bsp/aarch64/raspberrypi: Add I2C Support

- Implements polling-based I2C communication.
- Supports three independent I2C master controllers.
- Adds support for 10-bit addressing mode.

bsps/aarch64/raspberrypi/i2c/raspberrypi-i2c.c

@@ -0,0 +1,361 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup raspberrypi_4_i2c
+ *
+ * @brief I2C Driver
+ */
+
+/*
+ * Copyright (C) 2025 Shaunak Datar
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <bsp/irq.h>
+#include <bsp/raspberrypi-i2c.h>
+#include <bsp/raspberrypi.h>
+#include <bsp/rpi-gpio.h>
+#include <dev/i2c/i2c.h>
+
+#define C_REG( bus ) BCM2835_REG( ( bus )->base_address + BCM2711_I2C_CONTROL )
+#define C_I2CEN ( 1 << 15 )
+#define C_INTR ( 1 << 10 )
+#define C_INTT ( 1 << 9 )
+#define C_INTD ( 1 << 8 )
+#define C_ST ( 1 << 7 )
+#define C_CLEAR ( 1 << 5 )
+#define C_READ ( 1 << 0 )
+
+#define BSC_CORE_CLK_HZ 150000000
+
+#define S_REG( bus ) BCM2835_REG( ( bus )->base_address + BCM2711_I2C_STATUS )
+#define S_CLKT ( 1 << 9 )
+#define S_ERR ( 1 << 8 )
+#define S_RXF ( 1 << 7 )
+#define S_TXE ( 1 << 6 )
+#define S_RXD ( 1 << 5 )
+#define S_TXD ( 1 << 4 )
+#define S_RXR ( 1 << 3 )
+#define S_TXW ( 1 << 2 )
+#define S_DONE ( 1 << 1 )
+#define S_TA ( 1 << 0 )
+#define S_ERROR ( S_CLKT | S_ERR | S_DONE )
+
+typedef struct {
+  i2c_bus                 base;
+  uint32_t                input_clock;
+  uintptr_t               base_address;
+  raspberrypi_bsc_masters device;
+  uint32_t                remaining_bytes;
+  uint32_t                remaining_transfers;
+  uint8_t                *current_buffer;
+  uint32_t                current_buffer_size;
+  bool                    read_transfer;
+} raspberrypi_i2c_bus;
+
+static int i2c_polling_read( raspberrypi_i2c_bus *bus )
+{
+  while ( !( S_REG( bus ) & S_DONE ) && ( bus->remaining_bytes > 0 ) ) {
+    while ( ( S_REG( bus ) & S_RXD ) && ( bus->remaining_bytes > 0 ) ) {
+      *bus->current_buffer = BCM2835_REG(
+                               bus->base_address + BCM2711_I2C_FIFO
+                             ) &
+                             BCM2711_I2C_FIFO_MASK;
+      bus->current_buffer++;
+      bus->remaining_bytes--;
+
+      /* Check for errors */
+      if ( S_REG( bus ) & ( S_CLKT | S_ERR ) ) {
+        return -EIO;
+      }
+    }
+  }
+  return 0;
+}
+
+static int i2c_polling_write( raspberrypi_i2c_bus *bus )
+{
+  while ( !( S_REG( bus ) & S_DONE ) && ( bus->remaining_bytes > 0 ) ) {
+    while ( bus->remaining_bytes > 0 && ( S_REG( bus ) & S_TXD ) ) {
+      BCM2835_REG( bus->base_address + BCM2711_I2C_FIFO ) = *(
+        bus->current_buffer
+      );
+      bus->current_buffer++;
+      bus->remaining_bytes--;
+
+      /* Check for errors */
+      if ( S_REG( bus ) & ( S_CLKT | S_ERR ) ) {
+        return -EIO;
+      }
+    }
+  }
+  return 0;
+}
+
+static int rpi_i2c_bus_transfer( raspberrypi_i2c_bus *bus )
+{
+  int rv;
+  if ( bus->read_transfer ) {
+    rv = i2c_polling_read( bus );
+    if ( rv < 0 ) {
+      return rv;
+    }
+  } else {
+    rv = i2c_polling_write( bus );
+    if ( rv < 0 ) {
+      return rv;
+    }
+  }
+  if ( ( S_REG( bus ) & S_ERR ) || ( S_REG( bus ) & S_CLKT ) ||
+       ( bus->remaining_bytes != 0 ) ) {
+    return -EIO;
+  }
+
+  S_REG( bus ) = S_DONE;
+  return 0;
+}
+
+static void rpi_i2c_destroy( i2c_bus *base )
+{
+  raspberrypi_i2c_bus *bus = (raspberrypi_i2c_bus *) base;
+
+  i2c_bus_destroy_and_free( &bus->base );
+}
+
+static int rpi_i2c_set_clock( i2c_bus *base, unsigned long clock )
+{
+  raspberrypi_i2c_bus *bus = (raspberrypi_i2c_bus *) base;
+  uint32_t             clock_rate;
+  uint16_t             divider;
+
+  divider = BSC_CORE_CLK_HZ / clock;
+
+  clock_rate = BSC_CORE_CLK_HZ / divider;
+
+  while ( clock_rate > clock ) {
+    ++divider;
+    clock_rate = BSC_CORE_CLK_HZ / divider;
+  }
+
+  BCM2835_REG( bus->base_address + BCM2711_I2C_DIV ) = divider;
+
+  return 0;
+}
+
+static int rpi_i2c_setup_and_transfer( raspberrypi_i2c_bus *bus )
+{
+  int rv;
+  while ( bus->remaining_transfers > 0 ) {
+    bus->remaining_bytes = bus->remaining_transfers > 1 ?
+                             BCM2711_I2C_DLEN_MASK :
+                             ( bus->current_buffer_size & BCM2711_I2C_DLEN_MASK
+                             );
+    BCM2835_REG( bus->base_address + BCM2711_I2C_DLEN ) = bus->remaining_bytes;
+    /* Clear the error bits before starting new transfer */
+    S_REG( bus )                                        = S_ERROR;
+
+    rv = rpi_i2c_bus_transfer( bus );
+
+    if ( rv < 0 ) {
+      return rv;
+    }
+
+    --bus->remaining_transfers;
+  }
+  return 0;
+}
+
+static int rpi_i2c_transfer( i2c_bus *base, i2c_msg *msgs, uint32_t msg_count )
+{
+  raspberrypi_i2c_bus *bus = (raspberrypi_i2c_bus *) base;
+  int                  rv  = 0;
+  uint32_t             i;
+  uint8_t              msbs;
+  int                  supported_flags = I2C_M_TEN | I2C_M_RD;
+
+  for ( i = 0; i < msg_count; i++ ) {
+    if ( msgs[ i ].len == 0 || msgs[ i ].buf == NULL ) {
+      return -EINVAL;
+    }
+
+    if ( ( msgs[ i ].flags & ~supported_flags ) != 0 ) {
+      return -EINVAL;
+    }
+  }
+
+  for ( i = 0; i < msg_count; i++ ) {
+    bus->current_buffer      = msgs[ i ].buf;
+    bus->current_buffer_size = msgs[ i ].len;
+    bus->remaining_transfers = ( bus->current_buffer_size +
+                                 ( BCM2711_I2C_DLEN_MASK - 1 ) ) /
+                               BCM2711_I2C_DLEN_MASK;
+
+    /* 10-bit slave address */
+    if ( msgs[ i ].flags & I2C_M_TEN ) {
+      /* Add the 8 lsbs of the 10-bit slave address to the fifo register */
+      BCM2835_REG(
+        bus->base_address + BCM2711_I2C_FIFO
+      ) = msgs[ i ].addr & BCM2711_I2C_FIFO_MASK;
+
+      msbs = msgs[ i ].addr >> 8;
+      BCM2835_REG(
+        bus->base_address + BCM2711_I2C_SLAVE_ADDRESS
+      ) = BCM2711_10_BIT_ADDR_MASK | msbs;
+
+    } else {
+      BCM2835_REG(
+        bus->base_address + BCM2711_I2C_SLAVE_ADDRESS
+      ) = msgs[ i ].addr;
+    }
+
+    if ( msgs[ i ].flags & I2C_M_RD ) {
+      C_REG( bus )       |= C_CLEAR | C_READ | C_ST; // Read packet transfer
+      bus->read_transfer  = true;
+    } else {
+      C_REG( bus )       |= C_CLEAR | C_ST; // Write packet transfer
+      bus->read_transfer  = false;
+    }
+    /* Disable clock stretch timeout */
+    BCM2835_REG( bus->base_address + BCM2711_I2C_CLKT ) = 0;
+
+    rv = rpi_i2c_setup_and_transfer( bus );
+    if ( rv < 0 ) {
+      return rv;
+    }
+  }
+
+  return rv;
+}
+
+static rtems_status_code rpi_i2c_gpio_init(
+  raspberrypi_bsc_masters device,
+  raspberrypi_i2c_bus    *bus
+)
+{
+  switch ( device ) {
+    case raspberrypi_bscm0:
+      raspberrypi_gpio_set_function( 0, GPIO_AF0 );
+      raspberrypi_gpio_set_function( 1, GPIO_AF0 );
+      bus->base_address = BCM2711_I2C0_BASE;
+      break;
+    case raspberrypi_bscm1:
+      raspberrypi_gpio_set_function( 2, GPIO_AF0 );
+      raspberrypi_gpio_set_function( 3, GPIO_AF0 );
+      bus->base_address = BCM2711_I2C1_BASE;
+      break;
+    case raspberrypi_bscm3:
+      raspberrypi_gpio_set_function( 4, GPIO_AF5 );
+      raspberrypi_gpio_set_function( 5, GPIO_AF5 );
+      bus->base_address = BCM2711_I2C3_BASE;
+      break;
+    case raspberrypi_bscm4:
+      raspberrypi_gpio_set_function( 6, GPIO_AF5 );
+      raspberrypi_gpio_set_function( 7, GPIO_AF5 );
+      bus->base_address = BCM2711_I2C4_BASE;
+      break;
+    case raspberrypi_bscm5:
+      raspberrypi_gpio_set_function( 10, GPIO_AF5 );
+      raspberrypi_gpio_set_function( 11, GPIO_AF5 );
+      bus->base_address = BCM2711_I2C5_BASE;
+      break;
+    case raspberrypi_bscm6:
+      raspberrypi_gpio_set_function( 22, GPIO_AF5 );
+      raspberrypi_gpio_set_function( 23, GPIO_AF5 );
+      bus->base_address = BCM2711_I2C6_BASE;
+      break;
+    default:
+      return RTEMS_INVALID_ADDRESS;
+  }
+  return RTEMS_SUCCESSFUL;
+}
+
+static char *rpi_select_bus( raspberrypi_bsc_masters device )
+{
+  switch ( device ) {
+    case raspberrypi_bscm0:
+      return "/dev/i2c-0";
+    case raspberrypi_bscm1:
+      return "/dev/i2c-1";
+    case raspberrypi_bscm3:
+      return "/dev/i2c-3";
+    case raspberrypi_bscm4:
+      return "/dev/i2c-4";
+    case raspberrypi_bscm5:
+      return "/dev/i2c-5";
+    case raspberrypi_bscm6:
+      return "/dev/i2c-6";
+    default:
+      return NULL;
+  }
+}
+
+rtems_status_code rpi_i2c_init(
+  raspberrypi_bsc_masters device,
+  uint32_t                bus_clock
+)
+{
+  raspberrypi_i2c_bus *bus;
+  rtems_status_code    sc;
+  const char          *bus_path;
+
+  if ( device != raspberrypi_bscm0 && device != raspberrypi_bscm1 &&
+       device != raspberrypi_bscm3 && device != raspberrypi_bscm4 &&
+       device != raspberrypi_bscm5 && device != raspberrypi_bscm6 ) {
+    return RTEMS_INVALID_NUMBER;
+  }
+
+  bus_path = rpi_select_bus( device );
+  if ( bus_path == NULL ) {
+    return RTEMS_INVALID_NUMBER;
+  }
+
+  bus = (raspberrypi_i2c_bus *) i2c_bus_alloc_and_init( sizeof( *bus ) );
+  if ( bus == NULL ) {
+    return RTEMS_NO_MEMORY;
+  }
+
+  sc = rpi_i2c_gpio_init( device, bus );
+  if ( sc != RTEMS_SUCCESSFUL ) {
+    i2c_bus_destroy_and_free( &bus->base );
+    return sc;
+  }
+
+  /* Enable I2C */
+  C_REG( bus ) = C_CLEAR;
+  C_REG( bus ) = C_I2CEN;
+
+  sc = rpi_i2c_set_clock( &bus->base, bus_clock );
+  if ( sc != RTEMS_SUCCESSFUL ) {
+    i2c_bus_destroy_and_free( &bus->base );
+    return sc;
+  }
+
+  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 );
+}

bsps/aarch64/raspberrypi/include/bsp/raspberrypi-i2c.h

@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup raspberrypi_4_i2c
+ *
+ * @brief Raspberry Pi specific I2C definitions.
+ */
+
+/*
+ * Copyright (C) 2025 Shaunak Datar
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LIBBSP_AARCH64_RASPBERRYPI_I2C_H
+#define LIBBSP_AARCH64_RASPBERRYPI_I2C_H
+
+#include <bsp/raspberrypi.h>
+#include <bsp/rpi-gpio.h>
+#include <bsp/utility.h>
+#include <dev/i2c/i2c.h>
+
+/**
+ * @brief I2C controller instances on Raspberry Pi 4.
+ */
+typedef enum {
+  /**
+   * @brief BSC Master 0 (GPIO 0/1)
+   */
+  raspberrypi_bscm0,
+
+  /**
+   * @brief BSC Master 1 (GPIO 2/3)
+   */
+  raspberrypi_bscm1,
+
+  /**
+   * @brief BSC Master 3 (GPIO 4/5)
+   */
+  raspberrypi_bscm3,
+
+  /**
+   * @brief BSC Master 4 (GPIO 6/7)
+   */
+  raspberrypi_bscm4,
+
+  /**
+   * @brief BSC Master 5 (GPIO 10/11)
+   */
+  raspberrypi_bscm5,
+
+  /**
+   * @brief BSC Master 6 (GPIO 22/23)
+   */
+  raspberrypi_bscm6
+} raspberrypi_bsc_masters;
+
+/**
+ * @brief Initialize the I2C bus for a specified master.
+ *
+ * @param device The BSC master to initialize.
+ * @param bus_clock The desired bus clock frequency in Hz.
+ *
+ * @return RTEMS status code indicating success or failure.
+ */
+rtems_status_code rpi_i2c_init(
+  raspberrypi_bsc_masters device,
+  uint32_t                bus_clock
+);
+
+#endif /* LIBBSP_AARCH64_RASPBERRYPI_I2C_H */

bsps/aarch64/raspberrypi/include/bsp/raspberrypi.h

@@ -282,7 +282,6 @@
 #define BCM2711_SPI4_BASE ( RPI_PERIPHERAL_BASE + 0x204800 )
 #define BCM2711_SPI5_BASE ( RPI_PERIPHERAL_BASE + 0x204A00 )
 #define BCM2711_SPI6_BASE ( RPI_PERIPHERAL_BASE + 0x204C00 )
-
 /** @} */
 
 /**
@@ -290,7 +289,6 @@
  *
  * @{
  */
-
 #define BCM2711_CM_PWM_BASE ( RPI_PERIPHERAL_BASE + 0x00101000 )
 #define BCM2711_CM_PWM_CTL 0xA0
 #define BCM2711_CM_PWM_DIV 0xA4
@@ -299,7 +297,6 @@
 #define CM_PWM_CTL_BUSY BSP_BIT32( 7 )
 #define CM_PWM_CTL_ENAB BSP_BIT32( 4 )
 #define CM_PWM_DIV_MASK 0xFFF
-
 /** @} */
 
 /**
@@ -307,7 +304,6 @@
  *
  * @{
  */
-
 #define BCM2711_PWM0_BASE ( RPI_PERIPHERAL_BASE + 0x0020C000 )
 #define BCM2711_PWM1_BASE ( RPI_PERIPHERAL_BASE + 0x0020C800 )
 #define BCM2711_PWM_CONTROL 0x00
@@ -318,7 +314,30 @@
 #define BCM2711_PWM_FIFO 0x18
 #define BCM2711_PWM_RNG2 0x20
 #define BCM2711_PWM_DAT2 0x24
+/** @} */
 
+/**
+ * @name I2C Registers
+ *
+ * @{
+ */
+#define BCM2711_I2C0_BASE ( RPI_PERIPHERAL_BASE + 0x00205000 )
+#define BCM2711_I2C1_BASE ( RPI_PERIPHERAL_BASE + 0x00804000 )
+#define BCM2711_I2C3_BASE ( RPI_PERIPHERAL_BASE + 0x00205600 )
+#define BCM2711_I2C4_BASE ( RPI_PERIPHERAL_BASE + 0x00205800 )
+#define BCM2711_I2C5_BASE ( RPI_PERIPHERAL_BASE + 0x00205a80 )
+#define BCM2711_I2C6_BASE ( RPI_PERIPHERAL_BASE + 0x00205c00 )
+#define BCM2711_I2C_CONTROL 0x0
+#define BCM2711_I2C_STATUS 0x4
+#define BCM2711_I2C_DLEN 0x8
+#define BCM2711_I2C_SLAVE_ADDRESS 0xc
+#define BCM2711_I2C_FIFO 0x10
+#define BCM2711_I2C_DIV 0x14
+#define BCM2711_DELAY 0x18
+#define BCM2711_I2C_CLKT 0x1c
+#define BCM2711_I2C_FIFO_MASK 0xFF
+#define BCM2711_I2C_DLEN_MASK 0xFFFF
+#define BCM2711_10_BIT_ADDR_MASK 0x78
 /** @} */
 
 /**

spec/build/bsps/aarch64/raspberrypi/bspraspberrypi4.yml

@@ -67,6 +67,8 @@ links:
   uid: objwatchdog
 - role: build-dependency
   uid: objpwm
+- role: build-dependency
+  uid: obji2c
 source:
 - bsps/aarch64/raspberrypi/fdt/bsp_fdt.c
 - bsps/aarch64/raspberrypi/fdt/rpi4b_dtb.c

spec/build/bsps/aarch64/raspberrypi/obji2c.yml

@@ -0,0 +1,17 @@
+SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
+build-type: objects
+cflags: []
+copyrights:
+- Copyright (C) 2025 Shaunak Datar
+cppflags: []
+cxxflags: []
+enabled-by: true
+includes: []
+install:
+- destination: ${BSP_INCLUDEDIR}/bsp
+  source:
+  - bsps/aarch64/raspberrypi/include/bsp/raspberrypi-i2c.h
+links: []
+source:
+- bsps/aarch64/raspberrypi/i2c/raspberrypi-i2c.c
+type: build