OEMCacheRangeFlush (Windows Embedded CE 6.0)

1/5/2010

This function is used by the kernel to flush or invalidate a certain range of the cache or translation look-aside buffer (TLB). OEMs must implement this function in the OAL.

Syntax

void OEMCacheRangeFlush(
  LPVOID pAddr,
  DWORD dwLength,
  DWORD dwFlags 
);

Parameters

• pAddr
  [in] Starting virtual address where the cache operation is to be performed. The cache operation is specified by the value in the dwFlags parameter.

• dwLength
  [in] Specifies the length, in bytes.

• dwFlags
  [in] Specifies the operations to be performed.

  You can specify the following values for the dwFlags parameter.

  Value	Description
  CACHE_SYNC_WRITEBACK	Write back cached data.
  CACHE_SYNC_DISCARD	Write back and discard cached data.
  CACHE_SYNC_INSTRUCTIONS	Discard all cached instructions.
  CACHE_SYNC_FLUSH_I_TLB	Flush the instruction TLB.
  CACHE_SYNC_FLUSH_D_TLB	Flush the data TLB.
  CACHE_SYNC_FLUSH_TLB	Flush both the instruction and data TLBs.
  CACHE_SYNC_L2_WRITEBACK	Write back the L2 cache.
  CACHE_SYNC_L2_DISCARD	Write back and discard the L2 cache.
  CACHE_SYNC_ALL	Perform all of the above operations.

Return Value

None.

Remarks

This function replaces calls to FlushDCache, FlushICache, and TLBClear in Windows CE .NET 4.2 and later.

pAddr=NULL and dwLength=0 is a special case, which means all addresses.

For example, the call OEMCacheRangeFlush(NULL, 0, CACHE_SYNC_FLUSH_TLB) flushes the data in the TLB. OEMCacheRangeFlush(NULL, 0, CACHE_SYNC_DISCARD) writes back and discards everything in the data cache.

Operations can also be combined. For example, the call OEMCacheRangeFlush(NULL, 0, CACHE_SYNC_FLUSH_TLB | CACHE_SYNC_DISCARD | CACHE_SYNC_INSTRUCTIONS) writes back and discards the entire data cache, invalidates the entire instruction cache, and flushes the instruction and data TLBs.

If the memory management unit (MMU) supports probing, the special case where dwLength==PAGE_SIZE might be useful because it is commonly used when paging code.

In general, if you are implementing this function you should perform TLB flushes at the end of the function. For example, if dwFlags==(CACHE_SYNC_DISCARD|CACHE_SYNC_FLUSH_TLB), the cache discard operation is usually performed before the TLB flush.

In Windows Embedded CE 6.0, flushing the L1 cache does not flush the L2 cache.

Requirements

See Also

Reference

Required OAL Functions
FlushDCache
FlushICache
TLBClear

Concepts

Cache Flush Routines

Other Resources

CacheRangeFlush