xiic_l.c

Uboot源码,非常通用的bootloader.适用于各种平台的Linux系统引导.

		 * occurs when the no ack is done to tell the slave the last byte
		 */
		if (ByteCount == 1) {
			IntrStatusMask =
				XIIC_INTR_ARB_LOST_MASK | XIIC_INTR_BNB_MASK;
		} else {
			IntrStatusMask =
				XIIC_INTR_ARB_LOST_MASK |
				XIIC_INTR_TX_ERROR_MASK | XIIC_INTR_BNB_MASK;
		}

		/* Wait for the previous transmit and the 1st receive to complete
		 * by checking the interrupt status register of the IPIF
		 */
		while (1) {
			IntrStatus = XIIF_V123B_READ_IISR (BaseAddress);
			if (IntrStatus & XIIC_INTR_RX_FULL_MASK) {
				break;
			}
			/* Check the transmit error after the receive full because when
			 * sending only one byte transmit error will occur because of the
			 * no ack to indicate the end of the data
			 */
			if (IntrStatus & IntrStatusMask) {
				return ByteCount;
			}
		}

		CntlReg = XIo_In8 (BaseAddress + XIIC_CR_REG_OFFSET);

		/* Special conditions exist for the last two bytes so check for them
		 * Note that the control register must be setup for these conditions
		 * before the data byte which was already received is read from the
		 * receive FIFO (while the bus is throttled
		 */
		if (ByteCount == 1) {
			/* For the last data byte, it has already been read and no ack
			 * has been done, so clear MSMS while leaving the device enabled
			 * so it can get off the IIC bus appropriately with a stop.
			 */
			XIo_Out8 (BaseAddress + XIIC_CR_REG_OFFSET,
				  XIIC_CR_ENABLE_DEVICE_MASK);
		}

		/* Before the last byte is received, set NOACK to tell the slave IIC
		 * device that it is the end, this must be done before reading the byte
		 * from the FIFO
		 */
		if (ByteCount == 2) {
			/* Write control reg with NO ACK allowing last byte to
			 * have the No ack set to indicate to slave last byte read.
			 */
			XIo_Out8 (BaseAddress + XIIC_CR_REG_OFFSET,
				  CntlReg | XIIC_CR_NO_ACK_MASK);
		}

		/* Read in data from the FIFO and unthrottle the bus such that the
		 * next byte is read from the IIC bus
		 */
		*BufferPtr++ = XIo_In8 (BaseAddress + XIIC_DRR_REG_OFFSET);

		/* Clear the latched interrupt status so that it will be updated with
		 * the new state when it changes, this must be done after the receive
		 * register is read
		 */
		XIic_mClearIisr (BaseAddress, XIIC_INTR_RX_FULL_MASK |
				 XIIC_INTR_TX_ERROR_MASK |
				 XIIC_INTR_ARB_LOST_MASK);
		ByteCount--;
	}

	/* Wait for the bus to transition to not busy before returning, the IIC
	 * device cannot be disabled until this occurs.	 It should transition as
	 * the MSMS bit of the control register was cleared before the last byte
	 * was read from the FIFO.
	 */
	while (1) {
		if (XIIF_V123B_READ_IISR (BaseAddress) & XIIC_INTR_BNB_MASK) {
			break;
		}
	}

	return ByteCount;
}

/****************************************************************************/
/**
* Send data as a master on the IIC bus.	 This function sends the data
* using polled I/O and blocks until the data has been sent.  It only supports
* 7 bit addressing and non-repeated start modes of operation.  The user is
* responsible for ensuring the bus is not busy if multiple masters are present
* on the bus.
*
* @param    BaseAddress contains the base address of the IIC device.
* @param    Address contains the 7 bit IIC address of the device to send the
*	    specified data to.
* @param    BufferPtr points to the data to be sent.
* @param    ByteCount is the number of bytes to be sent.
*
* @return
*
* The number of bytes sent.
*
* @note
*
* None
*
******************************************************************************/
unsigned XIic_Send (u32 BaseAddress, u8 Address,
		    u8 * BufferPtr, unsigned ByteCount)
{
	unsigned RemainingByteCount;

	/* Put the address into the FIFO to be sent and indicate that the operation
	 * to be performed on the bus is a write operation
	 */
	XIic_mSend7BitAddress (BaseAddress, Address, XIIC_WRITE_OPERATION);

	/* Clear the latched interrupt status so that it will be updated with the
	 * new state when it changes, this must be done after the address is put
	 * in the FIFO
	 */
	XIic_mClearIisr (BaseAddress, XIIC_INTR_TX_EMPTY_MASK |
			 XIIC_INTR_TX_ERROR_MASK | XIIC_INTR_ARB_LOST_MASK);

	/* MSMS must be set after putting data into transmit FIFO, indicate the
	 * direction is transmit, this device is master and enable the IIC device
	 */
	XIo_Out8 (BaseAddress + XIIC_CR_REG_OFFSET,
		  XIIC_CR_MSMS_MASK | XIIC_CR_DIR_IS_TX_MASK |
		  XIIC_CR_ENABLE_DEVICE_MASK);

	/* Clear the latched interrupt
	 * status for the bus not busy bit which must be done while the bus is busy
	 */
	XIic_mClearIisr (BaseAddress, XIIC_INTR_BNB_MASK);

	/* Send the specified data to the device on the IIC bus specified by the
	 * the address
	 */
	RemainingByteCount = SendData (BaseAddress, BufferPtr, ByteCount);

	/*
	 * The send is complete, disable the IIC device and return the number of
	 * bytes that was sent
	 */
	XIo_Out8 (BaseAddress + XIIC_CR_REG_OFFSET, 0);

	return ByteCount - RemainingByteCount;
}

/******************************************************************************
*
* Send the specified buffer to the device that has been previously addressed
* on the IIC bus.  This function assumes that the 7 bit address has been sent
* and it should wait for the transmit of the address to complete.
*
* @param    BaseAddress contains the base address of the IIC device.
* @param    BufferPtr points to the data to be sent.
* @param    ByteCount is the number of bytes to be sent.
*
* @return
*
* The number of bytes remaining to be sent.
*
* @note
*
* This function does not take advantage of the transmit FIFO because it is
* designed for minimal code space and complexity.  It contains loops that
* that could cause the function not to return if the hardware is not working.
*
******************************************************************************/
static unsigned SendData (u32 BaseAddress, u8 * BufferPtr, unsigned ByteCount)
{
	u32 IntrStatus;

	/* Send the specified number of bytes in the specified buffer by polling
	 * the device registers and blocking until complete
	 */
	while (ByteCount > 0) {
		/* Wait for the transmit to be empty before sending any more data
		 * by polling the interrupt status register
		 */
		while (1) {
			IntrStatus = XIIF_V123B_READ_IISR (BaseAddress);

			if (IntrStatus & (XIIC_INTR_TX_ERROR_MASK |
					  XIIC_INTR_ARB_LOST_MASK |
					  XIIC_INTR_BNB_MASK)) {
				return ByteCount;
			}

			if (IntrStatus & XIIC_INTR_TX_EMPTY_MASK) {
				break;
			}
		}
		/* If there is more than one byte to send then put the next byte to send
		 * into the transmit FIFO
		 */
		if (ByteCount > 1) {
			XIo_Out8 (BaseAddress + XIIC_DTR_REG_OFFSET,
				  *BufferPtr++);
		} else {
			/* Set the stop condition before sending the last byte of data so that
			 * the stop condition will be generated immediately following the data
			 * This is done by clearing the MSMS bit in the control register.
			 */
			XIo_Out8 (BaseAddress + XIIC_CR_REG_OFFSET,
				  XIIC_CR_ENABLE_DEVICE_MASK |
				  XIIC_CR_DIR_IS_TX_MASK);

			/* Put the last byte to send in the transmit FIFO */

			XIo_Out8 (BaseAddress + XIIC_DTR_REG_OFFSET,
				  *BufferPtr++);
		}

		/* Clear the latched interrupt status register and this must be done after
		 * the transmit FIFO has been written to or it won't clear
		 */
		XIic_mClearIisr (BaseAddress, XIIC_INTR_TX_EMPTY_MASK);

		/* Update the byte count to reflect the byte sent and clear the latched
		 * interrupt status so it will be updated for the new state
		 */
		ByteCount--;
	}

	/* Wait for the bus to transition to not busy before returning, the IIC
	 * device cannot be disabled until this occurs.
	 * Note that this is different from a receive operation because the stop
	 * condition causes the bus to go not busy.
	 */
	while (1) {
		if (XIIF_V123B_READ_IISR (BaseAddress) & XIIC_INTR_BNB_MASK) {
			break;
		}
	}

	return ByteCount;
}