cvs commit: src/sys/alpha/alpha busdma_machdep.c

Scott Long scottl at
Thu Sep 15 12:15:05 PDT 2005

John Baldwin wrote:
> On Thursday 15 September 2005 01:09 pm, John Baldwin wrote:
>>jhb         2005-09-15 17:09:42 UTC
>>  FreeBSD src repository
>>  Modified files:
>>    sys/alpha/alpha      busdma_machdep.c
>>  Log:
>>  Add a memory barrier for PREWRITE operations to ensure all writes by the
>>  CPU have drained before further writes to kick off the operation.
> Other architectures with relaxed memory ordering probably also need thus such 
> as ia64, powerpc, and perhaps amd64.  sparc64 already has a barrier.  BTW, it 
> seems that the bus_dma code could be somewhat simplified if there was a 
> sys/kern/subr_busdma.c that contained routines to implement bounce buffers 
> that could be used by the MD code since the MD code that does do bounce pages 
> tends to duplicate a lot of stuff between the different archs.

Indeed it does, and if you want to work on it, please feel free to send 
it to me for


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