diff options
| -rw-r--r-- | drivers/i2c/mxc_i2c.c | 95 |
1 files changed, 64 insertions, 31 deletions
diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c index f17a47f..23119cc 100644 --- a/drivers/i2c/mxc_i2c.c +++ b/drivers/i2c/mxc_i2c.c @@ -482,8 +482,13 @@ static int i2c_write_data(struct mxc_i2c_bus *i2c_bus, u8 chip, const u8 *buf, return ret; } +/* Will generate a STOP after the last byte if "last" is true, i.e. this is the + * final message of a transaction. If not, it switches the bus back to TX mode + * and does not send a STOP, leaving the bus in a state where a repeated start + * and address can be sent for another message. + */ static int i2c_read_data(struct mxc_i2c_bus *i2c_bus, uchar chip, uchar *buf, - int len) + int len, bool last) { int ret; unsigned int temp; @@ -513,17 +518,31 @@ static int i2c_read_data(struct mxc_i2c_bus *i2c_bus, uchar chip, uchar *buf, return ret; } - /* - * It must generate STOP before read I2DR to prevent - * controller from generating another clock cycle - */ if (i == (len - 1)) { - i2c_imx_stop(i2c_bus); + /* Final byte has already been received by master! When + * we read it from I2DR, the master will start another + * cycle. We must program it first to send a STOP or + * switch to TX to avoid this. + */ + if (last) { + i2c_imx_stop(i2c_bus); + } else { + /* Final read, no stop, switch back to tx */ + temp = readb(base + (I2CR << reg_shift)); + temp |= I2CR_MTX | I2CR_TX_NO_AK; + writeb(temp, base + (I2CR << reg_shift)); + } } else if (i == (len - 2)) { + /* Master has already recevied penultimate byte. When + * we read it from I2DR, master will start RX of final + * byte. We must set TX_NO_AK now so it does not ACK + * that final byte. + */ temp = readb(base + (I2CR << reg_shift)); temp |= I2CR_TX_NO_AK; writeb(temp, base + (I2CR << reg_shift)); } + writeb(I2SR_IIF_CLEAR, base + (I2SR << reg_shift)); buf[i] = readb(base + (I2DR << reg_shift)); } @@ -533,7 +552,9 @@ static int i2c_read_data(struct mxc_i2c_bus *i2c_bus, uchar chip, uchar *buf, debug(" 0x%02x", buf[ret]); debug("\n"); - i2c_imx_stop(i2c_bus); + /* It is not clear to me that this is necessary */ + if (last) + i2c_imx_stop(i2c_bus); return 0; } @@ -585,7 +606,7 @@ static int bus_i2c_read(struct mxc_i2c_bus *i2c_bus, u8 chip, u32 addr, return ret; } - ret = i2c_read_data(i2c_bus, chip, buf, len); + ret = i2c_read_data(i2c_bus, chip, buf, len, true); i2c_imx_stop(i2c_bus); return ret; @@ -939,42 +960,54 @@ static int mxc_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs) ulong base = i2c_bus->base; int reg_shift = i2c_bus->driver_data & I2C_QUIRK_FLAG ? VF610_I2C_REGSHIFT : IMX_I2C_REGSHIFT; + int read_mode; - /* - * Here the 3rd parameter addr and the 4th one alen are set to 0, - * because here we only want to send out chip address. The register - * address is wrapped in msg. + /* Here address len is set to -1 to not send any address at first. + * Otherwise i2c_init_transfer will send the chip address with write + * mode set. This is wrong if the 1st message is read. */ - ret = i2c_init_transfer(i2c_bus, msg->addr, 0, 0); + ret = i2c_init_transfer(i2c_bus, msg->addr, 0, -1); if (ret < 0) { debug("i2c_init_transfer error: %d\n", ret); return ret; } + read_mode = -1; /* So it's always different on the first message */ for (; nmsgs > 0; nmsgs--, msg++) { - bool next_is_read = nmsgs > 1 && (msg[1].flags & I2C_M_RD); - debug("i2c_xfer: chip=0x%x, len=0x%x\n", msg->addr, msg->len); - if (msg->flags & I2C_M_RD) - ret = i2c_read_data(i2c_bus, msg->addr, msg->buf, - msg->len); - else { - ret = i2c_write_data(i2c_bus, msg->addr, msg->buf, - msg->len); - if (ret) - break; - if (next_is_read) { - /* Reuse ret */ + const int msg_is_read = !!(msg->flags & I2C_M_RD); + + debug("i2c_xfer: chip=0x%x, len=0x%x, dir=%c\n", msg->addr, + msg->len, msg_is_read ? 'R' : 'W'); + + if (msg_is_read != read_mode) { + /* Send repeated start if not 1st message */ + if (read_mode != -1) { + debug("i2c_xfer: [RSTART]\n"); ret = readb(base + (I2CR << reg_shift)); ret |= I2CR_RSTA; writeb(ret, base + (I2CR << reg_shift)); - - ret = tx_byte(i2c_bus, (msg->addr << 1) | 1); - if (ret < 0) { - i2c_imx_stop(i2c_bus); - break; - } } + debug("i2c_xfer: [ADDR %02x | %c]\n", msg->addr, + msg_is_read ? 'R' : 'W'); + ret = tx_byte(i2c_bus, (msg->addr << 1) | msg_is_read); + if (ret < 0) { + debug("i2c_xfer: [STOP]\n"); + i2c_imx_stop(i2c_bus); + break; + } + read_mode = msg_is_read; } + + if (msg->flags & I2C_M_RD) + ret = i2c_read_data(i2c_bus, msg->addr, msg->buf, + msg->len, nmsgs == 1 || + (msg->flags & I2C_M_STOP)); + else + ret = i2c_write_data(i2c_bus, msg->addr, msg->buf, + msg->len); + + if (ret < 0) + break; } if (ret) |