Bluetooth: hci: h4: use GPIO reset for nrf52840_pca10090 controllers

This patch adds support to the nRF9160 for using a dedicated
GPIO pin to reset controllers running on nrf52840_pca10090.

It resets the controller before opening the H4 device, and it
delays the controller from booting until all bytes traveling
to the host have been received and drained from the UART,
thus ensuring that communication can begin from a clean state.

Signed-off-by: Emanuele Di Santo <[email protected]>
Signed-off-by: Carles Cufi <[email protected]>

Author: lemrey

boards/arm/nrf9160_pca10090/CMakeLists.txt

@@ -0,0 +1,7 @@
+# Copyright (c) 2019 Nordic Semiconductor ASA.
+# SPDX-License-Identifier: Apache-2.0
+
+if(CONFIG_BOARD_NRF52840_GPIO_RESET)
+  zephyr_library()
+  zephyr_library_sources(nrf52840_reset.c)
+endif()

boards/arm/nrf9160_pca10090/Kconfig

@@ -6,4 +6,23 @@
 
 if BOARD_NRF9160_PCA10090 || BOARD_NRF9160_PCA10090NS
 
+config BOARD_NRF52840_GPIO_RESET
+        bool "Use nRF52840 PCA10090 GPIO reset pin"
+	default y if BT_H4
+        help
+          Use a GPIO pin to reset the nRF52840 controller and let it wait
+          until all bytes traveling to the H4 device have been received
+          and drained, thus ensuring communication can begin correctly.
+
+if BOARD_NRF52840_GPIO_RESET
+
+config BOARD_NRF52840_GPIO_RESET_PIN
+        int "Reset pin"
+        range 17 23
+        default 23
+        help
+          GPIO pin on the nRF9160 used to reset the nRF52840.
+
+endif
+
 endif # BOARD_NRF9160_PCA10090 || BOARD_NRF9160_PCA10090NS

boards/arm/nrf9160_pca10090/nrf52840_reset.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2019 Nordic Semiconductor ASA.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <gpio.h>
+#include <uart.h>
+#include <device.h>
+
+#define RESET_PIN CONFIG_BOARD_NRF52840_GPIO_RESET_PIN
+
+/* Must be a pin from 17 to 23.
+ * Only those can be connected to the nRF52840.
+ */
+BUILD_ASSERT_MSG(RESET_PIN > 16 && RESET_PIN < 24,
+		 "Selected pin is not connected to nRF52840");
+
+int bt_hci_transport_setup(struct device *h4)
+{
+	int err;
+	char c;
+	struct device *port;
+
+	port = device_get_binding(DT_GPIO_P0_DEV_NAME);
+	if (!port) {
+		return -EIO;
+	}
+
+	/* Pull the pin low before configuring it as output, to ensure that
+	 * it is driven to the correct level as soon as it is configured.
+	 */
+	err = gpio_pin_write(port, RESET_PIN, 0);
+	if (err) {
+		return err;
+	}
+
+	err = gpio_pin_configure(port, RESET_PIN, GPIO_DIR_OUT);
+	if (err) {
+		return err;
+	}
+
+	/* Reset the nRF52840 and let it wait until the pin is
+	 * pulled low again before running to main to ensure
+	 * that it won't send any data until the H4 device
+	 * is setup and ready to receive.
+	 */
+	err = gpio_pin_write(port, RESET_PIN, 1);
+	if (err) {
+		return err;
+	}
+
+	/* Wait for the nRF52840 peripheral to stop sending data.
+	 *
+	 * It is critical (!) to wait here, so that all bytes
+	 * on the lines are received and drained correctly.
+	 */
+	k_sleep(1);
+
+	/* Drain bytes */
+	while (uart_fifo_read(h4, &c, 1)) {
+		continue;
+	}
+
+	/* We are ready, let the nRF52840 run to main */
+	err = gpio_pin_write(port, RESET_PIN, 0);
+	if (err) {
+		return err;
+	}
+
+	return 0;
+}