Re: [Linux-ia64] Re: 64 Bits DMA Addresses for Alloc Consistent Interfaces.

From: Jeremy Higdon <jeremy_at_sgi.com>
Date: 2003-05-16 17:48:12
On Thu, May 15, 2003 at 07:32:26PM -0700, David S. Miller wrote:
>    From: James Bottomley <James.Bottomley@HansenPartnership.com>
>    Date: 15 May 2003 21:26:14 -0500
>    
>    It was my impression that a CPU cache invalidate cycle relinquishes the
>    cache line (and thus leaves the line free to be owned by the device). 
>    The DMA_TO_DEVICE of dma_sync.. does this, why isn't that sufficient?  I
>    grant that CPU does auto ownership, so if the CPU ever touches the data
>    again the cache line is pulled back in again.
>    
> What flushes the cpu cache after the cpu writes to 'buf'
> so that the device sees what the CPU wrote there?  Consider
> copy-back L2 caches like MIPS has.

Isn't that what dma_cache_wback_inv does?  It flushes cpu cache to memory
so that it is visible to devices.  Is there some additional semantic
desired?

jeremy
Received on Fri May 16 00:52:06 2003

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