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

John Baldwin jhb at
Thu Sep 15 11:21:03 PDT 2005

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.

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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