/* $Id: xdma_channel_sg.c,v 1.6 2003/02/03 19:50:33 moleres Exp $ */ /****************************************************************************** * * Author: Xilinx, Inc. * * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2 of the License, or (at your * option) any later version. * * * XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A * COURTESY TO YOU. BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS * ONE POSSIBLE IMPLEMENTATION OF THIS FEATURE, APPLICATION OR STANDARD, * XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION IS FREE * FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE FOR OBTAINING * ANY THIRD PARTY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION. * XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO * THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO ANY * WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE FROM * CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY AND * FITNESS FOR A PARTICULAR PURPOSE. * * * Xilinx hardware products are not intended for use in life support * appliances, devices, or systems. Use in such applications is * expressly prohibited. * * * (c) Copyright 2002-2004 Xilinx Inc. * All rights reserved. * * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 675 Mass Ave, Cambridge, MA 02139, USA. * * FILENAME: * * xdma_channel_sg.c * * DESCRIPTION: * * This file contains the implementation of the XDmaChannel component which is * related to scatter gather operations. * * Scatter Gather Operations * * The DMA channel may support scatter gather operations. A scatter gather * operation automates the DMA channel such that multiple buffers can be * sent or received with minimal software interaction with the hardware. Buffer * descriptors, contained in the XBufDescriptor component, are used by the * scatter gather operations of the DMA channel to describe the buffers to be * processed. * * Scatter Gather List Operations * * A scatter gather list may be supported by each DMA channel. The scatter * gather list allows buffer descriptors to be put into the list by a device * driver which requires scatter gather. The hardware processes the buffer * descriptors which are contained in the list and modifies the buffer * descriptors to reflect the status of the DMA operations. The device driver * is notified by interrupt that specific DMA events occur including scatter * gather events. The device driver removes the completed buffer descriptors * from the scatter gather list to evaluate the status of each DMA operation. * * The scatter gather list is created and buffer descriptors are inserted into * the list. Buffer descriptors are never removed from the list after it's * creation such that a put operation copies from a temporary buffer descriptor * to a buffer descriptor in the list. Get operations don't copy from the list * to a temporary, but return a pointer to the buffer descriptor in the list. * A buffer descriptor in the list may be locked to prevent it from being * overwritten by a put operation. This allows the device driver to get a * descriptor from a scatter gather list and prevent it from being overwritten * until the buffer associated with the buffer descriptor has been processed. * * The get and put functions only operate on the list and are asynchronous from * the hardware which may be using the list of descriptors. This is important * because there are no checks in the get and put functions to ensure that the * hardware has processed the descriptors. This must be handled by the driver * using the DMA scatter gather channel through the use of the other functions. * When a scatter gather operation is started, the start function does ensure * that the descriptor to start has not already been processed by the hardware * and is not the first of a series of descriptors that have not been committed * yet. * * Descriptors are put into the list but not marked as ready to use by the * hardware until a commit operation is done. This allows multiple descriptors * which may contain a single packet of information for a protocol to be * guaranteed not to cause any underflow conditions during transmission. The * hardware design only allows descriptors to cause it to stop after a descriptor * has been processed rather than before it is processed. A series of * descriptors are put into the list followed by a commit operation, or each * descriptor may be commited. A commit operation is performed by changing a * single descriptor, the first of the series of puts, to indicate that the * hardware may now use all descriptors after it. The last descriptor in the * list is always set to cause the hardware to stop after it is processed. * * Typical Scatter Gather Processing * * The following steps illustrate the typical processing to use the * scatter gather features of a DMA channel. * * 1. Create a scatter gather list for the DMA channel which puts empty buffer * descriptors into the list. * 2. Create buffer descriptors which describe the buffers to be filled with * receive data or the buffers which contain data to be sent. * 3. Put buffer descriptors into the DMA channel scatter list such that scatter * gather operations are requested. * 4. Commit the buffer descriptors in the list such that they are ready to be * used by the DMA channel hardware. * 5. Start the scatter gather operations of the DMA channel. * 6. Process any interrupts which occur as a result of the scatter gather * operations or poll the DMA channel to determine the status. This may * be accomplished by getting the packet count for the channel and then * getting the appropriate number of descriptors from the list for that * number of packets. * * Minimizing Interrupts * * The Scatter Gather operating mode is designed to reduce the amount of CPU * throughput necessary to manage the hardware for devices. A key to the CPU * throughput is the number and rate of interrupts that the CPU must service. * Devices with higher data rates can cause larger numbers of interrupts and * higher frequency interrupts. Ideally the number of interrupts can be reduced * by only generating an interrupt when a specific amount of data has been * received from the interface. This design suffers from a lack of interrupts * when the amount of data received is less than the specified amount of data * to generate an interrupt. In order to help minimize the number of interrupts * which the CPU must service, an algorithm referred to as "interrupt coalescing" * is utilized. * * Interrupt Coalescing * * The principle of interrupt coalescing is to wait before generating an * interrupt until a certain number of packets have been received or sent. An * interrupt is also generated if a smaller number of packets have been received * followed by a certain period of time with no packet reception. This is a * trade-off of latency for bandwidth and is accomplished using several * mechanisms of the hardware including a counter for packets received or * transmitted and a packet timer. These two hardware mechanisms work in * combination to allow a reduction in the number of interrupts processed by the * CPU for packet reception. * * Unserviced Packet Count * * The purpose of the packet counter is to count the number of packets received * or transmitted and provide an interrupt when a specific number of packets * have been processed by the hardware. An interrupt is generated whenever the * counter is greater than or equal to the Packet Count Threshold. This counter * contains an accurate count of the number of packets that the hardware has * processed, either received or transmitted, and the software has not serviced. * * The packet counter allows the number of interrupts to be reduced by waiting * to generate an interrupt until enough packets are received. For packet * reception, packet counts of less than the number to generate an interrupt * would not be serviced without the addition of a packet timer. This counter is * continuously updated by the hardware, not latched to the value at the time * the interrupt occurred. * * The packet counter can be used within the interrupt service routine for the * device to reduce the number of interrupts. The interrupt service routine * loops while performing processing for each packet which has been received or * transmitted and decrements the counter by a specified value. At the same time, * the hardware is possibly continuing to receive or transmit more packets such * that the software may choose, based upon the value in the packet counter, to * remain in the interrupt service routine rather than exiting and immediately * returning. This feature should be used with caution as reducing the number of * interrupts is beneficial, but unbounded interrupt processing is not desirable. * * Since the hardware may be incrementing the packet counter simultaneously * with the software decrementing the counter, there is a need for atomic * operations. The hardware ensures that the operation is atomic such that * simultaneous accesses are properly handled. * * Packet Wait Bound * * The purpose of the packet wait bound is to augment the unserviced packet * count. Whenever there is no pending interrupt for the channel and the * unserviced packet count is non-zero, a timer starts counting timeout at the * value contained the the packet wait bound register. If the timeout is * reached, an interrupt is generated such that the software may service the * data which was buffered. * * NOTES: * * Special Test Conditions: * * The scatter gather list processing must be thoroughly tested if changes are * made. Testing should include putting and committing single descriptors and * putting multiple descriptors followed by a single commit. There are some * conditions in the code which handle the exception conditions. * * The Put Pointer points to the next location in the descriptor list to copy * in a new descriptor. The Get Pointer points to the next location in the * list to get a descriptor from. The Get Pointer only allows software to * have a traverse the list after the hardware has finished processing some * number of descriptors. The Commit Pointer points to the descriptor in the * list which is to be committed. It is also used to determine that no * descriptor is waiting to be commited (NULL). The Last Pointer points to * the last descriptor that was put into the list. It typically points * to the previous descriptor to the one pointed to by the Put Pointer. * Comparisons are done between these pointers to determine when the following * special conditions exist. * Single Put And Commit * * The buffer descriptor is ready to be used by the hardware so it is important * for the descriptor to not appear to be waiting to be committed. The commit * pointer is reset when a commit is done indicating there are no descriptors * waiting to be committed. In all cases but this one, the descriptor is * changed to cause the hardware to go to the next descriptor after processing * this one. But in this case, this is the last descriptor in the list such * that it must not be changed. * * 3 Or More Puts And Commit * * A series of 3 or more puts followed by a single commit is different in that * only the 1st descriptor put into the list is changed when the commit is done. * This requires each put starting on the 3rd to change the previous descriptor * so that it allows the hardware to continue to the next descriptor in the list. * * The 1st Put Following A Commit * * The commit caused the commit pointer to be NULL indicating that there are no * descriptors waiting to be committed. It is necessary for the next put to set * the commit pointer so that a commit must follow the put for the hardware to * use the descriptor. * * 
* MODIFICATION HISTORY:
*
* Ver	Who  Date     Changes
* ----- ---- -------- ------------------------------------------------------
* 1.00a rpm  02/03/03 Removed the XST_DMA_SG_COUNT_EXCEEDED return code
*		      from SetPktThreshold.
*
* ******************************************************************************/ /***************************** Include Files *********************************/ #include "xdma_channel.h" #include "xbasic_types.h" #include "xio.h" #include "xbuf_descriptor.h" #include "xstatus.h" /************************** Constant Definitions *****************************/ #define XDC_SWCR_SG_ENABLE_MASK 0x80000000UL /* scatter gather enable */ /**************************** Type Definitions *******************************/ /***************** Macros (Inline Functions) Definitions *********************/ /* the following macro copies selected fields of a buffer descriptor to another * buffer descriptor, this was provided by the buffer descriptor component but * was moved here since it is only used internally to this component and since * it does not copy all fields */ #define CopyBufferDescriptor(InstancePtr, DestinationPtr) \ { \ *((u32 *)DestinationPtr + XBD_CONTROL_OFFSET) = \ *((u32 *)InstancePtr + XBD_CONTROL_OFFSET); \ *((u32 *)DestinationPtr + XBD_SOURCE_OFFSET) = \ *((u32 *)InstancePtr + XBD_SOURCE_OFFSET); \ *((u32 *)DestinationPtr + XBD_DESTINATION_OFFSET) = \ *((u32 *)InstancePtr + XBD_DESTINATION_OFFSET); \ *((u32 *)DestinationPtr + XBD_LENGTH_OFFSET) = \ *((u32 *)InstancePtr + XBD_LENGTH_OFFSET); \ *((u32 *)DestinationPtr + XBD_STATUS_OFFSET) = \ *((u32 *)InstancePtr + XBD_STATUS_OFFSET); \ *((u32 *)DestinationPtr + XBD_DEVICE_STATUS_OFFSET) = \ *((u32 *)InstancePtr + XBD_DEVICE_STATUS_OFFSET); \ *((u32 *)DestinationPtr + XBD_ID_OFFSET) = \ *((u32 *)InstancePtr + XBD_ID_OFFSET); \ *((u32 *)DestinationPtr + XBD_FLAGS_OFFSET) = \ *((u32 *)InstancePtr + XBD_FLAGS_OFFSET); \ *((u32 *)DestinationPtr + XBD_RQSTED_LENGTH_OFFSET) = \ *((u32 *)InstancePtr + XBD_RQSTED_LENGTH_OFFSET); \ } /************************** Variable Definitions *****************************/ /************************** Function Prototypes ******************************/ /****************************************************************************** * * FUNCTION: * * XDmaChannel_SgStart * * DESCRIPTION: * * This function starts a scatter gather operation for a scatter gather * DMA channel. The first buffer descriptor in the buffer descriptor list * will be started with the scatter gather operation. A scatter gather list * should have previously been created for the DMA channel and buffer * descriptors put into the scatter gather list such that there are scatter * operations ready to be performed. * * 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: * * A status containing XST_SUCCESS if scatter gather was started successfully * for the DMA channel. * * A value of XST_DMA_SG_NO_LIST indicates the scatter gather list has not * been created. * * A value of XST_DMA_SG_LIST_EMPTY indicates scatter gather was not started * because the scatter gather list of the DMA channel does not contain any * buffer descriptors that are ready to be processed by the hardware. * * A value of XST_DMA_SG_IS_STARTED indicates scatter gather was not started * because the scatter gather was not stopped, but was already started. * * A value of XST_DMA_SG_BD_NOT_COMMITTED indicates the buffer descriptor of * scatter gather list which was to be started is not committed to the list. * This status is more likely if this function is being called from an ISR * and non-ISR processing is putting descriptors into the list. * * A value of XST_DMA_SG_NO_DATA indicates that the buffer descriptor of the * scatter gather list which was to be started had already been used by the * hardware for a DMA transfer that has been completed. * * NOTES: * * It is the responsibility of the caller to get all the buffer descriptors * after performing a stop operation and before performing a start operation. * If buffer descriptors are not retrieved between stop and start operations, * buffer descriptors may be processed by the hardware more than once. * ******************************************************************************/ XStatus XDmaChannel_SgStart(XDmaChannel * InstancePtr) { u32 Register; XBufDescriptor *LastDescriptorPtr; /* assert to verify input arguments */ XASSERT_NONVOID(InstancePtr != 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 scatter gather list exists but is empty then return a status */ if (XDmaChannel_IsSgListEmpty(InstancePtr)) { return XST_DMA_SG_LIST_EMPTY; } /* if scatter gather is busy for the DMA channel, return a status because * restarting it could lose data */ Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_DMAS_REG_OFFSET); if (Register & XDC_DMASR_SG_BUSY_MASK) { return XST_DMA_SG_IS_STARTED; } /* get the address of the last buffer descriptor which the DMA hardware * finished processing */ LastDescriptorPtr = (XBufDescriptor *) XIo_In32(InstancePtr->RegBaseAddress + XDC_BDA_REG_OFFSET); /* setup the first buffer descriptor that will be sent when the scatter * gather channel is enabled, this is only necessary one time since * the BDA register of the channel maintains the last buffer descriptor * processed */ if (LastDescriptorPtr == NULL) { XIo_Out32(InstancePtr->RegBaseAddress + XDC_BDA_REG_OFFSET, (u32) InstancePtr->GetPtr); } else { XBufDescriptor *NextDescriptorPtr; /* get the next descriptor to be started, if the status indicates it * hasn't already been used by the h/w, then it's OK to start it, * s/w sets the status of each descriptor to busy and then h/w clears * the busy when it is complete */ NextDescriptorPtr = XBufDescriptor_GetNextPtr(LastDescriptorPtr); if ((XBufDescriptor_GetStatus(NextDescriptorPtr) & XDC_DMASR_BUSY_MASK) == 0) { return XST_DMA_SG_NO_DATA; } /* don't start the DMA SG channel if the descriptor to be processed * by h/w is to be committed by the s/w, this function can be called * such that it interrupts a thread that was putting into the list */ if (NextDescriptorPtr == InstancePtr->CommitPtr) { return XST_DMA_SG_BD_NOT_COMMITTED; } } /* start the scatter gather operation by clearing the stop bit in the * control register and setting the enable bit in the s/w control register, * both of these are necessary to cause it to start, right now the order of * these statements is important, the software control register should be * set 1st. The other order can cause the CPU to have a loss of sync * because it cannot read/write the register while the DMA operation is * running */ Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_SWCR_REG_OFFSET); XIo_Out32(InstancePtr->RegBaseAddress + XDC_SWCR_REG_OFFSET, Register | XDC_SWCR_SG_ENABLE_MASK); Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_DMAC_REG_OFFSET); XIo_Out32(InstancePtr->RegBaseAddress + XDC_DMAC_REG_OFFSET, Register & ~XDC_DMACR_SG_DISABLE_MASK); /* indicate the DMA channel scatter gather operation was started * successfully */ return XST_SUCCESS; } /****************************************************************************** * * FUNCTION: * * XDmaChannel_SgStop * * DESCRIPTION: * * This function stops a scatter gather operation for a scatter gather * DMA channel. This function starts the process of stopping a scatter * gather operation that is in progress and waits for the stop to be completed. * Since it waits for the operation to stopped before returning, this function * could take an amount of time relative to the size of the DMA scatter gather * operation which is in progress. The scatter gather list of the DMA channel * is not modified by this function such that starting the scatter gather * channel after stopping it will cause it to resume. This operation is * considered to be a graceful stop in that the scatter gather operation * completes the current buffer descriptor before stopping. * * If the interrupt is enabled, an interrupt will be generated when the * operation is stopped and the caller is responsible for handling the * interrupt. * * 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. * * BufDescriptorPtr is also a return value which contains a pointer to the * buffer descriptor which the scatter gather operation completed when it * was stopped. * * RETURN VALUE: * * A status containing XST_SUCCESS if scatter gather was stopped successfully * for the DMA channel. * * A value of XST_DMA_SG_IS_STOPPED indicates scatter gather was not stoppped * because the scatter gather is not started, but was already stopped. * * BufDescriptorPtr contains a pointer to the buffer descriptor which was * completed when the operation was stopped. * * NOTES: * * This function implements a loop which polls the hardware for an infinite * amount of time. If the hardware is not operating correctly, this function * may never return. * ******************************************************************************/ XStatus XDmaChannel_SgStop(XDmaChannel * InstancePtr, XBufDescriptor ** BufDescriptorPtr) { u32 Register; /* assert to verify input arguments */ XASSERT_NONVOID(InstancePtr != NULL); XASSERT_NONVOID(BufDescriptorPtr != NULL); XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY); /* get the contents of the software control register, if scatter gather is not * enabled (started), then return a status because the disable acknowledge * would not be generated */ Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_SWCR_REG_OFFSET); if ((Register & XDC_SWCR_SG_ENABLE_MASK) == 0) { return XST_DMA_SG_IS_STOPPED; } /* Ensure the interrupt status for the scatter gather is cleared such * that this function will wait til the disable has occurred, writing * a 1 to only that bit in the register will clear only it */ XIo_Out32(InstancePtr->RegBaseAddress + XDC_IS_REG_OFFSET, XDC_IXR_SG_DISABLE_ACK_MASK); /* disable scatter gather by writing to the software control register * without modifying any other bits of the register */ XIo_Out32(InstancePtr->RegBaseAddress + XDC_SWCR_REG_OFFSET, Register & ~XDC_SWCR_SG_ENABLE_MASK); /* scatter gather does not disable immediately, but after the current * buffer descriptor is complete, so wait for the DMA channel to indicate * the disable is complete */ do { Register = XIo_In32(InstancePtr->RegBaseAddress + XDC_IS_REG_OFFSET); } while ((Register & XDC_IXR_SG_DISABLE_ACK_MASK) == 0); /* Ensure the interrupt status for the scatter gather disable is cleared, * writing a 1 to only that bit in the register will clear only it */ XIo_Out32(InstancePtr->RegBaseAddress + XDC_IS_REG_OFFSET, XDC_IXR_SG_DISABLE_ACK_MASK); /* set the specified buffer descriptor pointer to point to the buffer * descriptor that the scatter gather DMA channel was processing */ *BufDescriptorPtr = (XBufDescriptor *) XIo_In32(InstancePtr->RegBaseAddress + XDC_BDA_REG_OFFSET); return XST_SUCCESS; } /****************************************************************************** * * FUNCTION: * * XDmaChannel_CreateSgList * * DESCRIPTION: * * This function creates a scatter gather list in the DMA channel. A scatter * gather list consists of a list of buffer descriptors that are available to * be used for scatter gather operations. Buffer descriptors are put into the * list to request a scatter gather operation to be performed. * * A number of buffer descriptors are created from the specified memory and put * into a buffer descriptor list as empty buffer descriptors. This function must * be called before non-empty buffer descriptors may be put into the DMA channel * to request scatter gather operations. * * 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. * * MemoryPtr contains a pointer to the memory which is to be used for buffer * descriptors and must not be cached. * * ByteCount contains the number of bytes for the specified memory to be used * for buffer descriptors. * * RETURN VALUE: * * A status contains XST_SUCCESS if the scatter gather list was successfully * created. * * A value of XST_DMA_SG_LIST_EXISTS indicates that the scatter gather list * was not created because the list has already been created. * * NOTES: * * None. * ******************************************************************************/ XStatus XDmaChannel_CreateSgList(XDmaChannel * InstancePtr, u32 * MemoryPtr, u32 ByteCount) { XBufDescriptor *BufferDescriptorPtr = (XBufDescriptor *) MemoryPtr; XBufDescriptor *PreviousDescriptorPtr = NULL; XBufDescriptor *StartOfListPtr = BufferDescriptorPtr; u32 UsedByteCount; /* assert to verify valid input arguments, alignment for those * arguments that have alignment restrictions, and at least enough * memory for one buffer descriptor */ XASSERT_NONVOID(InstancePtr != NULL); XASSERT_NONVOID(MemoryPtr != NULL); XASSERT_NONVOID(((u32) MemoryPtr & 3) == 0); XASSERT_NONVOID(ByteCount != 0); XASSERT_NONVOID(ByteCount >= sizeof (XBufDescriptor)); XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY); /* if the scatter gather list has already been created, then return * with a status */ if (InstancePtr->TotalDescriptorCount != 0) { return XST_DMA_SG_LIST_EXISTS; } /* loop thru the specified memory block and create as many buffer * descriptors as possible putting each into the list which is * implemented as a ring buffer, make sure not to use any memory which * is not large enough for a complete buffer descriptor */ UsedByteCount = 0; while ((UsedByteCount + sizeof (XBufDescriptor)) <= ByteCount) { /* setup a pointer to the next buffer descriptor in the memory and * update # of used bytes to know when all of memory is used */ BufferDescriptorPtr = (XBufDescriptor *) ((u32) MemoryPtr + UsedByteCount); /* initialize the new buffer descriptor such that it doesn't contain * garbage which could be used by the DMA hardware */ XBufDescriptor_Initialize(BufferDescriptorPtr); /* if this is not the first buffer descriptor to be created, * then link it to the last created buffer descriptor */ if (PreviousDescriptorPtr != NULL) { XBufDescriptor_SetNextPtr(PreviousDescriptorPtr, BufferDescriptorPtr); } /* always keep a pointer to the last created buffer descriptor such * that they can be linked together in the ring buffer */ PreviousDescriptorPtr = BufferDescriptorPtr; /* keep a count of the number of descriptors in the list to allow * error processing to be performed */ InstancePtr->TotalDescriptorCount++; UsedByteCount += sizeof (XBufDescriptor); } /* connect the last buffer descriptor created and inserted in the list * to the first such that a ring buffer is created */ XBufDescriptor_SetNextPtr(BufferDescriptorPtr, StartOfListPtr); /* initialize the ring buffer to indicate that there are no * buffer descriptors in the list which point to valid data buffers */ InstancePtr->PutPtr = BufferDescriptorPtr; InstancePtr->GetPtr = BufferDescriptorPtr; InstancePtr->CommitPtr = NULL; InstancePtr->LastPtr = BufferDescriptorPtr; InstancePtr->ActiveDescriptorCount = 0; /* indicate the scatter gather list was successfully created */ return XST_SUCCESS; } /****************************************************************************** * * FUNCTION: * * XDmaChannel_IsSgListEmpty * * DESCRIPTION: * * This function determines if the scatter gather list of a DMA channel is * empty with regard to buffer descriptors which are pointing to buffers to be * used for scatter gather operations. * * 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: * * A value of TRUE if the scatter gather list is empty, otherwise a value of * FALSE. * * NOTES: * * None. * ******************************************************************************/ u32 XDmaChannel_IsSgListEmpty(XDmaChannel * InstancePtr) { /* assert to verify valid input arguments */ XASSERT_NONVOID(InstancePtr != NULL); XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY); /* if the number of descriptors which are being used in the list is zero * then the list is empty */ return (InstancePtr->ActiveDescriptorCount == 0); } /****************************************************************************** * * FUNCTION: * * XDmaChannel_PutDescriptor * * DESCRIPTION: * * This function puts a buffer descriptor into the DMA channel scatter * gather list. A DMA channel maintains a list of buffer descriptors which are * to be processed. This function puts the specified buffer descriptor * at the next location in the list. Note that since the list is already intact, * the information in the parameter is copied into the list (rather than modify * list pointers on the fly). * * After buffer descriptors are put into the list, they must also be committed * by calling another function. This allows multiple buffer descriptors which * span a single packet to be put into the list while preventing the hardware * from starting the first buffer descriptor of the packet. * * 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. * * BufferDescriptorPtr is a pointer to the buffer descriptor to be put into * the next available location of the scatter gather list. * * RETURN VALUE: * * A status which indicates XST_SUCCESS if the buffer descriptor was * successfully put into the scatter gather list. * * A value of XST_DMA_SG_NO_LIST indicates the scatter gather list has not * been created. * * A value of XST_DMA_SG_LIST_FULL indicates the buffer descriptor was not * put into the list because the list was full. * * A value of XST_DMA_SG_BD_LOCKED indicates the buffer descriptor was not * put into the list because the buffer descriptor in the list which is to * be overwritten was locked. A locked buffer descriptor indicates the higher * layered software is still using the buffer descriptor. * * NOTES: * * It is necessary to create a scatter gather list for a DMA channel before * putting buffer descriptors into it. * ******************************************************************************/ XStatus XDmaChannel_PutDescriptor(XDmaChannel * InstancePtr, XBufDescriptor * BufferDescriptorPtr) { u32 Control; /* assert to verify valid input arguments and alignment for those * arguments that have alignment restrictions */ XASSERT_NONVOID(InstancePtr != NULL); XASSERT_NONVOID(BufferDescriptorPtr != NULL); XASSERT_NONVOID(((u32) BufferDescriptorPtr & 3) == 0); 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 list is full because all descriptors are pointing to valid * buffers, then indicate an error, this code assumes no list or an * empty list is detected above */ if (InstancePtr->ActiveDescriptorCount == InstancePtr->TotalDescriptorCount) { return XST_DMA_SG_LIST_FULL; } /* if the buffer descriptor in the list which is to be overwritten is * locked, then don't overwrite it and return a status */ if (XBufDescriptor_IsLocked(InstancePtr->PutPtr)) { return XST_DMA_SG_BD_LOCKED; } /* set the scatter gather stop bit in the control word of the descriptor * to cause the h/w to stop after it processes this descriptor since it * will be the last in the list */ Control = XBufDescriptor_GetControl(BufferDescriptorPtr); XBufDescriptor_SetControl(BufferDescriptorPtr, Control | XDC_DMACR_SG_DISABLE_MASK); /* set both statuses in the descriptor so we tell if they are updated with * the status of the transfer, the hardware should change the busy in the * DMA status to be false when it completes */ XBufDescriptor_SetStatus(BufferDescriptorPtr, XDC_DMASR_BUSY_MASK); XBufDescriptor_SetDeviceStatus(BufferDescriptorPtr, 0); /* copy the descriptor into the next position in the list so it's ready to * be used by the h/w, this assumes the descriptor in the list prior to this * one still has the stop bit in the control word set such that the h/w * use this one yet */ CopyBufferDescriptor(BufferDescriptorPtr, InstancePtr->PutPtr); /* only the last in the list and the one to be committed have scatter gather * disabled in the control word, a commit requires only one descriptor * to be changed, when # of descriptors to commit > 2 all others except the * 1st and last have scatter gather enabled */ if ((InstancePtr->CommitPtr != InstancePtr->LastPtr) && (InstancePtr->CommitPtr != NULL)) { Control = XBufDescriptor_GetControl(InstancePtr->LastPtr); XBufDescriptor_SetControl(InstancePtr->LastPtr, Control & ~XDC_DMACR_SG_DISABLE_MASK); } /* update the list data based upon putting a descriptor into the list, * these operations must be last */ InstancePtr->ActiveDescriptorCount++; /* only update the commit pointer if it is not already active, this allows * it to be deactivated after every commit such that a single descriptor * which is committed does not appear to be waiting to be committed */ if (InstancePtr->CommitPtr == NULL) { InstancePtr->CommitPtr = InstancePtr->LastPtr; } /* these updates MUST BE LAST after the commit pointer update in order for * the commit pointer to track the correct descriptor to be committed */ InstancePtr->LastPtr = InstancePtr->PutPtr; InstancePtr->PutPtr = XBufDescriptor_GetNextPtr(InstancePtr->PutPtr); return XST_SUCCESS; } /****************************************************************************** * * FUNCTION: * * XDmaChannel_CommitPuts * * DESCRIPTION: * * This function commits the buffer descriptors which have been put into the * scatter list for the DMA channel since the last commit operation was * performed. This enables the calling functions to put several buffer * descriptors into the list (e.g.,a packet's worth) before allowing the scatter * gather operations to start. This prevents the DMA channel hardware from * starting to use the buffer descriptors in the list before they are ready * to be used (multiple buffer descriptors for a single packet). * * 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: * * A status indicating XST_SUCCESS if the buffer descriptors of the list were * successfully committed. * * A value of XST_DMA_SG_NOTHING_TO_COMMIT indicates that the buffer descriptors * were not committed because there was nothing to commit in the list. All the * buffer descriptors which are in the list are commited. * * NOTES: * * None. * ******************************************************************************/ XStatus XDmaChannel_CommitPuts(XDmaChannel * InstancePtr) { /* assert to verify input arguments */ XASSERT_NONVOID(InstancePtr != NULL); XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY); /* if the buffer descriptor to be committed is already committed or * the list is empty (none have been put in), then indicate an error */ if ((InstancePtr->CommitPtr == NULL) || XDmaChannel_IsSgListEmpty(InstancePtr)) { return XST_DMA_SG_NOTHING_TO_COMMIT; } /* last descriptor in the list must have scatter gather disabled so the end * of the list is hit by h/w, if descriptor to commit is not last in list, * commit descriptors by enabling scatter gather in the descriptor */ if (InstancePtr->CommitPtr != InstancePtr->LastPtr) { u32 Control; Control = XBufDescriptor_GetControl(InstancePtr->CommitPtr); XBufDescriptor_SetControl(InstancePtr->CommitPtr, Control & ~XDC_DMACR_SG_DISABLE_MASK); } /* Update the commit pointer to indicate that there is nothing to be * committed, this state is used by start processing to know that the * buffer descriptor to start is not waiting to be committed */ InstancePtr->CommitPtr = NULL; return XST_SUCCESS; } /****************************************************************************** * * FUNCTION: * * XDmaChannel_GetDescriptor * * DESCRIPTION: * * This function gets a buffer descriptor from the scatter gather list of the * DMA channel. The buffer descriptor is retrieved from the scatter gather list * and the scatter gather list is updated to not include the retrieved buffer * descriptor. This is typically done after a scatter gather operation * completes indicating that a data buffer has been successfully sent or data * has been received into the data buffer. The purpose of this function is to * allow the device using the scatter gather operation to get the results of the * operation. * * 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. * * BufDescriptorPtr is a pointer to a pointer to the buffer descriptor which * was retrieved from the list. The buffer descriptor is not really removed * from the list, but it is changed to a state such that the hardware will not * use it again until it is put into the scatter gather list of the DMA channel. * * RETURN VALUE: * * A status indicating XST_SUCCESS if a buffer descriptor was retrieved from * the scatter gather list of the DMA channel. * * A value of XST_DMA_SG_NO_LIST indicates the scatter gather list has not * been created. * * A value of XST_DMA_SG_LIST_EMPTY indicates no buffer descriptor was * retrieved from the list because there are no buffer descriptors to be * processed in the list. * * BufDescriptorPtr is updated to point to the buffer descriptor which was * retrieved from the list if the status indicates success. * * NOTES: * * None. * ******************************************************************************/ XStatus XDmaChannel_GetDescriptor(XDmaChannel * InstancePtr, XBufDescriptor ** BufDescriptorPtr) { u32 Control; /* assert to verify input arguments */ XASSERT_NONVOID(InstancePtr != NULL); 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); }