i2c.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <device/mmio.h>
#include <assert.h>
#include <console/console.h>
#include <delay.h>
#include <device/i2c_simple.h>
#include <soc/clk.h>
#include <soc/i2c.h>
#include <soc/periph.h>
#include <timer.h>
 
#define I2C_TIMEOUT_US (1000 * USECS_PER_MSEC)
 
struct __packed i2c_regs
{
        uint8_t con;
        uint8_t _1[3];
        uint8_t stat;
        uint8_t _2[3];
        uint8_t add;
        uint8_t _3[3];
        uint8_t ds;
        uint8_t _4[3];
        uint8_t lc;
        uint8_t _5[3];
};
 
struct s3c24x0_i2c_bus {
        int bus_num;
        struct i2c_regs *regs;
        enum periph_id periph_id;
};
 
enum {
        I2cConIntPending = 0x1 << 4,
        I2cConIntEn = 0x1 << 5,
        I2cConAckGen = 0x1 << 7
};
 
enum {
        I2cStatAck = 0x1 << 0,
        I2cStatAddrZero = 0x1 << 1,
        I2cStatAddrSlave = 0x1 << 2,
        I2cStatArb = 0x1 << 3,
        I2cStatEnable = 0x1 << 4,
        I2cStatStartStop = 0x1 << 5,
        I2cStatBusy = 0x1 << 5,
 
        I2cStatModeMask = 0x3 << 6,
        I2cStatSlaveRecv = 0x0 << 6,
        I2cStatSlaveXmit = 0x1 << 6,
        I2cStatMasterRecv = 0x2 << 6,
        I2cStatMasterXmit = 0x3 << 6
};
 
static struct s3c24x0_i2c_bus i2c_busses[] = {
        {
                .bus_num = 0,
                .regs = (void *)0x12c60000,
                .periph_id = PERIPH_ID_I2C0,
        },
        {
                .bus_num = 1,
                .regs = (void *)0x12c70000,
                .periph_id = PERIPH_ID_I2C1,
        },
        {
                .bus_num = 2,
                .regs = (void *)0x12c80000,
                .periph_id = PERIPH_ID_I2C2,
        },
        {
                .bus_num = 3,
                .regs = (void *)0x12c90000,
                .periph_id = PERIPH_ID_I2C3,
        },
        {
                .bus_num = 4,
                .regs = (void *)0x12ca0000,
                .periph_id = PERIPH_ID_I2C4,
        },
        {
                .bus_num = 5,
                .regs = (void *)0x12cb0000,
                .periph_id = PERIPH_ID_I2C5,
        },
        {
                .bus_num = 6,
                .regs = (void *)0x12cc0000,
                .periph_id = PERIPH_ID_I2C6,
        },
        {
                .bus_num = 7,
                .regs = (void *)0x12cd0000,
                .periph_id = PERIPH_ID_I2C7,
        },
};
 
static int i2c_int_pending(struct i2c_regs *regs)
{
        return read8(&regs->con) & I2cConIntPending;
}
 
static void i2c_clear_int(struct i2c_regs *regs)
{
        write8(&regs->con, read8(&regs->con) & ~I2cConIntPending);
}
 
static void i2c_ack_enable(struct i2c_regs *regs)
{
        write8(&regs->con, read8(&regs->con) | I2cConAckGen);
}
 
static void i2c_ack_disable(struct i2c_regs *regs)
{
        write8(&regs->con, read8(&regs->con) & ~I2cConAckGen);
}
 
static int i2c_got_ack(struct i2c_regs *regs)
{
        return !(read8(&regs->stat) & I2cStatAck);
}
 
static int i2c_wait_for_idle(struct i2c_regs *regs, int timeout_us)
{
        int timeout = DIV_ROUND_UP(timeout_us, 10);
        while (timeout--) {
                if (!(read8(&regs->stat) & I2cStatBusy))
                        return 0;
                udelay(10);
        }
        printk(BIOS_ERR, "I2C timeout waiting for idle.\n");
        return 1;
}
 
static int i2c_wait_for_int(struct i2c_regs *regs, int timeout_us)
{
        int timeout = DIV_ROUND_UP(timeout_us, 10);
        while (timeout--) {
                if (i2c_int_pending(regs))
                        return 0;
                udelay(10);
        }
        printk(BIOS_ERR, "I2C timeout waiting for I2C interrupt.\n");
        return 1;
}
 
static int i2c_send_stop(struct i2c_regs *regs)
{
        uint8_t mode = read8(&regs->stat) & (I2cStatModeMask);
        write8(&regs->stat, mode | I2cStatEnable);
        i2c_clear_int(regs);
        return i2c_wait_for_idle(regs, I2C_TIMEOUT_US);
}
 
static int i2c_send_start(struct i2c_regs *regs, int read, int chip)
{
        write8(&regs->ds, chip << 1);
        uint8_t mode = read ? I2cStatMasterRecv : I2cStatMasterXmit;
        write8(&regs->stat, mode | I2cStatStartStop | I2cStatEnable);
        i2c_clear_int(regs);
 
        if (i2c_wait_for_int(regs, I2C_TIMEOUT_US))
                return 1;
 
        if (!i2c_got_ack(regs)) {
                // Nobody home, but they may just be asleep.
                return 1;
        }
 
        return 0;
}
 
static int i2c_xmit_buf(struct i2c_regs *regs, uint8_t *data, int len)
{
        ASSERT(len);
 
        i2c_ack_enable(regs);
 
        int i;
        for (i = 0; i < len; i++) {
                write8(&regs->ds, data[i]);
 
                i2c_clear_int(regs);
                if (i2c_wait_for_int(regs, CONFIG_I2C_TRANSFER_TIMEOUT_US))
                        return 1;
 
                if (!i2c_got_ack(regs)) {
                        printk(BIOS_INFO, "I2c nacked.\n");
                        return 1;
                }
        }
 
        return 0;
}
 
static int i2c_recv_buf(struct i2c_regs *regs, uint8_t *data, int len)
{
        ASSERT(len);
 
        i2c_ack_enable(regs);
 
        int i;
        for (i = 0; i < len; i++) {
                if (i == len - 1)
                        i2c_ack_disable(regs);
 
                i2c_clear_int(regs);
                if (i2c_wait_for_int(regs, CONFIG_I2C_TRANSFER_TIMEOUT_US))
                        return 1;
 
                data[i] = read8(&regs->ds);
        }
 
        return 0;
}
 
int platform_i2c_transfer(unsigned int bus, struct i2c_msg *segments,
                          int seg_count)
{
        struct s3c24x0_i2c_bus *i2c = &i2c_busses[bus];
        struct i2c_regs *regs = i2c->regs;
        int res = 0;
 
        if (!regs || i2c_wait_for_idle(regs, I2C_TIMEOUT_US))
                return 1;
 
        write8(&regs->stat, I2cStatMasterXmit | I2cStatEnable);
 
        int i;
        for (i = 0; i < seg_count; i++) {
                struct i2c_msg *seg = &segments[i];
 
                res = i2c_send_start(regs, seg->flags & I2C_M_RD, seg->slave);
                if (res)
                        break;
                if (seg->flags & I2C_M_RD)
                        res = i2c_recv_buf(regs, seg->buf, seg->len);
                else
                        res = i2c_xmit_buf(regs, seg->buf, seg->len);
                if (res)
                        break;
        }
 
        return i2c_send_stop(regs) || res;
}
 
void i2c_init(unsigned int bus, int speed, int slaveadd)
{
        struct s3c24x0_i2c_bus *i2c = &i2c_busses[bus];
 
        unsigned long freq, pres = 16, div;
        unsigned long val;
 
        freq = clock_get_periph_rate(i2c->periph_id);
        // Calculate prescaler and divisor values.
        if ((freq / pres / (16 + 1)) > speed)
                /* set prescaler to 512 */
                pres = 512;
 
        div = 0;
 
        while ((freq / pres / (div + 1)) > speed)
                div++;
 
        // Set prescaler, divisor according to freq, also set ACKGEN, IRQ.
        val = (div & 0x0f) | 0xa0 | ((pres == 512) ? 0x40 : 0);
        write32(&i2c->regs->con, val);
 
        // Init to SLAVE RECEIVE mode and clear I2CADDn.
        write32(&i2c->regs->stat, 0);
        write32(&i2c->regs->add, slaveadd);
        // program Master Transmit (and implicit STOP).
        write32(&i2c->regs->stat, I2cStatMasterXmit | I2cStatEnable);
}