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/*++
Copyright (c) 1991 Microsoft Corporation
Module Name:
j4flshio.c
Abstract:
This module implements the system dependent kernel function to flush
the data cache for I/O transfers on a MIPS R4000 Jazz system.
Author:
David N. Cutler (davec) 24-Apr-1991
Environment:
Kernel mode only.
Revision History:
--*/
#include "halp.h"
VOID
HalFlushIoBuffers (
IN PMDL Mdl,
IN BOOLEAN ReadOperation,
IN BOOLEAN DmaOperation
)
/*++
Routine Description:
This function flushes the I/O buffer specified by the memory descriptor
list from the data cache on the current processor.
Arguments:
Mdl - Supplies a pointer to a memory descriptor list that describes the
I/O buffer location.
ReadOperation - Supplies a boolean value that determines whether the I/O
operation is a read into memory.
DmaOperation - Supplies a boolean value that determines whether the I/O
operation is a DMA operation.
Return Value:
None.
--*/
{
ULONG CacheSegment;
ULONG Length;
ULONG Offset;
KIRQL OldIrql;
PULONG PageFrame;
ULONG Source;
//
// The Jazz R4000 uses a write back data cache and, therefore, must be
// flushed on reads and writes.
//
// If the length of the I/O operation is greater than the size of the
// data cache, then sweep the entire data cache. Otherwise, export or
// purge individual pages from the data cache as appropriate.
//
Offset = Mdl->ByteOffset & PCR->DcacheAlignment;
Length = (Mdl->ByteCount +
PCR->DcacheAlignment + Offset) & ~PCR->DcacheAlignment;
if ((Length > PCR->FirstLevelDcacheSize) &&
(Length > PCR->SecondLevelDcacheSize)) {
//
// If the I/O operation is a DMA operation, or the I/O operation is
// not a DMA operation and the I/O operation is a page read operation,
// then sweep (index/writeback/invalidate) the entire data cache.
//
if ((DmaOperation != FALSE) ||
((DmaOperation == FALSE) &&
(ReadOperation != FALSE) &&
((Mdl->MdlFlags & MDL_IO_PAGE_READ) != 0))) {
HalSweepDcache();
}
//
// If the I/O operation is a page read, then sweep (index/invalidate)
// the entire instruction cache.
//
if ((ReadOperation != FALSE) &&
((Mdl->MdlFlags & MDL_IO_PAGE_READ) != 0)) {
HalSweepIcache();
}
} else {
//
// Export or purge the specified pages from the data cache and
// instruction caches as appropriate.
//
// Compute the number of pages to flush and the starting MDL page
// frame address.
//
Offset = Mdl->ByteOffset & ~PCR->DcacheAlignment;
PageFrame = (PULONG)(Mdl + 1);
Source = ((ULONG)(Mdl->StartVa) & 0xfffff000) | Offset;
//
// Export or purge the specified page segments from the data and
// instruction caches as appropriate.
//
do {
if (Length >= (PAGE_SIZE - Offset)) {
CacheSegment = PAGE_SIZE - Offset;
} else {
CacheSegment = Length;
}
if (ReadOperation == FALSE) {
//
// The I/O operation is a write and the data only needs to
// to be copied back into memory if the operation is also
// a DMA operation.
//
if (DmaOperation != FALSE) {
HalFlushDcachePage((PVOID)Source, *PageFrame, CacheSegment);
}
} else {
//
// If the I/O operation is a DMA operation, then purge the
// data cache. Otherwise, is the I/O operation is a page read
// operation, then export the data cache.
//
if (DmaOperation != FALSE) {
HalPurgeDcachePage((PVOID)Source, *PageFrame, CacheSegment);
} else if ((Mdl->MdlFlags & MDL_IO_PAGE_READ) != 0) {
HalFlushDcachePage((PVOID)Source, *PageFrame, CacheSegment);
}
//
// If the I/O operation is a page read, then the instruction
// cache must be purged.
//
if ((Mdl->MdlFlags & MDL_IO_PAGE_READ) != 0) {
HalPurgeIcachePage((PVOID)Source, *PageFrame, CacheSegment);
}
}
PageFrame += 1;
Length -= CacheSegment;
Offset = 0;
Source += CacheSegment;
} while(Length != 0);
}
return;
}
ULONG
HalGetDmaAlignmentRequirement (
VOID
)
/*++
Routine Description:
This function returns the alignment requirements for DMA transfers on
host system.
Arguments:
None.
Return Value:
The DMA alignment requirement is returned as the fucntion value.
--*/
{
return PCR->DcacheFillSize;
}
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