Re: DMA and Cache coherency on machines without hardware enforced

Jes Sorensen (Jes.Sorensen@cern.ch)
02 Dec 1999 14:05:49 +0100


>>>>> "Ingo" == Ingo Molnar <mingo@chiara.csoma.elte.hu> writes:

Ingo> On Wed, 1 Dec 1999, Pete Zaitcev wrote:

>> >page = __get_free_pages(whatever, order); >ptr =
>> ioremap_nocache(virt_to_phys(page), 1 << (order+PAGE_SHIFT));
>>
>> When was ioremap_nocache() introduced and was it sprinked with a
>> penguin pee?

Ingo> well, 2 or 3 years ago, in the late 2.0 kernels.

I still see a need for a get_free_coherent_page() for use in cases
where you want to share physical memory with devices. On coherent
architectures get_free_page() does just fine today, but on machines
like the m68k it does not. Having a standard interface would making
device drivers portable a lot easier.

Question is which API would be the most appropriate.

Jes

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