[RFC 07/11] gpio: tegra186: Add HTE in gpio-tegra186 driver

[Dipen Patel <dipenp@nvidia.com>]

Tegra194 AON GPIO controller with the use of its internal hardware
timestamping engine (HTE) also known as GTE can timestamp its GPIO
lines through system counter. This patch implements two callbacks
which are essential for the gpio consumers that want such HTE
functionality. The callbacks details can be found at
include/gpio/driver.h.

Since AON GPIO controller depends on HTE engine, it creates hardware
dependency between controller and AON HTE provider. To express that,
the optional devicetree property is introduced for AON GPIO controller.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
---
 .../bindings/gpio/nvidia,tegra186-gpio.txt    |  7 ++
 drivers/gpio/gpio-tegra186.c                  | 78 +++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt b/Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt
index adff16c71d21..00a3e47ab560 100644
--- a/Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt
@@ -127,6 +127,12 @@ Required properties:
             - 8: Active low level-sensitive.
             Valid combinations are 1, 2, 3, 4, 8.
 
+Optional properties:
+- timestamp-engine
+    AON GPIO controller has timestamp engine which can hardware timestamp
+    GPIO configured as input and IRQ. This property specifies hardware
+    timestamp engine (HTE) device-tree node.
+
 Example:
 
 #include <dt-bindings/interrupt-controller/irq.h>
@@ -162,4 +168,5 @@ gpio@c2f0000 {
 	#gpio-cells = <2>;
 	interrupt-controller;
 	#interrupt-cells = <2>;
+	timestamp-engine = <&tegra_hte_aon>;
 };
diff --git a/drivers/gpio/gpio-tegra186.c b/drivers/gpio/gpio-tegra186.c
index 05974b760796..4962d7de73f1 100644
--- a/drivers/gpio/gpio-tegra186.c
+++ b/drivers/gpio/gpio-tegra186.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
+#include <linux/hte.h>
 
 #include <dt-bindings/gpio/tegra186-gpio.h>
 #include <dt-bindings/gpio/tegra194-gpio.h>
@@ -34,6 +35,7 @@
 #define  TEGRA186_GPIO_ENABLE_CONFIG_TRIGGER_LEVEL BIT(4)
 #define  TEGRA186_GPIO_ENABLE_CONFIG_DEBOUNCE BIT(5)
 #define  TEGRA186_GPIO_ENABLE_CONFIG_INTERRUPT BIT(6)
+#define  TEGRA186_GPIO_ENABLE_CONFIG_TIMESTAMP_FUNC BIT(7)
 
 #define TEGRA186_GPIO_DEBOUNCE_CONTROL 0x04
 #define  TEGRA186_GPIO_DEBOUNCE_CONTROL_THRESHOLD(x) ((x) & 0xff)
@@ -79,6 +81,7 @@ struct tegra_gpio {
 	struct irq_chip intc;
 	unsigned int num_irq;
 	unsigned int *irq;
+	struct device_node *hte_nd;
 
 	const struct tegra_gpio_soc *soc;
 
@@ -188,6 +191,65 @@ static int tegra186_gpio_direction_output(struct gpio_chip *chip,
 	return 0;
 }
 
+static int tegra186_gpio_timestamp_control(struct gpio_chip *chip,
+					   unsigned int offset,
+					   struct hte_ts_desc **hdesc,
+					   bool enable)
+{
+	struct tegra_gpio *gpio = gpiochip_get_data(chip);
+	void __iomem *base;
+	int value;
+	struct hte_ts_desc *desc;
+
+	if (!gpio->hte_nd)
+		return -ENOTSUPP;
+
+	base = tegra186_gpio_get_base(gpio, offset);
+	if (WARN_ON(base == NULL))
+		return -EINVAL;
+
+	value = readl(base + TEGRA186_GPIO_ENABLE_CONFIG);
+
+	if (enable) {
+		desc = hte_req_ts_by_dt_node(gpio->hte_nd, offset, NULL);
+		if (IS_ERR(desc))
+			return PTR_ERR(desc);
+
+		*hdesc = desc;
+		value |= TEGRA186_GPIO_ENABLE_CONFIG_TIMESTAMP_FUNC;
+	} else {
+		desc = *hdesc;
+		hte_release_ts(desc);
+		value &= ~TEGRA186_GPIO_ENABLE_CONFIG_TIMESTAMP_FUNC;
+	}
+
+	writel(value, base + TEGRA186_GPIO_ENABLE_CONFIG);
+	return 0;
+}
+
+static int tegra186_gpio_get_hw_timestamp(struct gpio_chip *chip, bool block,
+					  struct hte_ts_desc *hdesc, u64 *ts)
+{
+	struct hte_ts_data el;
+	int ret;
+
+	if (!hdesc || !ts)
+		return -EINVAL;
+
+	if (!block)
+		ret = hte_retrieve_ts_ns(hdesc, &el, 1);
+	else
+		/* Wait till timestamp is available */
+		ret = hte_retrieve_ts_ns_wait(hdesc, &el, 1);
+
+	if (ret)
+		return ret;
+
+	*ts = el.tsc;
+
+	return 0;
+}
+
 static int tegra186_gpio_get(struct gpio_chip *chip, unsigned int offset)
 {
 	struct tegra_gpio *gpio = gpiochip_get_data(chip);
@@ -605,6 +667,7 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 	struct device_node *np;
 	char **names;
 	int err;
+	phandle hte_ph;
 
 	gpio = devm_kzalloc(&pdev->dev, sizeof(*gpio), GFP_KERNEL);
 	if (!gpio)
@@ -730,6 +793,21 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 		offset += port->pins;
 	}
 
+	err = of_property_read_u32(gpio->gpio.of_node,
+				   "timestamp-engine", &hte_ph);
+	if (!err) {
+		gpio->hte_nd = of_find_node_by_phandle(hte_ph);
+		if (!gpio->hte_nd)
+			return -ENOSYS;
+
+		gpio->gpio.timestamp_control = tegra186_gpio_timestamp_control;
+		gpio->gpio.get_hw_timestamp = tegra186_gpio_get_hw_timestamp;
+
+		of_node_put(gpio->hte_nd);
+	} else {
+		gpio->hte_nd = NULL;
+	}
+
 	platform_set_drvdata(pdev, gpio);
 
 	err = devm_gpiochip_add_data(&pdev->dev, &gpio->gpio, gpio);
-- 
2.17.1