/**
* @file
*
* @ingroup raspberrypi_i2c
*
* @brief Support for the I2C bus on the Raspberry Pi GPIO P1 header (model A/B)
* and GPIO J8 header on model B+.
*/
/*
* Copyright (c) 2014-2015 Andre Marques <andre.lousa.marques at gmail.com>
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
/*
* STATUS:
* - 10-bit slave addressing untested
*/
#include <bsp.h>
#include <bsp/raspberrypi.h>
#include <bsp/gpio.h>
#include <bsp/rpi-gpio.h>
#include <bsp/irq.h>
#include <bsp/i2c.h>
#include <assert.h>
#define TRANSFER_COUNT(buffer_size) (buffer_size + 0xFFFE) / 0xFFFF
#define ADJUST_TRANSFER_SIZE(transfer_count, remaining_bytes) \
transfer_count > 1 ? 0xFFFF : (remaining_bytes & 0xFFFF)
#define I2C_POLLING(condition) \
while ( condition ) { \
; \
}
/**
* @brief Object containing relevant information about an I2C bus.
*
* Encapsulates relevant data for a I2C bus transfer.
*/
typedef struct
{
i2c_bus base;
uint32_t input_clock;
rtems_id task_id;
/* Remaining bytes to read/write on the current bus transfer. */
uint32_t remaining_bytes;
/* Each transfer has a limit of 0xFFFF bytes, hence larger transfers
* have to be divided. Each transfer implies a stop condition, signaled
* automatically by the BSC controller. */
uint32_t remaining_transfers;
uint8_t *current_buffer;
uint32_t current_buffer_size;
bool read_transfer;
} rpi_i2c_bus;
static int rpi_i2c_bus_transfer(rpi_i2c_bus *bus)
{
while ( bus->remaining_bytes >= 1 ) {
/* If reading. */
if ( bus->read_transfer ) {
/* Poll RXD bit until there is data on the RX FIFO to read. */
I2C_POLLING((BCM2835_REG(BCM2835_I2C_S) & (1 << 5)) == 0);
/* Read data from the RX FIFO. */
(*(uint8_t *) bus->current_buffer) = BCM2835_REG(BCM2835_I2C_FIFO) & 0xFF;
++bus->current_buffer;
/* Check for acknowledgment or clock stretching errors. */
if (
(BCM2835_REG(BCM2835_I2C_S) & (1 << 8)) ||
(BCM2835_REG(BCM2835_I2C_S) & (1 << 9))
) {
return -EIO;
}
}
/* If writing. */
else {
/* If using the I2C bus in interrupt-driven mode. */
#if I2C_IO_MODE == 1
/* Generate interrupts on the TXW bit condition. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 9);
/* Sleep until the TX FIFO has free space for a new write. */
bus->task_id = rtems_task_self();
if (
rtems_event_transient_receive(RTEMS_WAIT, bus->base.timeout) !=
RTEMS_SUCCESSFUL
) {
rtems_event_transient_clear();
return -ETIMEDOUT;
}
/* If using the bus in polling mode. */
#else
/* Poll TXW bit until there is space available to write. */
I2C_POLLING((BCM2835_REG(BCM2835_I2C_S) & (1 << 2)) == 0);
#endif
/* Write data to the TX FIFO. */
BCM2835_REG(BCM2835_I2C_FIFO) = (*(uint8_t *) bus->current_buffer);
++bus->current_buffer;
/* Check for acknowledgment or clock stretching errors. */
if (
(BCM2835_REG(BCM2835_I2C_S) & (1 << 8)) ||
(BCM2835_REG(BCM2835_I2C_S) & (1 << 9))
) {
return -EIO;
}
}
--bus->remaining_bytes;
--bus->current_buffer_size;
}
return 0;
}
static int rpi_i2c_setup_transfer(rpi_i2c_bus *bus)
{
int rv;
while ( bus->remaining_transfers > 0 ) {
/* Setup the byte size of the current transfer. */
bus->remaining_bytes = ADJUST_TRANSFER_SIZE(
bus->remaining_transfers,
bus->current_buffer_size
);
/* Set the DLEN register, which specifies how many data packets
* will be transferred. */
BCM2835_REG(BCM2835_I2C_DLEN) = bus->remaining_bytes;
/* Clear the acknowledgment and clock stretching error status. */
BCM2835_REG(BCM2835_I2C_S) |= (3 << 8);
/* Send start bit. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 7);
/* Check for an acknowledgment error. */
if ( (BCM2835_REG(BCM2835_I2C_S) & (1 << 8)) != 0 ) {
return -EIO;
}
rv = rpi_i2c_bus_transfer(bus);
if ( rv < 0 ) {
return rv;
}
/* Wait for the current transfer to finish. */
/* If using the I2C bus in interrupt-driven mode. */
#if I2C_IO_MODE == 1
/* Generate interrupts on the DONE bit condition. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 8);
if (
rtems_event_transient_receive(RTEMS_WAIT, bus->base.timeout) !=
RTEMS_SUCCESSFUL
) {
rtems_event_transient_clear();
return -ETIMEDOUT;
}
/* If using the bus in polling mode. */
#else
/* Poll DONE bit until all data has been sent. */
I2C_POLLING((BCM2835_REG(BCM2835_I2C_S) & (1 << 1)) == 0);
#endif
--bus->remaining_transfers;
}
return 0;
}
/* Handler function that is called on any I2C interrupt.
*
* There are 3 situations that can generate an interrupt:
*
* 1. Transfer (read/write) complete;
* 2. The TX FIFO has space for more data (during a write transfer);
* 3. The RX FIFO is full.
*
* Because the I2C FIFO has a 16 byte size, the 3. situation is not
* as useful to many applications as knowing that at least 1 byte can
* be read from the RX FIFO. For that reason this information is
* got through polling the RXD bit even in interrupt-driven mode.
*
* This leaves only 2 interrupts to be caught. At any given time
* when no I2C bus transfer is taking place no I2C interrupts are
* generated, and they do they are only enabled one at a time:
*
* - When trying to write, the 2. interrupt is enabled to signal that
* data can be written on the TX FIFO, avoiding data loss in case
* it is full. When caught the handler disables that interrupt from
* being generated and sends a waking event to the transfer task,
* which will allow the transfer process to continue
* (by writing to the TX FIFO);
*
* - When the transfer is done on the Raspberry side, the 1. interrupt is
* enabled for the device to signal it has finished the transfer as
* well. When caught the handler disables that interrupt from being
* generated and sends a waking event to the transfer task, marking
* the end of the transfer.
*/
#if I2C_IO_MODE == 1
static void i2c_handler(void *arg)
{
rpi_i2c_bus *bus = (rpi_i2c_bus *) arg;
/* If the current enabled interrupt is on the TXW condition, disable it. */
if ( (BCM2835_REG(BCM2835_I2C_C) & (1 << 9)) ) {
BCM2835_REG(BCM2835_I2C_C) &= ~(1 << 9);
}
/* If the current enabled interrupt is on the DONE condition, disable it. */
else if ( (BCM2835_REG(BCM2835_I2C_C) & (1 << 8)) ) {
BCM2835_REG(BCM2835_I2C_C) &= ~(1 << 8);
}
/* Allow the transfer process to continue. */
rtems_event_transient_send(bus->task_id);
}
#endif
static int rpi_i2c_transfer(i2c_bus *base, i2c_msg *msgs, uint32_t msg_count)
{
rpi_i2c_bus *bus = (rpi_i2c_bus *) base;
int rv = 0;
uint32_t i;
/* Perform an initial parse through the messages for the I2C_M_RECV_LEN flag,
* which the Pi seems to not support and the I2C framework expects the bus
* to provide as part of the I2C_FUNC_I2C functionality.
*
* It states that the slave device sends an initial byte containing the size
* of the transfer, and for this to work the Pi will likely require two
* transfers, with a stop-start condition in-between. */
for ( i = 0; i < msg_count; ++i ) {
if ( msgs[i].flags & I2C_M_RECV_LEN ) {
return -EINVAL;
}
}
for ( i = 0; i < msg_count; ++i ) {
/* Clear FIFOs. */
BCM2835_REG(BCM2835_I2C_C) |= (3 << 4);
/* Setup transfer. */
bus->current_buffer = msgs[i].buf;
bus->current_buffer_size = msgs[i].len;
bus->remaining_transfers = TRANSFER_COUNT(bus->current_buffer_size);
/* If the slave uses 10-bit addressing. */
if ( msgs[i].flags & I2C_M_TEN ) {
/* Write the 8 least-significative bits of the slave address
* to the bus FIFO. */
BCM2835_REG(BCM2835_I2C_FIFO) = msgs[i].addr & 0xFF;
/* Address slave device, with the 2 most-significative bits at the end. */
BCM2835_REG(BCM2835_I2C_A) = (0x1E << 2) | (msgs[i].addr >> 8);
}
/* If using the regular 7-bit slave addressing. */
else {
/* Address slave device. */
BCM2835_REG(BCM2835_I2C_A) = msgs[i].addr;
}
if ( msgs[i].flags & I2C_M_RD ) {
/* If the slave uses 10-bit addressing. */
if ( msgs[i].flags & I2C_M_TEN ) {
/* 10-bit addressing setup for a read transfer. */
BCM2835_REG(BCM2835_I2C_DLEN) = 1;
/* Set write bit. */
BCM2835_REG(BCM2835_I2C_C) &= ~(1 << 0);
/* Send start bit. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 7);
/* Poll the TA bit until the transfer has started. */
I2C_POLLING((BCM2835_REG(BCM2835_I2C_S) & (1 << 0)) == 0);
}
/* Set read bit. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 0);
bus->read_transfer = true;
}
else if ( msgs[i].flags == 0 || msgs[i].flags == I2C_M_TEN ) {
/* If the slave uses 10-bit addressing. */
if ( msgs[i].flags & I2C_M_TEN ) {
/* 10-bit addressing setup for a write transfer. */
bus->current_buffer_size += 1;
bus->remaining_transfers = TRANSFER_COUNT(bus->current_buffer_size);
}
/* Set write bit. */
BCM2835_REG(BCM2835_I2C_C) &= ~(1 << 0);
bus->read_transfer = false;
}
rv = rpi_i2c_setup_transfer(bus);
if ( rv < 0 ) {
return rv;
}
}
return rv;
}
/* Calculates a clock divider to be used with the BSC core clock rate
* to set a I2C clock rate the closest (<=) to a desired frequency. */
static int rpi_i2c_set_clock(i2c_bus *base, unsigned long clock)
{
rpi_i2c_bus *bus = (rpi_i2c_bus *) base;
uint32_t clock_rate;
uint16_t divider;
/* Calculates an initial clock divider. */
divider = BSC_CORE_CLK_HZ / clock;
clock_rate = BSC_CORE_CLK_HZ / divider;
/* If the resulting clock rate is greater than desired, try the next greater
* divider. */
while ( clock_rate > clock ) {
++divider;
clock_rate = BSC_CORE_CLK_HZ / divider;
}
/* Set clock divider. */
BCM2835_REG(BCM2835_I2C_DIV) = divider;
bus->input_clock = clock_rate;
return 0;
}
static void rpi_i2c_destroy(i2c_bus *base)
{
rpi_i2c_bus *bus = (rpi_i2c_bus *) base;
i2c_bus_destroy_and_free(&bus->base);
}
int rpi_i2c_register_bus(
const char *bus_path,
uint32_t bus_clock
) {
#if I2C_IO_MODE == 1
rtems_status_code sc;
#endif
rpi_i2c_bus *bus;
int rv;
bus = (rpi_i2c_bus *) i2c_bus_alloc_and_init(sizeof(*bus));
if ( bus == NULL ) {
return -1;
}
/* Enable the I2C BSC interface. */
BCM2835_REG(BCM2835_I2C_C) |= (1 << 15);
/* If the access to the bus is configured to be interrupt-driven. */
#if I2C_IO_MODE == 1
bus->task_id = rtems_task_self();
sc = rtems_interrupt_handler_install(
BCM2835_IRQ_ID_I2C,
NULL,
RTEMS_INTERRUPT_UNIQUE,
(rtems_interrupt_handler) i2c_handler,
bus
);
if ( sc != RTEMS_SUCCESSFUL ) {
return -EIO;
}
#endif
rv = rpi_i2c_set_clock(&bus->base, bus_clock);
if ( rv < 0 ) {
(*bus->base.destroy)(&bus->base);
return -1;
}
bus->base.transfer = rpi_i2c_transfer;
bus->base.set_clock = rpi_i2c_set_clock;
bus->base.destroy = rpi_i2c_destroy;
bus->base.functionality = I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR;
return i2c_bus_register(&bus->base, bus_path);
}
void rpi_i2c_init(void)
{
/* Enable the I2C interface on the Raspberry Pi. */
rtems_gpio_initialize();
assert ( rpi_gpio_select_i2c() == RTEMS_SUCCESSFUL );
}
