path: root/drivers/staging/hv/RingBuffer.c

/*
 *
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * 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., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 *
 */


#include "include/logging.h"
#include "RingBuffer.h"

//
// #defines
//

// Amount of space to write to
#define BYTES_AVAIL_TO_WRITE(r, w, z) ((w) >= (r))?((z) - ((w) - (r))):((r) - (w))


/*++

Name:
	GetRingBufferAvailBytes()

Description:
	Get number of bytes available to read and to write to
	for the specified ring buffer

--*/
static inline void
GetRingBufferAvailBytes(RING_BUFFER_INFO *rbi, UINT32 *read, UINT32 *write)
{
	UINT32 read_loc,write_loc;

	// Capture the read/write indices before they changed
	read_loc = rbi->RingBuffer->ReadIndex;
	write_loc = rbi->RingBuffer->WriteIndex;

	*write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->RingDataSize);
	*read = rbi->RingDataSize - *write;
}

/*++

Name:
	GetNextWriteLocation()

Description:
	Get the next write location for the specified ring buffer

--*/
static inline UINT32
GetNextWriteLocation(RING_BUFFER_INFO* RingInfo)
{
	UINT32 next = RingInfo->RingBuffer->WriteIndex;

	ASSERT(next < RingInfo->RingDataSize);

	return next;
}

/*++

Name:
	SetNextWriteLocation()

Description:
	Set the next write location for the specified ring buffer

--*/
static inline void
SetNextWriteLocation(RING_BUFFER_INFO* RingInfo, UINT32 NextWriteLocation)
{
	RingInfo->RingBuffer->WriteIndex = NextWriteLocation;
}

/*++

Name:
	GetNextReadLocation()

Description:
	Get the next read location for the specified ring buffer

--*/
static inline UINT32
GetNextReadLocation(RING_BUFFER_INFO* RingInfo)
{
	UINT32 next = RingInfo->RingBuffer->ReadIndex;

	ASSERT(next < RingInfo->RingDataSize);

	return next;
}

/*++

Name:
	GetNextReadLocationWithOffset()

Description:
	Get the next read location + offset for the specified ring buffer.
	This allows the caller to skip

--*/
static inline UINT32
GetNextReadLocationWithOffset(RING_BUFFER_INFO* RingInfo, UINT32 Offset)
{
	UINT32 next = RingInfo->RingBuffer->ReadIndex;

	ASSERT(next < RingInfo->RingDataSize);
	next += Offset;
	next %= RingInfo->RingDataSize;

	return next;
}

/*++

Name:
	SetNextReadLocation()

Description:
	Set the next read location for the specified ring buffer

--*/
static inline void
SetNextReadLocation(RING_BUFFER_INFO* RingInfo, UINT32 NextReadLocation)
{
	RingInfo->RingBuffer->ReadIndex = NextReadLocation;
}


/*++

Name:
	GetRingBuffer()

Description:
	Get the start of the ring buffer

--*/
static inline void *
GetRingBuffer(RING_BUFFER_INFO* RingInfo)
{
	return (void *)RingInfo->RingBuffer->Buffer;
}


/*++

Name:
	GetRingBufferSize()

Description:
	Get the size of the ring buffer

--*/
static inline UINT32
GetRingBufferSize(RING_BUFFER_INFO* RingInfo)
{
	return RingInfo->RingDataSize;
}

/*++

Name:
	GetRingBufferIndices()

Description:
	Get the read and write indices as UINT64 of the specified ring buffer

--*/
static inline UINT64
GetRingBufferIndices(RING_BUFFER_INFO* RingInfo)
{
	return ((UINT64)RingInfo->RingBuffer->WriteIndex << 32) || RingInfo->RingBuffer->ReadIndex;
}


/*++

Name:
	DumpRingInfo()

Description:
	Dump out to console the ring buffer info

--*/
void
DumpRingInfo(RING_BUFFER_INFO* RingInfo, char *Prefix)
{
	UINT32 bytesAvailToWrite;
	UINT32 bytesAvailToRead;

	GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);

	DPRINT(VMBUS, DEBUG_RING_LVL, "%s <<ringinfo %p buffer %p avail write %u avail read %u read idx %u write idx %u>>",
		Prefix,
		RingInfo,
		RingInfo->RingBuffer->Buffer,
		bytesAvailToWrite,
		bytesAvailToRead,
		RingInfo->RingBuffer->ReadIndex,
		RingInfo->RingBuffer->WriteIndex);
}

//
// Internal routines
//
static UINT32
CopyToRingBuffer(
	RING_BUFFER_INFO	*RingInfo,
	UINT32				StartWriteOffset,
	void *				Src,
	UINT32				SrcLen);

static UINT32
CopyFromRingBuffer(
	RING_BUFFER_INFO	*RingInfo,
	void *				Dest,
	UINT32				DestLen,
	UINT32				StartReadOffset);



/*++

Name:
	RingBufferGetDebugInfo()

Description:
	Get various debug metrics for the specified ring buffer

--*/
void
RingBufferGetDebugInfo(
	RING_BUFFER_INFO		*RingInfo,
	RING_BUFFER_DEBUG_INFO	*DebugInfo
	)
{
	UINT32 bytesAvailToWrite;
	UINT32 bytesAvailToRead;

	if (RingInfo->RingBuffer)
	{
		GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);

		DebugInfo->BytesAvailToRead = bytesAvailToRead;
		DebugInfo->BytesAvailToWrite = bytesAvailToWrite;
		DebugInfo->CurrentReadIndex = RingInfo->RingBuffer->ReadIndex;
		DebugInfo->CurrentWriteIndex = RingInfo->RingBuffer->WriteIndex;

		DebugInfo->CurrentInterruptMask = RingInfo->RingBuffer->InterruptMask;
	}
}


/*++

Name:
	GetRingBufferInterruptMask()

Description:
	Get the interrupt mask for the specified ring buffer

--*/
UINT32
GetRingBufferInterruptMask(
	RING_BUFFER_INFO *rbi
	)
{
	return rbi->RingBuffer->InterruptMask;
}

/*++

Name:
	RingBufferInit()

Description:
	Initialize the ring buffer

--*/
int
RingBufferInit(
	RING_BUFFER_INFO	*RingInfo,
	void				*Buffer,
	UINT32				BufferLen
	)
{
	ASSERT(sizeof(RING_BUFFER) == PAGE_SIZE);

	memset(RingInfo, 0, sizeof(RING_BUFFER_INFO));

	RingInfo->RingBuffer = (RING_BUFFER*)Buffer;
	RingInfo->RingBuffer->ReadIndex = RingInfo->RingBuffer->WriteIndex = 0;

	RingInfo->RingSize = BufferLen;
	RingInfo->RingDataSize = BufferLen - sizeof(RING_BUFFER);

	RingInfo->RingLock = SpinlockCreate();

	return 0;
}

/*++

Name:
	RingBufferCleanup()

Description:
	Cleanup the ring buffer

--*/
void
RingBufferCleanup(
	RING_BUFFER_INFO* RingInfo
	)
{
	SpinlockClose(RingInfo->RingLock);
}

/*++

Name:
	RingBufferWrite()

Description:
	Write to the ring buffer

--*/
int
RingBufferWrite(
	RING_BUFFER_INFO*	OutRingInfo,
	SG_BUFFER_LIST		SgBuffers[],
	UINT32				SgBufferCount
	)
{
	int i=0;
	UINT32 byteAvailToWrite;
	UINT32 byteAvailToRead;
	UINT32 totalBytesToWrite=0;

	volatile UINT32 nextWriteLocation;
	UINT64 prevIndices=0;

	DPRINT_ENTER(VMBUS);

	for (i=0; i < SgBufferCount; i++)
	{
		totalBytesToWrite += SgBuffers[i].Length;
	}

	totalBytesToWrite += sizeof(UINT64);

	SpinlockAcquire(OutRingInfo->RingLock);

	GetRingBufferAvailBytes(OutRingInfo, &byteAvailToRead, &byteAvailToWrite);

	DPRINT_DBG(VMBUS, "Writing %u bytes...", totalBytesToWrite);

	//DumpRingInfo(OutRingInfo, "BEFORE ");

	// If there is only room for the packet, assume it is full. Otherwise, the next time around, we think the ring buffer
	// is empty since the read index == write index
	if (byteAvailToWrite <= totalBytesToWrite)
	{
		DPRINT_DBG(VMBUS, "No more space left on outbound ring buffer (needed %u, avail %u)", totalBytesToWrite, byteAvailToWrite);

		SpinlockRelease(OutRingInfo->RingLock);

		DPRINT_EXIT(VMBUS);

		return -1;
	}

	// Write to the ring buffer
	nextWriteLocation = GetNextWriteLocation(OutRingInfo);

	for (i=0; i < SgBufferCount; i++)
	{
		 nextWriteLocation = CopyToRingBuffer(OutRingInfo,
												nextWriteLocation,
												SgBuffers[i].Data,
												SgBuffers[i].Length);
	}

	// Set previous packet start
	prevIndices = GetRingBufferIndices(OutRingInfo);

	nextWriteLocation = CopyToRingBuffer(OutRingInfo,
												nextWriteLocation,
												&prevIndices,
												sizeof(UINT64));

	// Make sure we flush all writes before updating the writeIndex
	MemoryFence();

	// Now, update the write location
	SetNextWriteLocation(OutRingInfo, nextWriteLocation);

	//DumpRingInfo(OutRingInfo, "AFTER ");

	SpinlockRelease(OutRingInfo->RingLock);

	DPRINT_EXIT(VMBUS);

	return 0;
}


/*++

Name:
	RingBufferPeek()

Description:
	Read without advancing the read index

--*/
int
RingBufferPeek(
	RING_BUFFER_INFO*	InRingInfo,
	void*				Buffer,
	UINT32				BufferLen
	)
{
	UINT32 bytesAvailToWrite;
	UINT32 bytesAvailToRead;
	UINT32 nextReadLocation=0;

	SpinlockAcquire(InRingInfo->RingLock);

	GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);

	// Make sure there is something to read
	if (bytesAvailToRead < BufferLen )
	{
		//DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen);

		SpinlockRelease(InRingInfo->RingLock);

		return -1;
	}

	// Convert to byte offset
	nextReadLocation = GetNextReadLocation(InRingInfo);

	nextReadLocation = CopyFromRingBuffer(InRingInfo,
											Buffer,
											BufferLen,
											nextReadLocation);

	SpinlockRelease(InRingInfo->RingLock);

	return 0;
}


/*++

Name:
	RingBufferRead()

Description:
	Read and advance the read index

--*/
int
RingBufferRead(
	RING_BUFFER_INFO*	InRingInfo,
	void *				Buffer,
	UINT32				BufferLen,
	UINT32				Offset
	)
{
	UINT32 bytesAvailToWrite;
	UINT32 bytesAvailToRead;
	UINT32 nextReadLocation=0;
	UINT64 prevIndices=0;

	ASSERT(BufferLen > 0);

	SpinlockAcquire(InRingInfo->RingLock);

	GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);

	DPRINT_DBG(VMBUS, "Reading %u bytes...", BufferLen);

	//DumpRingInfo(InRingInfo, "BEFORE ");

	// Make sure there is something to read
	if (bytesAvailToRead < BufferLen )
	{
		DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen);

		SpinlockRelease(InRingInfo->RingLock);

		return -1;
	}

	nextReadLocation = GetNextReadLocationWithOffset(InRingInfo, Offset);

	nextReadLocation = CopyFromRingBuffer(InRingInfo,
											Buffer,
											BufferLen,
											nextReadLocation);

	nextReadLocation = CopyFromRingBuffer(InRingInfo,
											&prevIndices,
											sizeof(UINT64),
											nextReadLocation);

	// Make sure all reads are done before we update the read index since
	// the writer may start writing to the read area once the read index is updated
	MemoryFence();

	// Update the read index
	SetNextReadLocation(InRingInfo, nextReadLocation);

	//DumpRingInfo(InRingInfo, "AFTER ");

	SpinlockRelease(InRingInfo->RingLock);

	return 0;
}


/*++

Name:
	CopyToRingBuffer()

Description:
	Helper routine to copy from source to ring buffer.
	Assume there is enough room. Handles wrap-around in dest case only!!

--*/
UINT32
CopyToRingBuffer(
	RING_BUFFER_INFO	*RingInfo,
	UINT32				StartWriteOffset,
	void *				Src,
	UINT32				SrcLen)
{
	void * ringBuffer=GetRingBuffer(RingInfo);
	UINT32 ringBufferSize=GetRingBufferSize(RingInfo);
	UINT32 fragLen;

	if (SrcLen > ringBufferSize - StartWriteOffset) // wrap-around detected!
	{
		DPRINT_DBG(VMBUS, "wrap-around detected!");

		fragLen = ringBufferSize - StartWriteOffset;
		memcpy(ringBuffer + StartWriteOffset, Src, fragLen);
		memcpy(ringBuffer, Src + fragLen, SrcLen - fragLen);
	}
	else
	{
		memcpy(ringBuffer + StartWriteOffset, Src, SrcLen);
	}

	StartWriteOffset += SrcLen;
	StartWriteOffset %= ringBufferSize;

	return StartWriteOffset;
}


/*++

Name:
	CopyFromRingBuffer()

Description:
	Helper routine to copy to source from ring buffer.
	Assume there is enough room. Handles wrap-around in src case only!!

--*/
UINT32
CopyFromRingBuffer(
	RING_BUFFER_INFO	*RingInfo,
	void *				Dest,
	UINT32				DestLen,
	UINT32				StartReadOffset)
{
	void * ringBuffer=GetRingBuffer(RingInfo);
	UINT32 ringBufferSize=GetRingBufferSize(RingInfo);

	UINT32 fragLen;

	if (DestLen > ringBufferSize - StartReadOffset) // wrap-around detected at the src
	{
		DPRINT_DBG(VMBUS, "src wrap-around detected!");

		fragLen = ringBufferSize - StartReadOffset;

		memcpy(Dest, ringBuffer + StartReadOffset, fragLen);
		memcpy(Dest + fragLen, ringBuffer, DestLen - fragLen);
	}
	else
	{
		memcpy(Dest, ringBuffer + StartReadOffset, DestLen);
	}

	StartReadOffset += DestLen;
	StartReadOffset %= ringBufferSize;

	return StartReadOffset;
}


// eof