rockbox/firmware/target/arm/rk27xx/i2c-rk27xx.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2011 by Marcin Bukat
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/

#include "config.h"
#include "system.h"
#include "kernel.h"
#include "i2c-rk27xx.h"

/* NOT TESTED YET */

/*  Driver for the rockchip rk27xx built-in I2C controller in master mode
    
    Both the i2c_read and i2c_write function take the following arguments:
    * slave, the address of the i2c slave device to read from / write to
    * address, optional sub-address in the i2c slave (unused if -1)
    * len, number of bytes to be transfered
    * data, pointer to data to be transfered
    A return value other than 0 indicates an error.
*/

static struct mutex i2c_mtx;

static bool i2c_write_byte(uint8_t data, bool start)
{
   long timeout = current_tick + HZ / 50;

   /* START */
   I2C_CONR |= (1<<3)  | (1<<2); /* master port enable, transmit bit */
   I2C_MTXR = data;

   if (start)
       I2C_LCMR = (1<<2) | (1<<0); /* resume op, start bit */
   else
       I2C_LCMR = (1<<2); /* resume op */

   I2C_CONR &= ~(1<<4); /* ACK enable */

   /* wait for ACK from slave */
   while ( !(I2C_ISR & (1<<0)) || (I2C_LSR & (1<<0)) )
       if (TIME_AFTER(current_tick, timeout))
           return false;

   /* clear status bit */
   I2C_ISR &= ~(1<<0);

   return true;
}

static bool i2c_read_byte(unsigned char *data)
{
   long timeout = current_tick + HZ / 50;

   I2C_LCMR = (1<<2); /* resume op */

   while (I2C_ISR & (1<<1))
       if (TIME_AFTER(current_tick, timeout))
           return false;

   *data = I2C_MRXR;

   /* clear status bit */
   I2C_ISR &= ~(1<<1);

  return true;
}

static bool i2c_stop(void)
{
   long timeout = current_tick + HZ / 50;

   I2C_CONR &= ~(1<<4);
   I2C_LCMR |= (1<<2) | (1<<1); /* resume op, stop */

   while (I2C_LCMR & (1<<1))
       if (TIME_AFTER(current_tick, timeout))
           return false;

   return true;
}

/* route i2c bus to internal codec or external bus
 * internal codec has 0x27 i2c slave address so
 * access to this address is routed to internal bus.
 * All other addresses are routed to external pads
 */
static void i2c_iomux(unsigned char slave)
{
   unsigned long muxa = SCU_IOMUXA_CON & ~(0x1f<<14);

   if (slave == (0x27<<1))
   {
       /* internal codec */
       SCU_IOMUXA_CON = muxa | (1<<16) | (1<<14);
   }
   else
   {
       /* external I2C bus */
       SCU_IOMUXA_CON = muxa | (1<<18);
   }
}

void i2c_init(void)
{
   mutex_init(&i2c_mtx);

   SCU_CLKCFG &= ~(1<< 20);

   I2C_OPR |= (1<<7); /* reset state machine */
   sleep(HZ/100);
   I2C_OPR &= ~((1<<7) | (1<<6)); /* clear ENABLE bit, deasert reset */

   /* set I2C divider to stay within allowed SCL freq limit
    * APBfreq = 50Mhz
    * SCLfreq = (APBfreq/5*(I2CCDVR[5:3] + 1) * 2^((I2CCDVR[2:0] + 1))
    */
   I2C_OPR = (I2C_OPR & ~(0x3F)) | (6<<3) | 1<<0;

   I2C_IER = 0x00;

   I2C_OPR |= (1<<6); /* enable i2c core */
}

int i2c_write(unsigned char slave, int address, int len,
              const unsigned char *data)
{
   mutex_lock(&i2c_mtx);

   i2c_iomux(slave);

   /* START */
   if (! i2c_write_byte(slave & ~1, true))
   {
       mutex_unlock(&i2c_mtx);
       return 1;
   }

   if (address >= 0)
   {
       if (! i2c_write_byte(address, false))
       {
           mutex_unlock(&i2c_mtx);
           return 2;
       }
   }

   /* write data */
   while (len--)
   {
       if (! i2c_write_byte(*data++, false))
       {
           mutex_unlock(&i2c_mtx);
           return 4;
       }
   }

   /* STOP */
   if (! i2c_stop())
   {
       mutex_unlock(&i2c_mtx);
       return 5;
   }

   mutex_unlock(&i2c_mtx);
   return 0;
}

int i2c_read(unsigned char slave, int address, int len, unsigned char *data)
{
   mutex_lock(&i2c_mtx);

   i2c_iomux(slave);

   if (address >= 0)
   {
       /* START */
       if (! i2c_write_byte(slave & ~1, true))
       {
           mutex_unlock(&i2c_mtx);
           return 1;
       }

       /* write address */
       if (! i2c_write_byte(address, false))
       {
           mutex_unlock(&i2c_mtx);
           return 2;
       }
   }

   /* (repeated) START */
   if (! i2c_write_byte(slave | 1, true))
   {
       mutex_unlock(&i2c_mtx);
       return 3;
   }

   I2C_CONR &= ~(1<<3); /* clear transmit bit (switch to receive mode) */

   while (len)
   {
       if (! i2c_read_byte(data++))
       {
               mutex_unlock(&i2c_mtx);
               return 4;
       }

       if (len == 1)
           I2C_CONR |= (1<<4); /* NACK */
       else
           I2C_CONR &= ~(1<<4); /* ACK */

       len--;
   }

   /* STOP */
   if (! i2c_stop())
   {
       mutex_unlock(&i2c_mtx);
       return 5;
   }

   mutex_unlock(&i2c_mtx);
   return 0;
}