hte: Add Tegra HTE test driver

The test driver uses IRQ and GPIO lines to timestamp using HTE
subsystem. The patch also adds compilation support in Kconfig and
Makefile.
Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/hte/Kconfig

@@ -23,4 +23,11 @@ config HTE_TEGRA194
 	  systems-on-chip. The driver supports 352 LIC IRQs and 39 AON GPIOs
 	  lines for timestamping in realtime.
 
+config HTE_TEGRA194_TEST
+        tristate "NVIDIA Tegra194 HTE Test"
+        depends on HTE_TEGRA194
+        help
+	  The NVIDIA Tegra194 GTE test driver demonstrates how to use HTE
+	  framework to timestamp GPIO and LIC IRQ lines.
+
 endif

drivers/hte/Makefile

 obj-$(CONFIG_HTE)		+= hte.o
 obj-$(CONFIG_HTE_TEGRA194)	+= hte-tegra194.o
-
+obj-$(CONFIG_HTE_TEGRA194_TEST) += hte-tegra194-test.o

drivers/hte/hte-tegra194-test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021-2022 NVIDIA Corporation
+ *
+ * Author: Dipen Patel <dipenp@nvidia.com>
+ */
+
+#include <linux/version.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/interrupt.h>
+#include <linux/gpio.h>
+#include <linux/timer.h>
+#include <linux/platform_device.h>
+#include <linux/workqueue.h>
+#include <linux/hte.h>
+
+/*
+ * This sample HTE GPIO test driver demonstrates HTE API usage by enabling
+ * hardware timestamp on gpio_in and specified LIC IRQ lines.
+ *
+ * Note: gpio_out and gpio_in need to be shorted externally in order for this
+ * test driver to work for the GPIO monitoring. The test driver has been
+ * tested on Jetson AGX Xavier platform by shorting pin 32 and 16 on 40 pin
+ * header.
+ *
+ * Device tree snippet to activate this driver:
+ *	tegra_hte_test {
+ *		compatible = "nvidia,tegra194-hte-test";
+ *		in-gpio = <&gpio_aon TEGRA194_AON_GPIO(BB, 1)>;
+ *		out-gpio = <&gpio_aon TEGRA194_AON_GPIO(BB, 0)>;
+ *		timestamps = <&tegra_hte_aon TEGRA194_AON_GPIO(BB, 1)>,
+ *			     <&tegra_hte_lic 0x19>;
+ *		timestamp-names = "hte-gpio", "hte-i2c-irq";
+ *		status = "okay";
+ *	};
+ *
+ * How to run test driver:
+ * - Load test driver.
+ * - For the GPIO, at regular interval gpio_out pin toggles triggering
+ *   HTE for rising edge on gpio_in pin.
+ *
+ * - For the LIC IRQ line, it uses 0x19 interrupt which is i2c controller 1.
+ * - Run i2cdetect -y 1 1>/dev/null, this command will generate i2c bus
+ *   transactions which creates timestamp data.
+ * - It prints below message for both the lines.
+ *   HW timestamp(<line id>:<ts seq number>): <timestamp>, edge: <edge>.
+ * - Unloading the driver disables and deallocate the HTE.
+ */
+
+static struct tegra_hte_test {
+	int gpio_in_irq;
+	struct device *pdev;
+	struct gpio_desc *gpio_in;
+	struct gpio_desc *gpio_out;
+	struct hte_ts_desc *desc;
+	struct timer_list timer;
+	struct kobject *kobj;
+} hte;
+
+static enum hte_return process_hw_ts(struct hte_ts_data *ts, void *p)
+{
+	char *edge;
+	struct hte_ts_desc *desc = p;
+
+	if (!ts || !p)
+		return HTE_CB_HANDLED;
+
+	if (ts->raw_level < 0)
+		edge = "Unknown";
+
+	pr_info("HW timestamp(%u: %llu): %llu, edge: %s\n",
+		desc->attr.line_id, ts->seq, ts->tsc,
+		(ts->raw_level >= 0) ? ((ts->raw_level == 0) ?
+					"falling" : "rising") : edge);
+
+	return HTE_CB_HANDLED;
+}
+
+static void gpio_timer_cb(struct timer_list *t)
+{
+	(void)t;
+
+	gpiod_set_value(hte.gpio_out, !gpiod_get_value(hte.gpio_out));
+	mod_timer(&hte.timer, jiffies + msecs_to_jiffies(8000));
+}
+
+static irqreturn_t tegra_hte_test_gpio_isr(int irq, void *data)
+{
+	(void)irq;
+	(void)data;
+
+	return IRQ_HANDLED;
+}
+
+static const struct of_device_id tegra_hte_test_of_match[] = {
+	{ .compatible = "nvidia,tegra194-hte-test"},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tegra_hte_test_of_match);
+
+static int tegra_hte_test_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+	int i, cnt;
+
+	dev_set_drvdata(&pdev->dev, &hte);
+	hte.pdev = &pdev->dev;
+
+	hte.gpio_out = gpiod_get(&pdev->dev, "out", 0);
+	if (IS_ERR(hte.gpio_out)) {
+		dev_err(&pdev->dev, "failed to get gpio out\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	hte.gpio_in = gpiod_get(&pdev->dev, "in", 0);
+	if (IS_ERR(hte.gpio_in)) {
+		dev_err(&pdev->dev, "failed to get gpio in\n");
+		ret = -EINVAL;
+		goto free_gpio_out;
+	}
+
+	ret = gpiod_direction_output(hte.gpio_out, 0);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to set output\n");
+		ret = -EINVAL;
+		goto free_gpio_in;
+	}
+
+	ret = gpiod_direction_input(hte.gpio_in);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to set input\n");
+		ret = -EINVAL;
+		goto free_gpio_in;
+	}
+
+	ret = gpiod_to_irq(hte.gpio_in);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to map GPIO to IRQ: %d\n", ret);
+		ret = -ENXIO;
+		goto free_gpio_in;
+	}
+
+	hte.gpio_in_irq = ret;
+	ret = request_irq(ret, tegra_hte_test_gpio_isr,
+			  IRQF_TRIGGER_RISING,
+			  "tegra_hte_gpio_test_isr", &hte);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to acquire IRQ\n");
+		ret = -ENXIO;
+		goto free_irq;
+	}
+
+	cnt = of_hte_req_count(hte.pdev);
+	if (cnt < 0)
+		goto free_irq;
+
+	dev_info(&pdev->dev, "Total requested lines:%d\n", cnt);
+
+	hte.desc = devm_kzalloc(hte.pdev, sizeof(*hte.desc) * cnt, GFP_KERNEL);
+	if (!hte.desc) {
+		ret = -ENOMEM;
+		goto free_irq;
+	}
+
+	for (i = 0; i < cnt; i++) {
+		if (i == 0)
+			/*
+			 * GPIO hte init, line_id and name will be parsed from
+			 * the device tree node. The edge_flag is implicitly
+			 * set by request_irq call. Only line_data is needed to be
+			 * set.
+			 */
+			hte_init_line_attr(&hte.desc[i], 0, 0, NULL,
+					   hte.gpio_in);
+		else
+			/*
+			 * same comment as above except that IRQ does not need
+			 * line data.
+			 */
+			hte_init_line_attr(&hte.desc[i], 0, 0, NULL, NULL);
+
+		ret = hte_ts_get(hte.pdev, &hte.desc[i], i);
+		if (ret)
+			goto ts_put;
+
+		ret = devm_hte_request_ts_ns(hte.pdev, &hte.desc[i],
+					     process_hw_ts, NULL,
+					     &hte.desc[i]);
+		if (ret) /* no need to ts_put, request API takes care */
+			goto free_irq;
+	}
+
+	timer_setup(&hte.timer, gpio_timer_cb, 0);
+	mod_timer(&hte.timer, jiffies + msecs_to_jiffies(5000));
+
+	return 0;
+
+ts_put:
+	cnt = i;
+	for (i = 0; i < cnt; i++)
+		hte_ts_put(&hte.desc[i]);
+free_irq:
+	free_irq(hte.gpio_in_irq, &hte);
+free_gpio_in:
+	gpiod_put(hte.gpio_in);
+free_gpio_out:
+	gpiod_put(hte.gpio_out);
+out:
+
+	return ret;
+}
+
+static int tegra_hte_test_remove(struct platform_device *pdev)
+{
+	(void)pdev;
+
+	free_irq(hte.gpio_in_irq, &hte);
+	gpiod_put(hte.gpio_in);
+	gpiod_put(hte.gpio_out);
+	del_timer(&hte.timer);
+
+	return 0;
+}
+
+static struct platform_driver tegra_hte_test_driver = {
+	.probe = tegra_hte_test_probe,
+	.remove = tegra_hte_test_remove,
+	.driver = {
+		.name = "tegra_hte_test",
+		.of_match_table = tegra_hte_test_of_match,
+	},
+};
+module_platform_driver(tegra_hte_test_driver);
+
+MODULE_AUTHOR("Dipen Patel <dipenp@nvidia.com>");
+MODULE_LICENSE("GPL");