path: root/nuttx/arch/arm/src/stm32/stm32_i2c.c

/************************************************************************************
 * arch/arm/src/stm32/stm32_i2c.c
 *
 *   Copyright (C) 2011 Uros Platise. All rights reserved.
 *   Author: Uros Platise <uros.platise@isotel.eu>
 *
 * With extensions, modifications by:
 *
 *   Author: Gregroy Nutt <gnutt@nuttx.org>
 *
 * 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.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * 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.
 *
 ************************************************************************************/

/* \file
 *  \author Uros Platise
 *  \brief STM32 I2C Hardware Layer - Device Driver
 * 
 * Supports:
 *  - Master operation, 100 kHz (standard) and 400 kHz (full speed)
 *  - Multiple instances (shared bus)
 *  - Interrupt based operation
 * 
 * Structure naming:
 *  - Device: structure as defined by the nuttx/i2c/i2c.h
 *  - Instance: represents each individual access to the I2C driver, obtained by
 *      the i2c_init(); it extends the Device structure from the nuttx/i2c/i2c.h; 
 *      Instance points to OPS, to common I2C Hardware private data and contains
 *      its own private data, as frequency, address, mode of operation (in the future)
 *  - Private: Private data of an I2C Hardware
 * 
 * \todo
 *  - Check for all possible deadlocks (as BUSY='1' I2C needs to be reset in HW using the I2C_CR1_SWRST)
 *  - SMBus support (hardware layer timings are already supported) and add SMBA gpio pin
 *  - Slave support with multiple addresses (on multiple instances):
 *      - 2 x 7-bit address or 
 *      - 1 x 10 bit adresses + 1 x 7 bit address (?)
 *      - plus the broadcast address (general call)
 *  - Multi-master support
 *  - DMA (to get rid of too many CPU wake-ups and interventions)
 *  - Be ready for IPMI
 **/

/************************************************************************************
 * Included Files
 ************************************************************************************/

#include <nuttx/config.h>
#include <nuttx/arch.h>
#include <nuttx/irq.h>
#include <nuttx/i2c.h>
#include <nuttx/kmalloc.h>
#include <arch/board/board.h>

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <semaphore.h>
#include <errno.h>
#include <debug.h>

#include "up_arch.h"

#include "stm32_rcc.h"
#include "stm32_i2c.h"
#include "stm32_waste.h"

#if defined(CONFIG_STM32_I2C1) || defined(CONFIG_STM32_I2C2)

/************************************************************************************
 * Pre-processor Definitions
 ************************************************************************************/
/* Configuration ********************************************************************/
/* Interrupt wait timeout in seconds and milliseconds */

#if !defined(CONFIG_STM32_I2CTIMEOSEC) && !defined(CONFIG_STM32_I2CTIMEOMS)
#  define  CONFIG_STM32_I2CTIMEOSEC 0
#  define CONFIG_STM32_I2CTIMEOMS   500   /* Default is 500 milliseconds */
#elif !defined(CONFIG_STM32_I2CTIMEOSEC)
#  define  CONFIG_STM32_I2CTIMEOSEC 0     /* User provided milliseconds */
#elif !defined(CONFIG_STM32_I2CTIMEOMS)
#  define CONFIG_STM32_I2CTIMEOMS   0     /* User provided seconds */
#endif

/* Debug ****************************************************************************/

#ifdef CONFIG_DEBUG_I2C
#  define i2cdbg dbg
#  ifdef CONFIG_DEBUG_I2CINTS
#    define intdbg lldbg
#  else
#    define intdbg(x...)
#  endif
#else
#  undef CONFIG_DEBUG_I2CINTS
#  define i2cdbg(x...)
#  define intdbg(x...)
#endif

/************************************************************************************
 * Private Types
 ************************************************************************************/

/* I2C Device Private Data */

struct stm32_i2c_priv_s
{
  uint32_t    base;        /* I2C base address */
  int         refs;        /* Referernce count */
  sem_t       sem_excl;    /* Mutual exclusion semaphore */
  sem_t       sem_isr;     /* Interrupt wait semaphore */
  volatile bool isr_wait;  /* Handshake to ignore unexpected interrupts */
    
  uint8_t     msgc;        /* Message count */
  struct i2c_msg_s *msgv;  /* Message list */
  uint8_t    *ptr;         /* Current message buffer */
  int         dcnt;        /* Current message length */
  uint16_t    flags;       /* Current message flags */

  uint32_t    status;      /* End of transfer SR2|SR1 status */
};

/* I2C Device, Instance */

struct stm32_i2c_inst_s
{
  struct i2c_ops_s        *ops;  /* Standard I2C operations */
  struct stm32_i2c_priv_s *priv; /* Common driver private data structure */
    
  uint32_t    frequency;         /* Frequency used in this instantiation */
  int         address;           /* Address used in this instantiation */
  uint16_t    flags;             /* Flags used in this instantiation */
};

/************************************************************************************
 * Private Data
 ************************************************************************************/

#ifdef CONFIG_STM32_I2C1
struct stm32_i2c_priv_s stm32_i2c1_priv =
{
  .base       = STM32_I2C1_BASE,
  .refs       = 0,
  .isr_wait   = false,
  .msgc       = 0,
  .msgv       = NULL,
  .ptr        = NULL,
  .dcnt       = 0,
  .flags      = 0,
  .status     = 0    
};
#endif

#ifdef CONFIG_STM32_I2C2
struct stm32_i2c_priv_s stm32_i2c2_priv =
{
  .base       = STM32_I2C2_BASE,
  .refs       = 0,
  .isr_wait   = false,
  .msgc       = 0,
  .msgv       = NULL,
  .ptr        = NULL,
  .dcnt       = 0,
  .flags      = 0,
  .status     = 0
};
#endif

/************************************************************************************
 * Private Functions
 ************************************************************************************/

/* Get register value by offset */

static inline uint16_t stm32_i2c_getreg(FAR struct stm32_i2c_priv_s *priv,
                                        uint8_t offset)
{
  return getreg16(priv->base + offset);
}

/* Put register value by offset */

static inline void stm32_i2c_putreg(FAR struct stm32_i2c_priv_s *priv, uint8_t offset,
                                    uint16_t value)
{
  putreg16(value, priv->base + offset);
}

/* Modify register value by offset */

static inline void stm32_i2c_modifyreg(FAR struct stm32_i2c_priv_s *priv,
                                       uint8_t offset, uint16_t clearbits,
                                       uint16_t setbits)
{
  modifyreg16(priv->base + offset, clearbits, setbits);
}

void inline stm32_i2c_sem_wait(FAR struct i2c_dev_s *dev)
{
  while (sem_wait(&((struct stm32_i2c_inst_s *)dev)->priv->sem_excl) != 0)
    {
      ASSERT(errno == EINTR);
    }
}

int inline stm32_i2c_sem_waitisr(FAR struct i2c_dev_s *dev)
{
  FAR struct stm32_i2c_priv_s *priv = ((struct stm32_i2c_inst_s *)dev)->priv;
  struct timespec abstime;
  irqstate_t flags;
  uint32_t regval;
  int ret;

  flags = irqsave();

  /* Enable I2C interrupts */

  regval  = stm32_i2c_getreg(priv, STM32_I2C_CR2_OFFSET);
  regval |= (I2C_CR2_ITERREN | I2C_CR2_ITEVFEN);
  stm32_i2c_putreg(priv, STM32_I2C_CR2_OFFSET, regval);

  do
    {
      /* Get the current time */

      (void)clock_gettime(CLOCK_REALTIME, &abstime);

      /* Calculate a time in the future */

#if CONFIG_STM32_I2CTIMEOSEC > 0
      abstime.tv_sec += CONFIG_STM32_I2CTIMEOSEC;
#endif
#if CONFIG_STM32_I2CTIMEOMS > 0
      abstime.tv_nsec += CONFIG_STM32_I2CTIMEOMS * 1000 * 1000;
      if (abstime.tv_nsec > 1000 * 1000 * 1000)
        {
          abstime.tv_sec++;
          abstime.tv_nsec -= 1000 * 1000 * 1000;
        }
#endif
      /* Wait until either the transfer is complete or the timeout expires */

      priv->isr_wait = true;
      ret = sem_timedwait(&priv->sem_isr, &abstime);
      priv->isr_wait = false;
    }
  while (ret != OK && errno == EINTR);

  /* Disable I2C interrupts */

  regval  = stm32_i2c_getreg(priv, STM32_I2C_CR2_OFFSET);
  regval &= ~I2C_CR2_ALLINTS;
  stm32_i2c_putreg(priv, STM32_I2C_CR2_OFFSET, regval);
  irqrestore(flags);
  return ret;
}

void inline stm32_i2c_sem_post(FAR struct i2c_dev_s *dev)
{
  sem_post( &((struct stm32_i2c_inst_s *)dev)->priv->sem_excl );
}

void inline stm32_i2c_sem_init(FAR struct i2c_dev_s *dev)
{
  sem_init( &((struct stm32_i2c_inst_s *)dev)->priv->sem_excl, 0, 1);
  sem_init( &((struct stm32_i2c_inst_s *)dev)->priv->sem_isr, 0, 0);
}

void inline stm32_i2c_sem_destroy(FAR struct i2c_dev_s *dev)
{
  sem_destroy( &((struct stm32_i2c_inst_s *)dev)->priv->sem_excl );
  sem_destroy( &((struct stm32_i2c_inst_s *)dev)->priv->sem_isr );
}

static void stm32_i2c_setclock(FAR struct stm32_i2c_priv_s *priv, uint32_t frequency)
{
  uint16_t cr1;
  uint16_t ccr;
  uint16_t trise;
  uint16_t freqmhz;
  uint16_t speed;

  /* Disable the selected I2C peripheral to configure TRISE */

  cr1 = stm32_i2c_getreg(priv, STM32_I2C_CR1_OFFSET);
  stm32_i2c_putreg(priv, STM32_I2C_CR1_OFFSET, cr1 & ~I2C_CR1_PE);

  /* Update timing and control registers */

  freqmhz = (uint16_t)(STM32_PCLK1_FREQUENCY / 1000000);
  ccr = 0;

  /* Configure speed in standard mode */

  if (frequency <= 100000)
    {
      /* Standard mode speed calculation */

      speed = (uint16_t)(STM32_PCLK1_FREQUENCY / (frequency << 1));

      /* The CCR fault must be >= 4 */

      if (speed < 4)
        {
          /* Set the minimum allowed value */

          speed = 4;  
        }
      ccr |= speed;

      /* Set Maximum Rise Time for standard mode */

      trise = freqmhz + 1; 
    }

  /* Configure speed in fast mode */

  else /* (frequency <= 400000) */
    {
      /* Fast mode speed calculation with Tlow/Thigh = 16/9 */

#ifdef CONFIG_I2C_DUTY16_9
      speed = (uint16_t)(STM32_PCLK1_FREQUENCY / (frequency * 25));

      /* Set DUTY and fast speed bits */

      ccr |= (I2C_CCR_DUTY|I2C_CCR_FS);
#else
      /* Fast mode speed calculation with Tlow/Thigh = 2 */

      speed = (uint16_t)(STM32_PCLK1_FREQUENCY / (frequency * 3));

      /* Set fast speed bit */

      ccr |= I2C_CCR_FS;
#endif

      /* Verify that the CCR speed value is nonzero */

      if (speed < 1)
        {
          /* Set the minimum allowed value */

          speed = 1;  
        }
      ccr |= speed;

      /* Set Maximum Rise Time for fast mode */

      trise = (uint16_t)(((freqmhz * 300) / 1000) + 1);  
    }

  /* Write the new values of the CCR and TRISE registers */

  stm32_i2c_putreg(priv, STM32_I2C_CCR_OFFSET, ccr);
  stm32_i2c_putreg(priv, STM32_I2C_TRISE_OFFSET, trise);

  /* Bit 14 of OAR1 must be configured and kept at 1 */

  stm32_i2c_putreg(priv, STM32_I2C_OAR1_OFFSET, I2C_OAR1_ONE);

  /* Re-enable the peripheral (or not) */

  stm32_i2c_putreg(priv, STM32_I2C_CR1_OFFSET, cr1);
}

static inline void stm32_i2c_sendstart(FAR struct stm32_i2c_priv_s *priv)
{
  /* Disable ACK on receive by default and generate START */

  stm32_i2c_modifyreg(priv, STM32_I2C_CR1_OFFSET, I2C_CR1_ACK, I2C_CR1_START);
}

static inline void stm32_i2c_clrstart(FAR struct stm32_i2c_priv_s *priv)
{
  /* "This [START] bit is set and cleared by software and cleared by hardware
   *  when start is sent or PE=0."  The bit must be cleared by software if the
   *  START is never sent.
   */

  stm32_i2c_modifyreg(priv, STM32_I2C_CR1_OFFSET, I2C_CR1_START, 0);
}

static inline void stm32_i2c_sendstop(FAR struct stm32_i2c_priv_s *priv)
{
  stm32_i2c_modifyreg(priv, STM32_I2C_CR1_OFFSET, I2C_CR1_ACK, I2C_CR1_STOP);
}

static inline uint32_t stm32_i2c_getstatus(FAR struct stm32_i2c_priv_s *priv)
{
  uint32_t status = stm32_i2c_getreg(priv, STM32_I2C_SR1_OFFSET);
  status |= (stm32_i2c_getreg(priv, STM32_I2C_SR2_OFFSET) << 16);
  return status;
}

/* FSMC must be disable while accessing I2C1 because it uses a common resource (LBAR) */

#if defined(CONFIG_STM32_FSMC) && defined (CONFIG_STM32_I2C1)
static inline uint32_t stm32_i2c_disablefsmc(FAR struct stm32_i2c_priv_s *priv)
{
  uint32_t ret = 0;
  uint32_t regval;

  /* Is this I2C1 */

#ifdef CONFIG_STM32_I2C2
  if (priv->base == STM32_I2C1_BASE)
#endif
    {
      /* Disable FSMC unconditionally */

      ret    = getreg32( STM32_RCC_AHBENR);
      regval = ret & ~RCC_AHBENR_FSMCEN;
      putreg32(regval, STM32_RCC_AHBENR);
    }
  return ret;
}

static inline void stm32_i2c_enablefsmc(uint32_t ahbenr)
{
  uint32_t regval;

  /* Enable AHB clocking to the FSMC only if it was previously enabled. */

  if ((ahbenr & RCC_AHBENR_FSMCEN) != 0)
    {
      regval  = getreg32( STM32_RCC_AHBENR);
      regval |= RCC_AHBENR_FSMCEN;
      putreg32(regval, STM32_RCC_AHBENR);
    }
}
#else
#  define stm32_i2c_disablefsmc() (0)
#  define stm32_i2c_enablefsmc(ahbenr)
#endif

/************************************************************************************
 * Interrupt Service Routines
 ************************************************************************************/

static int stm32_i2c_isr(struct stm32_i2c_priv_s * priv)
{
  uint32_t status = stm32_i2c_getstatus(priv);

#ifdef CONFIG_DEBUG_I2CINTS
  static uint32_t isr_count = 0;
  static uint32_t old_status = 0xFFFF;
  isr_count++;

  if (old_status != status)
    {
        intdbg("status = %8x, count=%d\n", status, isr_count); fflush(stdout);
        old_status = status;
    }
#endif
            
  /* Was start bit sent */
    
  if (status & I2C_SR1_SB)
    {
      /* Get run-time data */

      priv->ptr   = priv->msgv->buffer;
      priv->dcnt  = priv->msgv->length;
      priv->flags = priv->msgv->flags;

      /* Send address byte and define addressing mode */

      stm32_i2c_putreg(priv, STM32_I2C_DR_OFFSET,
                      (priv->flags & I2C_M_TEN) ?
                       0 :
                      ((priv->msgv->addr << 1) | (priv->flags & I2C_M_READ))
                      );

      /* Set ACK for receive mode */

      if (priv->dcnt > 1 && (priv->flags & I2C_M_READ) )
        {
          stm32_i2c_modifyreg(priv, STM32_I2C_CR1_OFFSET, 0, I2C_CR1_ACK);
        }

      /* Increment to next pointer and decrement message count */

      priv->msgv++;
      priv->msgc--;
    }

 /* In 10-bit addressing mode, was first byte sent */
    
  else if (status & I2C_SR1_ADD10)
    {
      /* \todo Finish 10-bit mode addressing */
    }

  /* Was address sent, continue with ether sending or reading data */
    
  else if (!(priv->flags & I2C_M_READ) && (status & (I2C_SR1_ADDR | I2C_SR1_TXE)))
    {
      if (--priv->dcnt >= 0)
        {
          /* Send a byte */

          intdbg("Send byte: %2x\n", *priv->ptr);
          stm32_i2c_putreg(priv, STM32_I2C_DR_OFFSET, *priv->ptr++); 
        }
    }

  else if ((priv->flags & I2C_M_READ) && (status & I2C_SR1_ADDR))
    {
      /* Enable RxNE and TxE buffers in order to receive one or multiple bytes */

      stm32_i2c_modifyreg(priv, STM32_I2C_CR2_OFFSET, 0, I2C_CR2_ITBUFEN);
    }

  /* More bytes to read */

  else if (status & I2C_SR1_RXNE)
    {
      /* Read a byte, if dcnt goes < 0, then read dummy bytes to ack ISRs */
    
      intdbg("dcnt=%d\n", priv->dcnt);
      if (--priv->dcnt >= 0)
        {
          *priv->ptr++ = stm32_i2c_getreg(priv, STM32_I2C_DR_OFFSET);
          intdbg("Received: %2x\n", *(priv->ptr-1) );

          /* Disable acknowledge when last byte is to be received */

          if (priv->dcnt == 1)
            {
              stm32_i2c_modifyreg(priv, STM32_I2C_CR1_OFFSET, I2C_CR1_ACK, 0);  
            }
        }
    }
    
  /* Do we have more bytes to send, enable/disable buffer interrupts
   * (these ISRs could be replaced by DMAs)
   */
     
  if (priv->dcnt>0)
    {
      stm32_i2c_modifyreg(priv, STM32_I2C_CR2_OFFSET, 0, I2C_CR2_ITBUFEN);
    }
  else if (priv->dcnt==0)
    {
      stm32_i2c_modifyreg(priv, STM32_I2C_CR2_OFFSET, I2C_CR2_ITBUFEN, 0);  
    }
    
  /* Was last byte received or sent?  */

  if (priv->dcnt<=0 && (status & I2C_SR1_BTF))
    {
      intdbg("BTF\n");
      stm32_i2c_getreg(priv, STM32_I2C_DR_OFFSET);    /* ACK ISR */

      /* Do we need to terminate or restart after this byte */
        
      /* If there are more messages to send, then we may:
       *  - continue with repeated start
       *  - or just continue sending writeable part
       *  - or we close down by sending the stop bit 
       */

      if (priv->msgc)
        {
          if (priv->msgv->flags & I2C_M_NORESTART)
            {
              priv->ptr   = priv->msgv->buffer;
              priv->dcnt  = priv->msgv->length;
              priv->flags = priv->msgv->flags;
              priv->msgv++;
              priv->msgc--;

              /* Restart this ISR! */

              stm32_i2c_modifyreg(priv, STM32_I2C_CR2_OFFSET, 0, I2C_CR2_ITBUFEN);
            }
          else
            {
              stm32_i2c_sendstart(priv);
            }
        }
      else if (priv->msgv)
        {
          intdbg("stop2: status = %8x\n", status);
          stm32_i2c_sendstop(priv);
          if (priv->isr_wait)
            {
              sem_post( &priv->sem_isr );
              priv->isr_wait = false;
            }

          /* Mark that we have stopped with this transaction */

          priv->msgv = NULL;
        }
    }
    
    /* Check for errors, in which case, stop the transfer and return 
     * Note that in master reception mode AF becomes set on last byte
     * since ACK is not returned. We should ignore this error.
     */
    
    if (status & I2C_SR1_ERRORMASK) {
        stm32_i2c_putreg(priv, STM32_I2C_SR1_OFFSET, 0);    /* clear flags */
        if (priv->isr_wait)
          {
            sem_post( &priv->sem_isr );
            priv->isr_wait = false;
          }
    }

    priv->status = status;
    return OK;
}

/* Decode ***************************************************************************/

#ifdef CONFIG_STM32_I2C1
static int stm32_i2c1_isr(int irq, void *context)
{
  return stm32_i2c_isr(&stm32_i2c1_priv);
}
#endif

#ifdef CONFIG_STM32_I2C2
static int stm32_i2c2_isr(int irq, void *context)
{
  return stm32_i2c_isr(&stm32_i2c2_priv);
}
#endif

/************************************************************************************
 * Private Initialization and Deinitialization
 ************************************************************************************/

/* Setup the I2C hardware, ready for operation with defaults */
static int stm32_i2c_init(FAR struct stm32_i2c_priv_s *priv)
{
  /* Power-up and configure GPIOs */

  switch (priv->base)
    {
#ifdef CONFIG_STM32_I2C1
      case STM32_I2C1_BASE:

        /* Enable power and reset the peripheral */

        modifyreg32(STM32_RCC_APB1ENR, 0, RCC_APB1ENR_I2C1EN);

        modifyreg32(STM32_RCC_APB1RSTR, 0, RCC_APB1RSTR_I2C1RST);
        modifyreg32(STM32_RCC_APB1RSTR, RCC_APB1RSTR_I2C1RST, 0);

        /* Configure pins */
            
        if (stm32_configgpio(GPIO_I2C1_SCL)==ERROR)
          {
            return ERROR;
          }

        if (stm32_configgpio(GPIO_I2C1_SDA)==ERROR)
          {
            stm32_unconfiggpio(GPIO_I2C1_SCL);
            return ERROR;
          }

        /* Attach ISRs */
            
        irq_attach(STM32_IRQ_I2C1EV, stm32_i2c1_isr);
        irq_attach(STM32_IRQ_I2C1ER, stm32_i2c1_isr);
        up_enable_irq(STM32_IRQ_I2C1EV);
        up_enable_irq(STM32_IRQ_I2C1ER);
        break;
#endif
      
#ifdef CONFIG_STM32_I2C2
      case STM32_I2C2_BASE:

        /* Enable power and reset the peripheral */

        modifyreg32(STM32_RCC_APB1ENR, 0, RCC_APB1ENR_I2C2EN);

        modifyreg32(STM32_RCC_APB1RSTR, 0, RCC_APB1RSTR_I2C2RST);
        modifyreg32(STM32_RCC_APB1RSTR, RCC_APB1RSTR_I2C2RST, 0);

        /* Configure pins */

        if (stm32_configgpio(GPIO_I2C2_SCL)==ERROR)
          {
            return ERROR;
          }

        if (stm32_configgpio(GPIO_I2C2_SDA)==ERROR)
          {
            stm32_unconfiggpio(GPIO_I2C2_SCL);
            return ERROR;
          }

        /* Attach ISRs */

        irq_attach(STM32_IRQ_I2C2EV, stm32_i2c2_isr);
        irq_attach(STM32_IRQ_I2C2ER, stm32_i2c2_isr);
        up_enable_irq(STM32_IRQ_I2C2EV);
        up_enable_irq(STM32_IRQ_I2C2ER);
        break;
#endif

      default:
        return ERROR;
    }

  /* Set peripheral frequency, where it must be at least 2 MHz  for 100 kHz
   * or 4 MHz for 400 kHz.  This also disables all I2C interrupts.
   */

  stm32_i2c_putreg(priv, STM32_I2C_CR2_OFFSET, (STM32_PCLK1_FREQUENCY / 1000000));
  stm32_i2c_setclock(priv, 100000);
        
  /* Enable I2C */
    
  stm32_i2c_putreg(priv, STM32_I2C_CR1_OFFSET, I2C_CR1_PE);
  return OK;
}

/* Shutdown the I2C hardware  */
static int stm32_i2c_deinit(FAR struct stm32_i2c_priv_s *priv)
{
  /* Disable I2C */

  stm32_i2c_putreg(priv, STM32_I2C_CR1_OFFSET, 0);

  switch (priv->base)
    {
#ifdef CONFIG_STM32_I2C1
      case STM32_I2C1_BASE:
        stm32_unconfiggpio(GPIO_I2C1_SCL);
        stm32_unconfiggpio(GPIO_I2C1_SDA);
                
        up_disable_irq(STM32_IRQ_I2C1EV);
        up_disable_irq(STM32_IRQ_I2C1ER);
        irq_detach(STM32_IRQ_I2C1EV);
        irq_detach(STM32_IRQ_I2C1ER);

        modifyreg32(STM32_RCC_APB1ENR, RCC_APB1ENR_I2C1EN, 0);
        break;
#endif
      
#ifdef CONFIG_STM32_I2C2
      case STM32_I2C2_BASE:
        stm32_unconfiggpio(GPIO_I2C2_SCL);
        stm32_unconfiggpio(GPIO_I2C2_SDA);

        up_disable_irq(STM32_IRQ_I2C1EV);
        up_disable_irq(STM32_IRQ_I2C1ER);
        irq_detach(STM32_IRQ_I2C1EV);
        irq_detach(STM32_IRQ_I2C1ER);

        modifyreg32(STM32_RCC_APB1ENR, RCC_APB1ENR_I2C2EN, 0);
        break;
#endif
        
      default:
        return ERROR;
    }

  return OK;
}

/************************************************************************************
 * Device Driver OPS - Blocking Type
 ************************************************************************************/

uint32_t stm32_i2c_setfrequency(FAR struct i2c_dev_s *dev, uint32_t frequency)
{
  stm32_i2c_sem_wait(dev);

#if STM32_PCLK1_FREQUENCY < 4000000
  ((struct stm32_i2c_inst_s *)dev)->frequency = 100000;
#else
  ((struct stm32_i2c_inst_s *)dev)->frequency = frequency;
#endif

  stm32_i2c_sem_post(dev);    
  return ((struct stm32_i2c_inst_s *)dev)->frequency;
}

int stm32_i2c_setaddress(FAR struct i2c_dev_s *dev, int addr, int nbits)
{
  stm32_i2c_sem_wait(dev);

  ((struct stm32_i2c_inst_s *)dev)->address = addr;
  ((struct stm32_i2c_inst_s *)dev)->flags   = (nbits == 10) ? I2C_M_TEN : 0;

    stm32_i2c_sem_post(dev);
    return OK;
}

int stm32_i2c_process(FAR struct i2c_dev_s *dev, FAR struct i2c_msg_s *msgs, int count)
{
  struct stm32_i2c_inst_s *inst = (struct stm32_i2c_inst_s *)dev;
  uint32_t    status = 0;
  uint32_t    ahbenr;
  int         status_errno = 0;

  ASSERT(count);

  /* Disable FSMC that shares a pin with I2C1 (LBAR) */

  ahbenr = stm32_i2c_disablefsmc(inst->priv);

  /* Wait as stop might still be in progress 
   * 
   * \todo GET RID OF THIS PERFORMANCE LOSS and for() loop
   */
 
  for (; stm32_i2c_getreg(inst->priv, STM32_I2C_CR1_OFFSET) & I2C_CR1_STOP; )
    {
      up_waste();
    }
    
  /* Old transfers are done */

  inst->priv->msgv = msgs;
  inst->priv->msgc = count;
        
  /* Set I2C clock frequency (on change it toggles I2C_CR1_PE !) */

  stm32_i2c_setclock(inst->priv, inst->frequency);

  /* Clear any pending error interrupts */

  stm32_i2c_putreg(inst->priv, STM32_I2C_SR1_OFFSET, 0);

  /* Trigger start condition, then the process moves into the ISR.  I2C
   * interrupts will be enabled within stm32_i2c_waitisr().
   */

  stm32_i2c_sendstart(inst->priv);

  /* Wait for an ISR, if there was a timeout, fetch latest status to get
   * the BUSY flag.
   */

  if (stm32_i2c_sem_waitisr(dev) == ERROR)
    {
      status = stm32_i2c_getstatus(inst->priv);
      status_errno = ETIMEDOUT;

      /* " Note: When the STOP, START or PEC bit is set, the software must
       *   not perform any write access to I2C_CR1 before this bit is
       *   cleared by hardware. Otherwise there is a risk of setting a
       *   second STOP, START or PEC request."
       */

      stm32_i2c_clrstart(inst->priv);
    }
  else
    {
      /* clear SR2 (BUSY flag) as we've done successfully */

      status = inst->priv->status & 0xffff;
    }

  /* Check for error status conditions */

  if (status & I2C_SR1_BERR)
    {
      /* Bus Error */

      status_errno = EIO;
    }
  else if (status & I2C_SR1_ARLO)
    {
      /* Arbitration Lost (master mode) */

      status_errno = EAGAIN;
    }
  else if (status & I2C_SR1_AF)
    {
      /* Acknowledge Failure */

      status_errno = ENXIO;
    }
  else if (status & I2C_SR1_OVR)
    {
      /* Overrun/Underrun */

      status_errno = EIO;
    }
  else if (status & I2C_SR1_PECERR)
    {
      /* PEC Error in reception */

      status_errno = EPROTO;
    }
  else if (status & I2C_SR1_TIMEOUT)
    {
      /* Timeout or Tlow Error */

      status_errno = ETIME;
    }
  else if (status & (I2C_SR2_BUSY << 16))
    {
      /* I2C Bus is for some reason busy */

      status_errno = EBUSY;
    }

  /* Re-enable the FSMC */

  stm32_i2c_enablefsmc(ahbenr);
  stm32_i2c_sem_post(dev);

  errno = status_errno;
  return -status_errno;
}

int stm32_i2c_write(FAR struct i2c_dev_s *dev, const uint8_t *buffer, int buflen)
{
  stm32_i2c_sem_wait(dev);   /* ensure that address or flags don't change meanwhile */

  struct i2c_msg_s msgv =
  {
    .addr   = ((struct stm32_i2c_inst_s *)dev)->address,
    .flags  = ((struct stm32_i2c_inst_s *)dev)->flags,
    .buffer = (uint8_t *)buffer,
    .length = buflen
  };
    
  return stm32_i2c_process(dev, &msgv, 1);
}

int stm32_i2c_read(FAR struct i2c_dev_s *dev, uint8_t *buffer, int buflen)
{
  stm32_i2c_sem_wait(dev);   /* ensure that address or flags don't change meanwhile */

  struct i2c_msg_s msgv =
  {
    .addr   = ((struct stm32_i2c_inst_s *)dev)->address,
    .flags  = ((struct stm32_i2c_inst_s *)dev)->flags | I2C_M_READ,
    .buffer = buffer,
    .length = buflen
  };
    
  return stm32_i2c_process(dev, &msgv, 1);
}

#ifdef CONFIG_I2C_WRITEREAD
int stm32_i2c_writeread(FAR struct i2c_dev_s *dev, const uint8_t *wbuffer, int wbuflen,
                        uint8_t *buffer, int buflen)
{
  stm32_i2c_sem_wait(dev);   /* ensure that address or flags don't change meanwhile */

  struct i2c_msg_s msgv[2] =
  {
    {
      .addr   = ((struct stm32_i2c_inst_s *)dev)->address,
      .flags  = ((struct stm32_i2c_inst_s *)dev)->flags,
      .buffer = (uint8_t *)wbuffer,          /* this is really ugly, sorry const ... */
      .length = wbuflen
    },
    {
      .addr   = ((struct stm32_i2c_inst_s *)dev)->address,
      .flags  = ((struct stm32_i2c_inst_s *)dev)->flags | ((buflen>0) ? I2C_M_READ : I2C_M_NORESTART),
      .buffer = buffer,
      .length = (buflen>0) ? buflen : -buflen
    }
  };

  return stm32_i2c_process(dev, msgv, 2);
}
#endif

#ifdef CONFIG_I2C_TRANSFER
int stm32_i2c_transfer(FAR struct i2c_dev_s *dev, FAR struct i2c_msg_s *msgs, int count)
{
  stm32_i2c_sem_wait(dev);   /* ensure that address or flags don't change meanwhile */
  return stm32_i2c_process(dev, msgs, count);
}
#endif

/************************************************************************************
 * Device Structures, Instantiation
 ************************************************************************************/

struct i2c_ops_s stm32_i2c_ops =
{
  .setfrequency       = stm32_i2c_setfrequency,
  .setaddress         = stm32_i2c_setaddress,
  .write              = stm32_i2c_write,
  .read               = stm32_i2c_read
#ifdef CONFIG_I2C_WRITEREAD
  , .writeread          = stm32_i2c_writeread
#endif
#ifdef CONFIG_I2C_TRANSFER
  , .transfer           = stm32_i2c_transfer
#endif
#ifdef CONFIG_I2C_SLAVE
  , .setownaddress      = stm32_i2c_setownaddress,
    .registercallback   = stm32_i2c_registercallback
#endif
};

/************************************************************************************
 * Public Function - Initialization
 ************************************************************************************/

FAR struct i2c_dev_s * up_i2cinitialize(int port)
{
  struct stm32_i2c_priv_s * priv = NULL;  /* private data of device with multiple instances */
  struct stm32_i2c_inst_s * inst = NULL;  /* device, single instance */
  int irqs;

#if STM32_PCLK1_FREQUENCY < 4000000
#   warning STM32_I2C_INIT: Peripheral clock must be at least 4 MHz to support 400 kHz operation.
#endif

#if STM32_PCLK1_FREQUENCY < 2000000
#   warning STM32_I2C_INIT: Peripheral clock must be at least 2 MHz to support 100 kHz operation.
    return NULL;
#endif
    
  /* Get I2C private structure */

  switch (port)
    {
#ifdef CONFIG_STM32_I2C1
      case 1:
        priv = (struct stm32_i2c_priv_s *)&stm32_i2c1_priv;
        break;
#endif
#ifdef CONFIG_STM32_I2C2
      case 2:
        priv = (struct stm32_i2c_priv_s *)&stm32_i2c2_priv;
        break;
#endif
      default:
        return NULL;
    }

  /* Allocate instance */
    
  if (!(inst = kmalloc( sizeof(struct stm32_i2c_inst_s))))
    {
      return NULL;
    }

  /* Initialize instance */

  inst->ops       = &stm32_i2c_ops;
  inst->priv      = priv;
  inst->frequency = 100000;
  inst->address   = 0;
  inst->flags     = 0;

  /* Init private data for the first time, increment refs count,
   * power-up hardware and configure GPIOs. 
   */
    
  irqs = irqsave();
    
  if ((volatile int)priv->refs++ == 0)
    {
      stm32_i2c_sem_init( (struct i2c_dev_s *)inst );
      stm32_i2c_init( priv );
    }
    
  irqrestore(irqs);
  return (struct i2c_dev_s *)inst;
}

int up_i2cuninitialize(FAR struct i2c_dev_s * dev)
{
  int irqs;
    
  ASSERT(dev);
    
  /* Decrement refs and check for underflow */
    
  if (((struct stm32_i2c_inst_s *)dev)->priv->refs == 0) 
    {
      return ERROR;
    }

  irqs = irqsave();

  if (--((struct stm32_i2c_inst_s *)dev)->priv->refs)
    {
      irqrestore(irqs);
      kfree(dev);
      return OK;
    }

  irqrestore(irqs);

  /* Disable power and other HW resource (GPIO's) */

  stm32_i2c_deinit( ((struct stm32_i2c_inst_s *)dev)->priv );

  /* Release unused resources */

  stm32_i2c_sem_destroy( (struct i2c_dev_s *)dev );

  kfree(dev);
  return OK;
}

#endif /* defined(CONFIG_STM32_I2C1) && defined(CONFIG_STM32_I2C2) */