
+
+	if (state)
+		mr |= at91_hz_config_sysfs_to_reg(t->hz_config);
+
+	at91_adc_writel(t, AT91_RTC_MR, mr);
+
+	return 0;
+}
+
+static const struct iio_trigger_ops at91_rtc_adc_trigger_ops = {
+	.set_trigger_state = &at91_configure_trigger,
+};
+
+static ssize_t at91_rtc_trigger_frequency_get(struct device *dev,
+					      struct device_attribute *attr,
+					      char *buf)
+{
+	struct iio_trigger *trig = to_iio_trigger(dev);
+	struct at91_rtc_adc_trig *t = iio_trigger_get_drvdata(trig);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", t->hz_config);
+}
+
+static ssize_t at91_rtc_trigger_frequency_set(struct device *dev,
+					      struct device_attribute *attr,
+					      const char *buf, size_t count)
+{
+	struct iio_trigger *trig = to_iio_trigger(dev);
+	struct at91_rtc_adc_trig *t = iio_trigger_get_drvdata(trig);
+	int ret;
+	unsigned int val;
+
+	ret = kstrtou32(buf, 10, &val);
+
+	if (ret)
+		return ret;
+
+	if (val != AT91_RTC_1HZ && val != AT91_RTC_32HZ &&
+	    val != AT91_RTC_64HZ && val != AT91_RTC_512HZ)
+		return -EINVAL;
+
+	t->hz_config = val;
+
+	return count;
+}
+
+static IIO_DEVICE_ATTR(trigger_frequency_hz, 0644,
+		       at91_rtc_trigger_frequency_get,
+		       at91_rtc_trigger_frequency_set, 0);
+
+static IIO_CONST_ATTR(trigger_frequency_hz_available,
+		      __stringify(AT91_RTC_1HZ) " "
+		      __stringify(AT91_RTC_32HZ) " "
+		      __stringify(AT91_RTC_64HZ) " "
+		      __stringify(AT91_RTC_512HZ));
+
+static struct attribute *at91_rtc_adc_trigger_attributes[] = {
+	&iio_const_attr_trigger_frequency_hz_available.dev_attr.attr,
+	&iio_dev_attr_trigger_frequency_hz.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group at91_rtc_adc_trigger_attribute_group = {
+	.attrs = at91_rtc_adc_trigger_attributes,
+};
+
+static const struct attribute_group *at91_rtc_adc_trigger_attr_groups[] = {
+	&at91_rtc_adc_trigger_attribute_group,
+	NULL
+};
+
+static void at91_rtc_adc_trigger_remove(void *priv)
+{
+	struct at91_rtc_adc_trig *t = priv;
+
+	iio_trigger_unregister(t->trig);
+	iio_trigger_free(t->trig);
+}
+
+static int at91_rtc_adc_trigger_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct resource	*res;
+	struct at91_rtc_adc_trig *t;
+	int ret = 0;
+
+	t = devm_kzalloc(dev, sizeof(*t), GFP_KERNEL);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
+	t->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(t->base))
+		return PTR_ERR(t->base);
+
+	t->trig = iio_trigger_alloc("%x.at91_rtc_adc", res->start);
+	if (!t->trig) {
+		ret = -ENOMEM;
+		return ret;
+	}
+
+	t->hz_config = AT91_RTC_1HZ;
+
+	t->trig->ops = &at91_rtc_adc_trigger_ops;
+	t->trig->dev.parent = dev;
+	t->trig->dev.groups = at91_rtc_adc_trigger_attr_groups;
+
+	iio_trigger_set_drvdata(t->trig, t);
+
+	ret = iio_trigger_register(t->trig);
+	if (ret) {
+		dev_err(dev, "failed to register trigger.\n");
+		goto at91_rtc_adc_trigger_probe_fail_register;
+	}
+
+	ret = devm_add_action_or_reset(dev, at91_rtc_adc_trigger_remove, t);
+	if (ret) {
+		dev_err(dev, "failed to add disable action.\n");
+		goto at91_rtc_adc_trigger_probe_fail_add_action;
+	}
+
+	return 0;
+
+at91_rtc_adc_trigger_probe_fail_add_action:
+	iio_trigger_unregister(t->trig);
+at91_rtc_adc_trigger_probe_fail_register:
+	iio_trigger_free(t->trig);
+	return ret;
+}
+
+static const struct of_device_id at91_rtc_adc_trigger_of_match[] = {
+	{
+		.compatible = "microchip,rtc-adc-trigger",
+	},
+	{ /* end node */ },
+};
+MODULE_DEVICE_TABLE(of, at91_rtc_adc_trigger_of_match);
+
+static struct platform_driver at91_rtc_adc_trigger_driver = {
+	.probe = at91_rtc_adc_trigger_probe,
+	.driver = {
+		.name = "at91-rtc-adc-trigger",
+		.of_match_table = at91_rtc_adc_trigger_of_match,
+	},
+};
+module_platform_driver(at91_rtc_adc_trigger_driver);
+
+MODULE_AUTHOR("Eugen Hristev <eugen.hristev@microchip.com>");
+MODULE_DESCRIPTION("AT91 RTC ADC trigger driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:iio-at91-rtc-trigger");
-- 
2.7.4