xdma_channel_sg.c

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

	/* if a scatter gather list has not been created yet, return a status */

	if (InstancePtr->TotalDescriptorCount == 0) {
		return XST_DMA_SG_NO_LIST;
	}

	/* if the buffer descriptor list is empty, then indicate an error */

	if (XDmaChannel_IsSgListEmpty(InstancePtr)) {
		return XST_DMA_SG_LIST_EMPTY;
	}

	/* retrieve the next buffer descriptor which is ready to be processed from
	 * the buffer descriptor list for the DMA channel, set the control word
	 * such that hardware will stop after the descriptor has been processed
	 */
	Control = XBufDescriptor_GetControl(InstancePtr->GetPtr);
	XBufDescriptor_SetControl(InstancePtr->GetPtr,
				  Control | XDC_DMACR_SG_DISABLE_MASK);

	/* set the input argument, which is also an output, to point to the
	 * buffer descriptor which is to be retrieved from the list
	 */
	*BufDescriptorPtr = InstancePtr->GetPtr;

	/* update the pointer of the DMA channel to reflect the buffer descriptor
	 * was retrieved from the list by setting it to the next buffer descriptor
	 * in the list and indicate one less descriptor in the list now
	 */
	InstancePtr->GetPtr = XBufDescriptor_GetNextPtr(InstancePtr->GetPtr);
	InstancePtr->ActiveDescriptorCount--;

	return XST_SUCCESS;
}

/*********************** Interrupt Collescing Functions **********************/

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_GetPktCount
*
* DESCRIPTION:
*
* This function returns the value of the unserviced packet count register of
* the DMA channel.  This count represents the number of packets that have been
* sent or received by the hardware, but not processed by software.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* RETURN VALUE:
*
* The unserviced packet counter register contents for the DMA channel.
*
* NOTES:
*
* None.
*
******************************************************************************/
u32
XDmaChannel_GetPktCount(XDmaChannel * InstancePtr)
{
	/* assert to verify input arguments */

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

	/* get the unserviced packet count from the register and return it */

	return XIo_In32(InstancePtr->RegBaseAddress + XDC_UPC_REG_OFFSET);
}

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_DecrementPktCount
*
* DESCRIPTION:
*
* This function decrements the value of the unserviced packet count register.
* This informs the hardware that the software has processed a packet.  The
* unserviced packet count register may only be decremented by one in the
* hardware.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* RETURN VALUE:
*
* None.
*
* NOTES:
*
* None.
*
******************************************************************************/
void
XDmaChannel_DecrementPktCount(XDmaChannel * InstancePtr)
{
	u32 Register;

	/* assert to verify input arguments */

	XASSERT_VOID(InstancePtr != NULL);
	XASSERT_VOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);

	/* if the unserviced packet count register can be decremented (rather
	 * than rolling over) decrement it by writing a 1 to the register,
	 * this is the only valid write to the register as it serves as an
	 * acknowledge that a packet was handled by the software
	 */
	Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_UPC_REG_OFFSET);
	if (Register > 0) {
		XIo_Out32(InstancePtr->RegBaseAddress + XDC_UPC_REG_OFFSET,
			  1UL);
	}
}

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_SetPktThreshold
*
* DESCRIPTION:
*
* This function sets the value of the packet count threshold register of the
* DMA channel.	It reflects the number of packets that must be sent or
* received before generating an interrupt.  This value helps implement
* a concept called "interrupt coalescing", which is used to reduce the number
* of interrupts from devices with high data rates.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* Threshold is the value that is written to the threshold register of the
* DMA channel.
*
* RETURN VALUE:
*
* A status containing XST_SUCCESS if the packet count threshold was
* successfully set.
*
* NOTES:
*
* The packet threshold could be set to larger than the number of descriptors
* allocated to the DMA channel. In this case, the wait bound will take over
* and always indicate data arrival. There was a check in this function that
* returned an error if the treshold was larger than the number of descriptors,
* but that was removed because users would then have to set the threshold
* only after they set descriptor space, which is an order dependency that
* caused confustion.
*
******************************************************************************/
XStatus
XDmaChannel_SetPktThreshold(XDmaChannel * InstancePtr, u8 Threshold)
{
	/* assert to verify input arguments, don't assert the threshold since
	 * it's range is unknown
	 */
	XASSERT_NONVOID(InstancePtr != NULL);
	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);

	/* set the packet count threshold in the register such that an interrupt
	 * may be generated, if enabled, when the packet count threshold is
	 * reached or exceeded
	 */
	XIo_Out32(InstancePtr->RegBaseAddress + XDC_PCT_REG_OFFSET,
		  (u32) Threshold);

	/* indicate the packet count threshold was successfully set */

	return XST_SUCCESS;
}

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_GetPktThreshold
*
* DESCRIPTION:
*
* This function gets the value of the packet count threshold register of the
* DMA channel.	This value reflects the number of packets that must be sent or
* received before generating an interrupt.  This value helps implement a concept
* called "interrupt coalescing", which is used to reduce the number of
* interrupts from devices with high data rates.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* RETURN VALUE:
*
* The packet threshold register contents for the DMA channel and is a value in
* the range 0 - 1023.  A value of 0 indicates the packet wait bound timer is
* disabled.
*
* NOTES:
*
* None.
*
******************************************************************************/
u8
XDmaChannel_GetPktThreshold(XDmaChannel * InstancePtr)
{
	/* assert to verify input arguments */

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

	/* get the packet count threshold from the register and return it,
	 * since only 8 bits are used, cast it to return only those bits */

	return (u8) XIo_In32(InstancePtr->RegBaseAddress + XDC_PCT_REG_OFFSET);
}

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_SetPktWaitBound
*
* DESCRIPTION:
*
* This function sets the value of the packet wait bound register of the
* DMA channel.	This value reflects the timer value used to trigger an
* interrupt when not enough packets have been received to reach the packet
* count threshold.
*
* The timer is in millisecond units with +/- 33% accuracy.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* WaitBound is the value, in milliseconds, to be stored in the wait bound
* register of the DMA channel and is a value in the range 0  - 1023.  A value
* of 0 disables the packet wait bound timer.
*
* RETURN VALUE:
*
* None.
*
* NOTES:
*
* None.
*
******************************************************************************/
void
XDmaChannel_SetPktWaitBound(XDmaChannel * InstancePtr, u32 WaitBound)
{
	/* assert to verify input arguments */

	XASSERT_VOID(InstancePtr != NULL);
	XASSERT_VOID(WaitBound < 1024);
	XASSERT_VOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);

	/* set the packet wait bound in the register such that interrupt may be
	 * generated, if enabled, when packets have not been handled for a specific
	 * amount of time
	 */
	XIo_Out32(InstancePtr->RegBaseAddress + XDC_PWB_REG_OFFSET, WaitBound);
}

/******************************************************************************
*
* FUNCTION:
*
* XDmaChannel_GetPktWaitBound
*
* DESCRIPTION:
*
* This function gets the value of the packet wait bound register of the
* DMA channel.	This value contains the timer value used to trigger an
* interrupt when not enough packets have been received to reach the packet
* count threshold.
*
* The timer is in millisecond units with +/- 33% accuracy.
*
* ARGUMENTS:
*
* InstancePtr contains a pointer to the DMA channel to operate on.  The DMA
* channel should be configured to use scatter gather in order for this function
* to be called.
*
* RETURN VALUE:
*
* The packet wait bound register contents for the DMA channel.
*
* NOTES:
*
* None.
*
******************************************************************************/
u32
XDmaChannel_GetPktWaitBound(XDmaChannel * InstancePtr)
{
	/* assert to verify input arguments */

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

	/* get the packet wait bound from the register and return it */

	return XIo_In32(InstancePtr->RegBaseAddress + XDC_PWB_REG_OFFSET);
}