DDC/I2C/SMBus overhaul (incomplete, commit for the night)
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RichardG867
277
src/device/i2c_gpio.c
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277
src/device/i2c_gpio.c
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/*
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* 86Box A hypervisor and IBM PC system emulator that specializes in
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* running old operating systems and software designed for IBM
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* PC systems and compatibles from 1981 through fairly recent
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* system designs based on the PCI bus.
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*
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* This file is part of the 86Box distribution.
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*
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* Implementation of a GPIO-based I2C device.
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*
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*
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*
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* Authors: Sarah Walker, <http://pcem-emulator.co.uk/>
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* RichardG, <richardg867@gmail.com>
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*
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* Copyright 2008-2020 Sarah Walker.
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* Copyright 2020 RichardG.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <wchar.h>
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#include <math.h>
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#include <86box/86box.h>
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#include <86box/i2c.h>
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enum {
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TRANSMITTER_SLAVE = 1,
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TRANSMITTER_MASTER = 2
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};
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enum {
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I2C_IDLE = 0,
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I2C_RECEIVE,
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I2C_RECEIVE_WAIT,
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I2C_TRANSMIT_START,
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I2C_TRANSMIT,
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I2C_ACKNOWLEDGE,
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I2C_TRANSACKNOWLEDGE,
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I2C_TRANSMIT_WAIT
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};
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enum {
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SLAVE_IDLE = 0,
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SLAVE_RECEIVEADDR,
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SLAVE_RECEIVEDATA,
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SLAVE_SENDDATA,
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SLAVE_INVALID
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};
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typedef struct {
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void *i2c;
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uint8_t scl, sda, state, slave_state, slave_addr, slave_reg,
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slave_writing, slave_rw, last_sda, pos, transmit, byte;
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} i2c_gpio_t;
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void *
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i2c_gpio_init(char *bus_name)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) malloc(sizeof(i2c_gpio_t));
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memset(dev, 0, sizeof(i2c_gpio_t));
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dev->i2c = i2c_addbus(bus_name);
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dev->scl = dev->sda = 1;
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return dev;
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}
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void
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i2c_gpio_close(void *dev_handle)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) dev_handle;
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i2c_removebus(dev->i2c);
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free(dev);
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}
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void
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i2c_gpio_next_byte(i2c_gpio_t *dev)
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{
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dev->byte = i2c_read_byte(dev->i2c, dev->slave_addr);
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}
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void
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i2c_gpio_write(i2c_gpio_t *dev)
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{
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switch (dev->slave_state) {
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case SLAVE_IDLE:
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dev->slave_addr = dev->byte >> 1;
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if (!i2c_has_device(dev->i2c, dev->slave_addr)) {
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dev->slave_state = SLAVE_INVALID;
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break;
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}
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dev->slave_rw = dev->byte & 1;
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dev->slave_writing = 0;
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if (dev->slave_rw) {
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dev->slave_state = SLAVE_SENDDATA;
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dev->transmit = TRANSMITTER_SLAVE;
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dev->byte = i2c_read_byte(dev->i2c, dev->slave_addr);
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} else {
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dev->slave_state = SLAVE_RECEIVEADDR;
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dev->transmit = TRANSMITTER_MASTER;
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}
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pclog("slave_idle %02X %d\n", dev->slave_addr, dev->slave_rw);
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break;
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case SLAVE_RECEIVEADDR:
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pclog("slave_receiveaddr %02X %d\n", dev->slave_addr, dev->slave_rw);
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i2c_write_byte(dev->i2c, dev->slave_addr, dev->byte);
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dev->slave_writing = 1;
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dev->slave_reg = dev->byte;
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dev->slave_state = dev->slave_rw ? SLAVE_SENDDATA : SLAVE_RECEIVEDATA;
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break;
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case SLAVE_RECEIVEDATA:
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pclog("slave_receivedata %02X %d = %02X\n", dev->slave_addr, dev->slave_rw, dev->byte);
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dev->slave_writing = 0;
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i2c_write_byte_cmd(dev->i2c, dev->slave_addr, dev->slave_reg, dev->byte);
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break;
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case SLAVE_SENDDATA:
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pclog("slave_senddata %02X %d = %02X\n", dev->slave_addr, dev->slave_rw, dev->byte);
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break;
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}
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}
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void
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i2c_gpio_stop(i2c_gpio_t *dev)
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{
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pclog("stopping... state = %d\n", dev->slave_state);
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if (dev->slave_writing)
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i2c_write_byte(dev->i2c, dev->slave_addr, dev->slave_reg);
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dev->slave_state = SLAVE_IDLE;
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dev->transmit = TRANSMITTER_MASTER;
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}
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void
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i2c_gpio_set(void *dev_handle, uint8_t scl, uint8_t sda)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) dev_handle;
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switch (dev->state) {
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case I2C_IDLE:
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if (dev->scl && scl && dev->last_sda && !sda) { /* start bit */
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dev->state = I2C_RECEIVE;
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dev->pos = 0;
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}
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break;
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case I2C_RECEIVE_WAIT:
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if (!dev->scl && scl)
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dev->state = I2C_RECEIVE;
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/* fall-through */
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case I2C_RECEIVE:
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if (!dev->scl && scl) {
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dev->byte <<= 1;
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if (sda)
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dev->byte |= 1;
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else
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dev->byte &= 0xfe;
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if (++dev->pos == 8) {
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i2c_gpio_write(dev);
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dev->state = I2C_ACKNOWLEDGE;
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}
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} else if (dev->scl && scl) {
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if (sda && !dev->last_sda) { /* stop bit */
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dev->state = I2C_IDLE;
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i2c_gpio_stop(dev);
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} else if (!sda && dev->last_sda) { /* start bit */
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dev->pos = 0;
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dev->slave_state = SLAVE_IDLE;
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}
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}
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break;
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case I2C_ACKNOWLEDGE:
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if (!dev->scl && scl) {
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sda = 0;
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dev->pos = 0;
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dev->state = (dev->transmit == TRANSMITTER_MASTER) ? I2C_RECEIVE_WAIT : I2C_TRANSMIT;
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}
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break;
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case I2C_TRANSACKNOWLEDGE:
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if (!dev->scl && scl) {
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if (sda) { /* not acknowledged; must be end of transfer */
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dev->state = I2C_IDLE;
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i2c_gpio_stop(dev);
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} else { /* next byte to transfer */
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dev->state = I2C_TRANSMIT_START;
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i2c_gpio_next_byte(dev);
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dev->pos = 0;
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}
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}
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break;
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case I2C_TRANSMIT_WAIT:
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if (dev->scl && scl) {
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if (dev->last_sda && !sda) { /* start bit */
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i2c_gpio_next_byte(dev);
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dev->pos = 0;
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}
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if (!dev->last_sda && sda) { /* stop bit */
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dev->state = I2C_IDLE;
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i2c_gpio_stop(dev);
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}
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}
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break;
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case I2C_TRANSMIT_START:
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if (!dev->scl && scl)
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dev->state = I2C_TRANSMIT;
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if (dev->scl && scl && !dev->last_sda && sda) { /* stop bit */
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dev->state = I2C_IDLE;
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i2c_gpio_stop(dev);
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}
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/* fall-through */
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case I2C_TRANSMIT:
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if (!dev->scl && scl) {
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dev->scl = scl;
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dev->sda = sda = dev->byte & 0x80;
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dev->byte <<= 1;
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dev->pos++;
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return;
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}
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if (dev->scl && !scl && (dev->pos == 8))
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dev->state = I2C_TRANSACKNOWLEDGE;
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break;
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}
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if (!dev->scl && scl)
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dev->sda = sda;
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dev->last_sda = sda;
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dev->scl = scl;
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}
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uint8_t
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i2c_gpio_get_scl(void *dev_handle)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) dev_handle;
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return dev->scl;
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}
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uint8_t
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i2c_gpio_get_sda(void *dev_handle)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) dev_handle;
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if ((dev->state == I2C_TRANSMIT) || (dev->state == I2C_ACKNOWLEDGE))
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return dev->sda;
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else if (dev->state == I2C_RECEIVE_WAIT)
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return 0; /* ack */
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else
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return 1;
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}
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void *
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i2c_gpio_get_bus(void *dev_handle)
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{
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i2c_gpio_t *dev = (i2c_gpio_t *) dev_handle;
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return dev->i2c;
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}
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