xemac_polled.c

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	 * Overrun errors
	 */
	if (IntrStatus & (XEM_EIR_XMIT_SFIFO_OVER_MASK |
			  XEM_EIR_XMIT_LFIFO_OVER_MASK)) {
		InstancePtr->Stats.XmitOverrunErrors++;
		InstancePtr->Stats.FifoErrors++;
		return XST_FIFO_ERROR;
	}

	/*
	 * Underrun errors
	 */
	if (IntrStatus & (XEM_EIR_XMIT_SFIFO_UNDER_MASK |
			  XEM_EIR_XMIT_LFIFO_UNDER_MASK)) {
		InstancePtr->Stats.XmitUnderrunErrors++;
		InstancePtr->Stats.FifoErrors++;
		return XST_FIFO_ERROR;
	}

	/*
	 * Clear the interrupt status register of transmit statuses
	 */
	XIIF_V123B_WRITE_IISR(InstancePtr->BaseAddress,
			      IntrStatus & XEM_EIR_XMIT_ALL_MASK);

	/*
	 * Collision errors are stored in the transmit status register
	 * instead of the interrupt status register
	 */
	if (XmitStatus & XEM_TSR_EXCESS_DEFERRAL_MASK) {
		InstancePtr->Stats.XmitExcessDeferral++;
		return XST_EMAC_COLLISION_ERROR;
	}

	if (XmitStatus & XEM_TSR_LATE_COLLISION_MASK) {
		InstancePtr->Stats.XmitLateCollisionErrors++;
		return XST_EMAC_COLLISION_ERROR;
	}

	return XST_SUCCESS;
}

/*****************************************************************************/
/**
*
* Receive an Ethernet frame in polled mode. The device/driver must be in polled
* mode before calling this function. The driver receives the frame directly
* from the MAC's packet FIFO. This is a non-blocking receive, in that if there
* is no frame ready to be received at the device, the function returns with an
* error. The MAC's error status is not checked, so statistics are not updated
* for polled receive. The buffer into which the frame will be received must be
* word-aligned.
*
* @param InstancePtr is a pointer to the XEmac instance to be worked on.
* @param BufPtr is a pointer to a word-aligned buffer into which the received
*        Ethernet frame will be copied.
* @param ByteCountPtr is both an input and an output parameter. It is a pointer
*        to a 32-bit word that contains the size of the buffer on entry into the
*        function and the size the received frame on return from the function.
*
* @return
*
* - XST_SUCCESS if the frame was sent successfully
* - XST_DEVICE_IS_STOPPED if the device has not yet been started
* - XST_NOT_POLLED if the device is not in polled mode
* - XST_NO_DATA if there is no frame to be received from the FIFO
* - XST_BUFFER_TOO_SMALL if the buffer to receive the frame is too small for
*   the frame waiting in the FIFO.
*
* @note
*
* Input buffer must be big enough to hold the largest Ethernet frame. Buffer
* must also be 32-bit aligned.
*
* @internal
*
* The EMAC uses FIFOs behind its length and status registers. For this reason,
* it is important to keep the length, status, and data FIFOs in sync when
* reading or writing to them.
*
******************************************************************************/
XStatus
XEmac_PollRecv(XEmac * InstancePtr, u8 * BufPtr, u32 * ByteCountPtr)
{
	XStatus Result;
	u32 PktLength;
	u32 IntrStatus;

	XASSERT_NONVOID(InstancePtr != NULL);
	XASSERT_NONVOID(BufPtr != NULL);
	XASSERT_NONVOID(ByteCountPtr != NULL);
	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);

	/*
	 * Be sure the device is configured for polled mode and it is started
	 */
	if (!InstancePtr->IsPolled) {
		return XST_NOT_POLLED;
	}

	if (InstancePtr->IsStarted != XCOMPONENT_IS_STARTED) {
		return XST_DEVICE_IS_STOPPED;
	}

	/*
	 * Make sure the buffer is big enough to hold the maximum frame size.
	 * We need to do this because as soon as we read the MAC's packet length
	 * register, which is actually a FIFO, we remove that length from the
	 * FIFO.  We do not want to read the length FIFO without also reading the
	 * data FIFO since this would get the FIFOs out of sync.  So we have to
	 * make this restriction.
	 */
	if (*ByteCountPtr < XEM_MAX_FRAME_SIZE) {
		return XST_BUFFER_TOO_SMALL;
	}

	/*
	 * First check for packet FIFO deadlock and return an error if it has
	 * occurred. A reset by the caller is necessary to correct this problem.
	 */
	if (XPF_V100B_IS_DEADLOCKED(&InstancePtr->RecvFifo)) {
		InstancePtr->Stats.FifoErrors++;
		return XST_FIFO_ERROR;
	}

	/*
	 * Get the interrupt status to know what happened (whether an error occurred
	 * and/or whether frames have been received successfully). When clearing the
	 * intr status register, clear only statuses that pertain to receive.
	 */
	IntrStatus = XIIF_V123B_READ_IISR(InstancePtr->BaseAddress);
	XIIF_V123B_WRITE_IISR(InstancePtr->BaseAddress,
			      IntrStatus & XEM_EIR_RECV_ALL_MASK);

	/*
	 * Check receive errors and bump statistics so the caller will have a clue
	 * as to why data may not have been received. We continue on if an error
	 * occurred since there still may be frames that were received successfully.
	 */
	if (IntrStatus & (XEM_EIR_RECV_LFIFO_OVER_MASK |
			  XEM_EIR_RECV_DFIFO_OVER_MASK)) {
		InstancePtr->Stats.RecvOverrunErrors++;
		InstancePtr->Stats.FifoErrors++;
	}

	if (IntrStatus & XEM_EIR_RECV_LFIFO_UNDER_MASK) {
		InstancePtr->Stats.RecvUnderrunErrors++;
		InstancePtr->Stats.FifoErrors++;
	}

	/*
	 * General receive errors
	 */
	if (IntrStatus & XEM_EIR_RECV_ERROR_MASK) {
		if (IntrStatus & XEM_EIR_RECV_MISSED_FRAME_MASK) {
			InstancePtr->Stats.RecvMissedFrameErrors =
			    XIo_In32(InstancePtr->BaseAddress +
				     XEM_RMFC_OFFSET);
		}

		if (IntrStatus & XEM_EIR_RECV_COLLISION_MASK) {
			InstancePtr->Stats.RecvCollisionErrors =
			    XIo_In32(InstancePtr->BaseAddress + XEM_RCC_OFFSET);
		}

		if (IntrStatus & XEM_EIR_RECV_FCS_ERROR_MASK) {
			InstancePtr->Stats.RecvFcsErrors =
			    XIo_In32(InstancePtr->BaseAddress +
				     XEM_RFCSEC_OFFSET);
		}

		if (IntrStatus & XEM_EIR_RECV_LEN_ERROR_MASK) {
			InstancePtr->Stats.RecvLengthFieldErrors++;
		}

		if (IntrStatus & XEM_EIR_RECV_SHORT_ERROR_MASK) {
			InstancePtr->Stats.RecvShortErrors++;
		}

		if (IntrStatus & XEM_EIR_RECV_LONG_ERROR_MASK) {
			InstancePtr->Stats.RecvLongErrors++;
		}

		if (IntrStatus & XEM_EIR_RECV_ALIGN_ERROR_MASK) {
			InstancePtr->Stats.RecvAlignmentErrors =
			    XIo_In32(InstancePtr->BaseAddress +
				     XEM_RAEC_OFFSET);
		}
	}

	/*
	 * Before reading from the length FIFO, make sure the length FIFO is not
	 * empty. We could cause an underrun error if we try to read from an
	 * empty FIFO.
	 */
	if ((IntrStatus & XEM_EIR_RECV_DONE_MASK) == 0) {
		return XST_NO_DATA;
	}

	/*
	 * Determine, from the MAC, the length of the next packet available
	 * in the data FIFO (there should be a non-zero length here)
	 */
	PktLength = XIo_In32(InstancePtr->BaseAddress + XEM_RPLR_OFFSET);
	if (PktLength == 0) {
		return XST_NO_DATA;
	}

	/*
	 * Write the RECV_DONE bit in the status register to clear it. This bit
	 * indicates the RPLR is non-empty, and we know it's set at this point.
	 * We clear it so that subsequent entry into this routine will reflect the
	 * current status. This is done because the non-empty bit is latched in the
	 * IPIF, which means it may indicate a non-empty condition even though
	 * there is something in the FIFO.
	 */
	XIIF_V123B_WRITE_IISR(InstancePtr->BaseAddress, XEM_EIR_RECV_DONE_MASK);

	/*
	 * We assume that the MAC never has a length bigger than the largest
	 * Ethernet frame, so no need to make another check here.
	 */

	/*
	 * This is a non-blocking read. The FIFO returns an error if there is
	 * not at least the requested amount of data in the FIFO.
	 */
	Result =
	    XPacketFifoV100b_Read(&InstancePtr->RecvFifo, BufPtr, PktLength);
	if (Result != XST_SUCCESS) {
		return Result;
	}

	InstancePtr->Stats.RecvFrames++;
	InstancePtr->Stats.RecvBytes += PktLength;

	*ByteCountPtr = PktLength;

	return XST_SUCCESS;
}