static int i2c_s3c_irq_nextbyte()

in busses/i2c-s3c2410.c [384:552]

• 94 lines of code
• 24 McCabe index (conditional complexity)

static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
{
	unsigned long tmp;
	unsigned char byte;
	int ret = 0;

	switch (i2c->state) {

	case STATE_IDLE:
		dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __func__);
		goto out;

	case STATE_STOP:
		dev_err(i2c->dev, "%s: called in STATE_STOP\n", __func__);
		s3c24xx_i2c_disable_irq(i2c);
		goto out_ack;

	case STATE_START:
		/*
		 * last thing we did was send a start condition on the
		 * bus, or started a new i2c message
		 */
		if (iicstat & S3C2410_IICSTAT_LASTBIT &&
		    !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
			/* ack was not received... */
			dev_dbg(i2c->dev, "ack was not received\n");
			s3c24xx_i2c_stop(i2c, -ENXIO);
			goto out_ack;
		}

		if (i2c->msg->flags & I2C_M_RD)
			i2c->state = STATE_READ;
		else
			i2c->state = STATE_WRITE;

		/*
		 * Terminate the transfer if there is nothing to do
		 * as this is used by the i2c probe to find devices.
		 */
		if (is_lastmsg(i2c) && i2c->msg->len == 0) {
			s3c24xx_i2c_stop(i2c, 0);
			goto out_ack;
		}

		if (i2c->state == STATE_READ)
			goto prepare_read;

		/*
		 * fall through to the write state, as we will need to
		 * send a byte as well
		 */
		fallthrough;
	case STATE_WRITE:
		/*
		 * we are writing data to the device... check for the
		 * end of the message, and if so, work out what to do
		 */
		if (!(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
			if (iicstat & S3C2410_IICSTAT_LASTBIT) {
				dev_dbg(i2c->dev, "WRITE: No Ack\n");

				s3c24xx_i2c_stop(i2c, -ECONNREFUSED);
				goto out_ack;
			}
		}

 retry_write:

		if (!is_msgend(i2c)) {
			byte = i2c->msg->buf[i2c->msg_ptr++];
			writeb(byte, i2c->regs + S3C2410_IICDS);

			/*
			 * delay after writing the byte to allow the
			 * data setup time on the bus, as writing the
			 * data to the register causes the first bit
			 * to appear on SDA, and SCL will change as
			 * soon as the interrupt is acknowledged
			 */
			ndelay(i2c->tx_setup);

		} else if (!is_lastmsg(i2c)) {
			/* we need to go to the next i2c message */

			dev_dbg(i2c->dev, "WRITE: Next Message\n");

			i2c->msg_ptr = 0;
			i2c->msg_idx++;
			i2c->msg++;

			/* check to see if we need to do another message */
			if (i2c->msg->flags & I2C_M_NOSTART) {

				if (i2c->msg->flags & I2C_M_RD) {
					/*
					 * cannot do this, the controller
					 * forces us to send a new START
					 * when we change direction
					 */
					dev_dbg(i2c->dev,
						"missing START before write->read\n");
					s3c24xx_i2c_stop(i2c, -EINVAL);
					break;
				}

				goto retry_write;
			} else {
				/* send the new start */
				s3c24xx_i2c_message_start(i2c, i2c->msg);
				i2c->state = STATE_START;
			}

		} else {
			/* send stop */
			s3c24xx_i2c_stop(i2c, 0);
		}
		break;

	case STATE_READ:
		/*
		 * we have a byte of data in the data register, do
		 * something with it, and then work out whether we are
		 * going to do any more read/write
		 */
		byte = readb(i2c->regs + S3C2410_IICDS);
		i2c->msg->buf[i2c->msg_ptr++] = byte;

		/* Add actual length to read for smbus block read */
		if (i2c->msg->flags & I2C_M_RECV_LEN && i2c->msg->len == 1)
			i2c->msg->len += byte;
 prepare_read:
		if (is_msglast(i2c)) {
			/* last byte of buffer */

			if (is_lastmsg(i2c))
				s3c24xx_i2c_disable_ack(i2c);

		} else if (is_msgend(i2c)) {
			/*
			 * ok, we've read the entire buffer, see if there
			 * is anything else we need to do
			 */
			if (is_lastmsg(i2c)) {
				/* last message, send stop and complete */
				dev_dbg(i2c->dev, "READ: Send Stop\n");

				s3c24xx_i2c_stop(i2c, 0);
			} else {
				/* go to the next transfer */
				dev_dbg(i2c->dev, "READ: Next Transfer\n");

				i2c->msg_ptr = 0;
				i2c->msg_idx++;
				i2c->msg++;
			}
		}

		break;
	}

	/* acknowlegde the IRQ and get back on with the work */

 out_ack:
	tmp = readl(i2c->regs + S3C2410_IICCON);
	tmp &= ~S3C2410_IICCON_IRQPEND;
	writel(tmp, i2c->regs + S3C2410_IICCON);
 out:
	return ret;
}