i2c: i2c_gpio: Driver for software driven I2C using GPIO lines

This driver implements an I2C interface by driving two GPIO lines under
software control.

Change-Id: Ie49cc67aed6acb30086ee851041fe2470da241cf
Signed-off-by: Jon Medhurst <tixy@linaro.org>

4 files changed, 309 insertions, 0 deletions

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 5968e936a..30d59fe24 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -112,6 +112,7 @@ config I2C_BITBANG
 	help
 	  Enable library used for software driven (bit banging) I2C support
 
+source "drivers/i2c/Kconfig.gpio"
 
 config I2C_INIT_PRIORITY
 	int
diff --git a/drivers/i2c/Kconfig.gpio b/drivers/i2c/Kconfig.gpio
new file mode 100644
index 000000000..4501d1f87
--- /dev/null
+++ b/drivers/i2c/Kconfig.gpio
@@ -0,0 +1,158 @@
+#
+# Copyright (c) 2017 Linaro Ltd.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+config I2C_GPIO
+	bool "GPIO bit banging I2C support"
+	depends on I2C
+	select I2C_BITBANG
+	default n
+	help
+	  Enable software driven (bit banging) I2C support using GPIO pins
+
+# ---------- Port 0 ----------
+
+config I2C_GPIO_0
+	bool "Enable GPIO Bit Bang I2C device 0"
+	default n
+	depends on I2C_GPIO
+	help
+	  This tells the driver to configure the I2C device at boot, depending
+	  on the additional configuration options below.
+
+config I2C_GPIO_0_NAME
+	string "GPIO Bit Bang I2C device 0 device name"
+	default "I2C_0"
+	depends on I2C_GPIO_0
+	help
+	  This is the device name for the I2C device, and is included in the
+	  device struct.
+
+config I2C_GPIO_0_GPIO
+	string "Bit Bang I2C device 0 GPIO name"
+	depends on I2C_GPIO_0
+	help
+	  This is the name of the GPIO device that controls the I2C lines.
+
+config I2C_GPIO_0_SCL_PIN
+	int "Bit Bang I2C device 0 GPIO pin number for SCL"
+	depends on I2C_GPIO_0
+	help
+	  This is the GPIO pin number for the I2S SCL line
+
+config I2C_GPIO_0_SDA_PIN
+	int "Bit Bang I2C device 0 GPIO pin number for SDA"
+	depends on I2C_GPIO_0
+	help
+	  This is the GPIO pin number for the I2S SDA line
+
+# ---------- Port 1 ----------
+
+config I2C_GPIO_1
+	bool "Enable GPIO Bit Bang I2C device 1"
+	default n
+	depends on I2C_GPIO
+	help
+	  This tells the driver to configure the I2C device at boot, depending
+	  on the additional configuration options below.
+
+config I2C_GPIO_1_NAME
+	string "Bit Bang I2C device 1 device name"
+	default "I2C_1"
+	depends on I2C_GPIO_1
+	help
+	  This is the device name for the I2C device, and is included in the
+	  device struct.
+
+config I2C_GPIO_1_GPIO
+	string "Bit Bang I2C device 1 GPIO name"
+	depends on I2C_GPIO_1
+	help
+	  This is the name of the GPIO device that controls the I2C lines.
+
+config I2C_GPIO_1_SCL_PIN
+	int "Bit Bang I2C device 1 GPIO pin number for SCL"
+	depends on I2C_GPIO_1
+	help
+	  This is the GPIO pin number for the I2S SCL line
+
+config I2C_GPIO_1_SDA_PIN
+	int "Bit Bang I2C device 1 GPIO pin number for SDA"
+	depends on I2C_GPIO_1
+	help
+	  This is the GPIO pin number for the I2S SDA line
+
+# ---------- Port 2 ----------
+
+config I2C_GPIO_2
+	bool "Enable GPIO Bit Bang I2C device 2"
+	default n
+	depends on I2C_GPIO
+	help
+	  This tells the driver to configure the I2C device at boot, depending
+	  on the additional configuration options below.
+
+config I2C_GPIO_2_NAME
+	string "Bit Bang I2C device 2 device name"
+	default "I2C_2"
+	depends on I2C_GPIO_2
+	help
+	  This is the device name for the I2C device, and is included in the
+	  device struct.
+
+config I2C_GPIO_2_GPIO
+	string "Bit Bang I2C device 2 GPIO name"
+	depends on I2C_GPIO_2
+	help
+	  This is the name of the GPIO device that controls the I2C lines.
+
+config I2C_GPIO_2_SCL_PIN
+	int "Bit Bang I2C device 2 GPIO pin number for SCL"
+	depends on I2C_GPIO_2
+	help
+	  This is the GPIO pin number for the I2S SCL line
+
+config I2C_GPIO_2_SDA_PIN
+	int "Bit Bang I2C device 2 GPIO pin number for SDA"
+	depends on I2C_GPIO_2
+	help
+	  This is the GPIO pin number for the I2S SDA line
+
+# ---------- Port 3 ----------
+
+config I2C_GPIO_3
+	bool "Enable GPIO Bit Bang I2C device 3"
+	default n
+	depends on I2C_GPIO
+	help
+	  This tells the driver to configure the I2C device at boot, depending
+	  on the additional configuration options below.
+
+config I2C_GPIO_3_NAME
+	string "Bit Bang I2C device 3 device name"
+	default "I2C_3"
+	depends on I2C_GPIO_3
+	help
+	  This is the device name for the I2C device, and is included in the
+	  device struct.
+
+config I2C_GPIO_3_GPIO
+	string "Bit Bang I2C device 3 GPIO name"
+	depends on I2C_GPIO_3
+	help
+	  This is the name of the GPIO device that controls the I2C lines.
+
+config I2C_GPIO_3_SCL_PIN
+	int "Bit Bang I2C device 3 GPIO pin number for SCL"
+	depends on I2C_GPIO_3
+	help
+	  This is the GPIO pin number for the I2S SCL line
+
+config I2C_GPIO_3_SDA_PIN
+	int "Bit Bang I2C device 3 GPIO pin number for SDA"
+	depends on I2C_GPIO_3
+	help
+	  This is the GPIO pin number for the I2S SDA line
+
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index f500583a7..b3db3e81d 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -1,6 +1,7 @@
 obj-$(CONFIG_I2C_ATMEL_SAM3) += i2c_atmel_sam3.o
 obj-$(CONFIG_I2C_BITBANG) += i2c_bitbang.o
 obj-$(CONFIG_I2C_DW) += i2c_dw.o
+obj-$(CONFIG_I2C_GPIO) += i2c_gpio.o
 obj-$(CONFIG_I2C_MCUX) += i2c_mcux.o
 obj-$(CONFIG_I2C_NRF5) += i2c_nrf5.o
 obj-$(CONFIG_I2C_QMSI) += i2c_qmsi.o
diff --git a/drivers/i2c/i2c_gpio.c b/drivers/i2c/i2c_gpio.c
new file mode 100644
index 000000000..3d69e0c1d
--- /dev/null
+++ b/drivers/i2c/i2c_gpio.c
@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2017 Linaro Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Driver for software driven I2C using GPIO lines
+ *
+ * This driver implements an I2C interface by driving two GPIO lines under
+ * software control. The GPIO pins used must be preconfigured to to a suitable
+ * state, i.e. the SDA pin as open-colector/open-drain with a pull-up resistor
+ * (possibly as an external component attached to the pin). When the SDA pin
+ * is read it must return the state of the physical hardware line, not just the
+ * last state written to it for output.
+ *
+ * The SCL pin should be configued in the same manner as SDA, or, if it is known
+ * that the hardware attached to pin doesn't attempt clock stretching, then the
+ * SCL pin may be a push/pull output.
+ */
+
+#include <device.h>
+#include <errno.h>
+#include <gpio.h>
+#include <i2c.h>
+#include <i2c_bitbang.h>
+
+/* Driver config */
+struct i2c_gpio_config {
+	char *gpio_name;
+	u8_t scl_pin;
+	u8_t sda_pin;
+};
+
+/* Driver instance data */
+struct i2c_gpio_context {
+	struct i2c_bitbang bitbang;	/* Bit-bang library data */
+	struct device *gpio;		/* GPIO used for I2C lines */
+	u8_t scl_pin;			/* Pin on gpio used for SCL line */
+	u8_t sda_pin;			/* Pin on gpio used for SDA line */
+};
+
+static void i2c_gpio_set_scl(void *io_context, int state)
+{
+	struct i2c_gpio_context *context = io_context;
+
+	gpio_pin_write(context->gpio, context->scl_pin, state);
+}
+
+static void i2c_gpio_set_sda(void *io_context, int state)
+{
+	struct i2c_gpio_context *context = io_context;
+
+	gpio_pin_write(context->gpio, context->sda_pin, state);
+}
+
+static int i2c_gpio_get_sda(void *io_context)
+{
+	struct i2c_gpio_context *context = io_context;
+	u32_t state = 1; /* Default high as that would be a NACK */
+
+	gpio_pin_read(context->gpio, context->sda_pin, &state);
+	return state;
+}
+
+static const struct i2c_bitbang_io io_fns = {
+	.set_scl = &i2c_gpio_set_scl,
+	.set_sda = &i2c_gpio_set_sda,
+	.get_sda = &i2c_gpio_get_sda,
+};
+
+static int i2c_gpio_configure(struct device *dev, u32_t dev_config)
+{
+	struct i2c_gpio_context *context = dev->driver_data;
+
+	return i2c_bitbang_configure(&context->bitbang, dev_config);
+}
+
+static int i2c_gpio_transfer(struct device *dev, struct i2c_msg *msgs,
+				u8_t num_msgs, u16_t slave_address)
+{
+	struct i2c_gpio_context *context = dev->driver_data;
+
+	return i2c_bitbang_transfer(&context->bitbang, msgs, num_msgs,
+							slave_address);
+}
+
+static struct i2c_driver_api api = {
+	.configure = i2c_gpio_configure,
+	.transfer = i2c_gpio_transfer,
+};
+
+static int i2c_gpio_init(struct device *dev)
+{
+	struct i2c_gpio_context *context = dev->driver_data;
+	const struct i2c_gpio_config *config = dev->config->config_info;
+
+	context->gpio = device_get_binding(config->gpio_name);
+	if (!context->gpio) {
+		return -EINVAL;
+	}
+	context->sda_pin = config->sda_pin;
+	context->scl_pin = config->scl_pin;
+
+	i2c_bitbang_init(&context->bitbang, &io_fns, context);
+
+	/*
+	 * Set driver_api at very end of init so if we return early with error
+	 * then the device can't be found later by device_get_binding. This is
+	 * important because driver framework ignores errors from init
+	 * functions.
+	 */
+	dev->driver_api = &api;
+
+	return 0;
+}
+
+#define	DEFINE_I2C_GPIO(_num)						\
+									\
+static struct i2c_gpio_context i2c_gpio_dev_data_##_num;		\
+									\
+static const struct i2c_gpio_config i2c_gpio_dev_cfg_##_num = {		\
+	.gpio_name	= CONFIG_I2C_GPIO_##_num##_GPIO,		\
+	.scl_pin	= CONFIG_I2C_GPIO_##_num##_SCL_PIN,		\
+	.sda_pin	= CONFIG_I2C_GPIO_##_num##_SDA_PIN,		\
+};									\
+									\
+DEVICE_INIT(i2c_gpio_##_num, CONFIG_I2C_GPIO_##_num##_NAME,		\
+	    i2c_gpio_init,						\
+	    &i2c_gpio_dev_data_##_num,					\
+	    &i2c_gpio_dev_cfg_##_num,					\
+	    PRE_KERNEL_2, CONFIG_I2C_INIT_PRIORITY)
+
+#ifdef CONFIG_I2C_GPIO_0
+DEFINE_I2C_GPIO(0);
+#endif
+
+#ifdef CONFIG_I2C_GPIO_1
+DEFINE_I2C_GPIO(1);
+#endif
+
+#ifdef CONFIG_I2C_GPIO_2
+DEFINE_I2C_GPIO(2);
+#endif
+
+#ifdef CONFIG_I2C_GPIO_3
+DEFINE_I2C_GPIO(3);
+#endif