i2c.c

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/*
 * Copyright (C) 2010 Bluecherry, LLC www.bluecherrydvr.com
 * Copyright (C) 2010 Ben Collins <[email protected]>
 *
 * 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 program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* XXX: The SOLO6x10 i2c does not have separate interrupts for each i2c
 * channel. The bus can only handle one i2c event at a time. The below handles
 * this all wrong. We should be using the status registers to see if the bus
 * is in use, and have a global lock to check the status register. Also,
 * the bulk of the work should be handled out-of-interrupt. The ugly loops
 * that occur during interrupt scare me. The ISR should merely signal
 * thread context, ACK the interrupt, and move on. -- BenC */

#include <linux/kernel.h>
#include "solo6x10.h"

u8 solo_i2c_readbyte(struct solo_dev *solo_dev, int id, u8 addr, u8 off)
{
    struct i2c_msg msgs[2];
    u8 data;

    msgs[0].flags = 0;
    msgs[0].addr = addr;
    msgs[0].len = 1;
    msgs[0].buf = &off;

    msgs[1].flags = I2C_M_RD;
    msgs[1].addr = addr;
    msgs[1].len = 1;
    msgs[1].buf = &data;

    i2c_transfer(&solo_dev->i2c_adap[id], msgs, 2);

    return data;
}

void solo_i2c_writebyte(struct solo_dev *solo_dev, int id, u8 addr,
            u8 off, u8 data)
{
    struct i2c_msg msgs;
    u8 buf[2];

    buf[0] = off;
    buf[1] = data;
    msgs.flags = 0;
    msgs.addr = addr;
    msgs.len = 2;
    msgs.buf = buf;

    i2c_transfer(&solo_dev->i2c_adap[id], &msgs, 1);
}

static void solo_i2c_flush(struct solo_dev *solo_dev, int wr)
{
    u32 ctrl;

    ctrl = SOLO_IIC_CH_SET(solo_dev->i2c_id);

    if (solo_dev->i2c_state == IIC_STATE_START)
        ctrl |= SOLO_IIC_START;

    if (wr) {
        ctrl |= SOLO_IIC_WRITE;
    } else {
        ctrl |= SOLO_IIC_READ;
        if (!(solo_dev->i2c_msg->flags & I2C_M_NO_RD_ACK))
            ctrl |= SOLO_IIC_ACK_EN;
    }

    if (solo_dev->i2c_msg_ptr == solo_dev->i2c_msg->len)
        ctrl |= SOLO_IIC_STOP;

    solo_reg_write(solo_dev, SOLO_IIC_CTRL, ctrl);
}

static void solo_i2c_start(struct solo_dev *solo_dev)
{
    u32 addr = solo_dev->i2c_msg->addr << 1;

    if (solo_dev->i2c_msg->flags & I2C_M_RD)
        addr |= 1;

    solo_dev->i2c_state = IIC_STATE_START;
    solo_reg_write(solo_dev, SOLO_IIC_TXD, addr);
    solo_i2c_flush(solo_dev, 1);
}

static void solo_i2c_stop(struct solo_dev *solo_dev)
{
    solo_irq_off(solo_dev, SOLO_IRQ_IIC);
    solo_reg_write(solo_dev, SOLO_IIC_CTRL, 0);
    solo_dev->i2c_state = IIC_STATE_STOP;
    wake_up(&solo_dev->i2c_wait);
}

static int solo_i2c_handle_read(struct solo_dev *solo_dev)
{
prepare_read:
    if (solo_dev->i2c_msg_ptr != solo_dev->i2c_msg->len) {
        solo_i2c_flush(solo_dev, 0);
        return 0;
    }

    solo_dev->i2c_msg_ptr = 0;
    solo_dev->i2c_msg++;
    solo_dev->i2c_msg_num--;

    if (solo_dev->i2c_msg_num == 0) {
        solo_i2c_stop(solo_dev);
        return 0;
    }

    if (!(solo_dev->i2c_msg->flags & I2C_M_NOSTART)) {
        solo_i2c_start(solo_dev);
    } else {
        if (solo_dev->i2c_msg->flags & I2C_M_RD)
            goto prepare_read;
        else
            solo_i2c_stop(solo_dev);
    }

    return 0;
}

static int solo_i2c_handle_write(struct solo_dev *solo_dev)
{
retry_write:
    if (solo_dev->i2c_msg_ptr != solo_dev->i2c_msg->len) {
        solo_reg_write(solo_dev, SOLO_IIC_TXD,
                   solo_dev->i2c_msg->buf[solo_dev->i2c_msg_ptr]);
        solo_dev->i2c_msg_ptr++;
        solo_i2c_flush(solo_dev, 1);
        return 0;
    }

    solo_dev->i2c_msg_ptr = 0;
    solo_dev->i2c_msg++;
    solo_dev->i2c_msg_num--;

    if (solo_dev->i2c_msg_num == 0) {
        solo_i2c_stop(solo_dev);
        return 0;
    }

    if (!(solo_dev->i2c_msg->flags & I2C_M_NOSTART)) {
        solo_i2c_start(solo_dev);
    } else {
        if (solo_dev->i2c_msg->flags & I2C_M_RD)
            solo_i2c_stop(solo_dev);
        else
            goto retry_write;
    }

    return 0;
}

int solo_i2c_isr(struct solo_dev *solo_dev)
{
    u32 status = solo_reg_read(solo_dev, SOLO_IIC_CTRL);
    int ret = -EINVAL;

    solo_reg_write(solo_dev, SOLO_IRQ_STAT, SOLO_IRQ_IIC);

    if (status & (SOLO_IIC_STATE_TRNS | SOLO_IIC_STATE_SIG_ERR) ||
        solo_dev->i2c_id < 0) {
        solo_i2c_stop(solo_dev);
        return -ENXIO;
    }

    switch (solo_dev->i2c_state) {
    case IIC_STATE_START:
        if (solo_dev->i2c_msg->flags & I2C_M_RD) {
            solo_dev->i2c_state = IIC_STATE_READ;
            ret = solo_i2c_handle_read(solo_dev);
            break;
        }

        solo_dev->i2c_state = IIC_STATE_WRITE;
    case IIC_STATE_WRITE:
        ret = solo_i2c_handle_write(solo_dev);
        break;

    case IIC_STATE_READ:
        solo_dev->i2c_msg->buf[solo_dev->i2c_msg_ptr] =
            solo_reg_read(solo_dev, SOLO_IIC_RXD);
        solo_dev->i2c_msg_ptr++;

        ret = solo_i2c_handle_read(solo_dev);
        break;

    default:
        solo_i2c_stop(solo_dev);
    }

    return ret;
}

static int solo_i2c_master_xfer(struct i2c_adapter *adap,
                struct i2c_msg msgs[], int num)
{
    struct solo_dev *solo_dev = adap->algo_data;
    unsigned long timeout;
    int ret;
    int i;
    DEFINE_WAIT(wait);

    for (i = 0; i < SOLO_I2C_ADAPTERS; i++) {
        if (&solo_dev->i2c_adap[i] == adap)
            break;
    }

    if (i == SOLO_I2C_ADAPTERS)
        return num; /* XXX Right return value for failure? */

    mutex_lock(&solo_dev->i2c_mutex);
    solo_dev->i2c_id = i;
    solo_dev->i2c_msg = msgs;
    solo_dev->i2c_msg_num = num;
    solo_dev->i2c_msg_ptr = 0;

    solo_reg_write(solo_dev, SOLO_IIC_CTRL, 0);
    solo_irq_on(solo_dev, SOLO_IRQ_IIC);
    solo_i2c_start(solo_dev);

    timeout = HZ / 2;

    for (;;) {
        prepare_to_wait(&solo_dev->i2c_wait, &wait, TASK_INTERRUPTIBLE);

        if (solo_dev->i2c_state == IIC_STATE_STOP)
            break;

        timeout = schedule_timeout(timeout);
        if (!timeout)
            break;

        if (signal_pending(current))
            break;
    }

    finish_wait(&solo_dev->i2c_wait, &wait);
    ret = num - solo_dev->i2c_msg_num;
    solo_dev->i2c_state = IIC_STATE_IDLE;
    solo_dev->i2c_id = -1;

    mutex_unlock(&solo_dev->i2c_mutex);

    return ret;
}

static u32 solo_i2c_functionality(struct i2c_adapter *adap)
{
    return I2C_FUNC_I2C;
}

static struct i2c_algorithm solo_i2c_algo = {
    .master_xfer    = solo_i2c_master_xfer,
    .functionality  = solo_i2c_functionality,
};

int solo_i2c_init(struct solo_dev *solo_dev)
{
    int i;
    int ret;

    solo_reg_write(solo_dev, SOLO_IIC_CFG,
               SOLO_IIC_PRESCALE(8) | SOLO_IIC_ENABLE);

    solo_dev->i2c_id = -1;
    solo_dev->i2c_state = IIC_STATE_IDLE;
    init_waitqueue_head(&solo_dev->i2c_wait);
    mutex_init(&solo_dev->i2c_mutex);

    for (i = 0; i < SOLO_I2C_ADAPTERS; i++) {
        struct i2c_adapter *adap = &solo_dev->i2c_adap[i];

        snprintf(adap->name, I2C_NAME_SIZE, "%s I2C %d", SOLO6X10_NAME, i);
        adap->algo = &solo_i2c_algo;
        adap->algo_data = solo_dev;
        adap->retries = 1;
        adap->dev.parent = &solo_dev->pdev->dev;

        ret = i2c_add_adapter(adap);
        if (ret) {
            adap->algo_data = NULL;
            break;
        }
    }

    if (ret) {
        for (i = 0; i < SOLO_I2C_ADAPTERS; i++) {
            if (!solo_dev->i2c_adap[i].algo_data)
                break;
            i2c_del_adapter(&solo_dev->i2c_adap[i]);
            solo_dev->i2c_adap[i].algo_data = NULL;
        }
        return ret;
    }

    dev_info(&solo_dev->pdev->dev, "Enabled %d i2c adapters\n",
         SOLO_I2C_ADAPTERS);

    return 0;
}

void solo_i2c_exit(struct solo_dev *solo_dev)
{
    int i;

    for (i = 0; i < SOLO_I2C_ADAPTERS; i++) {
        if (!solo_dev->i2c_adap[i].algo_data)
            continue;
        i2c_del_adapter(&solo_dev->i2c_adap[i]);
        solo_dev->i2c_adap[i].algo_data = NULL;
    }
}