1 files changed, 421 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/arm/raspberrypi/i2c/i2c.c b/c/src/lib/libbsp/arm/raspberrypi/i2c/i2c.c
new file mode 100644
index 0000000000..14a2467001
--- /dev/null
+++ b/c/src/lib/libbsp/arm/raspberrypi/i2c/i2c.c
@@ -0,0 +1,421 @@
+/**
+ * @file i2c.c
+ *
+ * @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. */
+      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;
+  uint32_t 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 );
+}