On Thu, Feb 16, 2012 at 05:15:20PM +0000, Catalin Marinas wrote: > On Thu, Feb 16, 2012 at 04:41:02PM +0000, viresh kumar wrote: > > Sorry for starting the long old thread again, but i have to start it as i > > was a bit confused. :( > > > > We know that we can't have multiple mappings with different attributes > > to the same physical memory on ARMv6+ machines due to speculative > > prefetch. > > > > So, we have following kind of mappings in kernel now (please correct me > > if i am wrong): > > - Low Mem: Mapped at boot time to - Normal Cacheable - Bufferable > > - ioremap() - blocked on Low Mem, so that we don't create Device type > > mapping > > to same mem > > - dma_alloc_coherent() and others: > > - Without DMA_MEM_BUFFERABLE selected - gives strongly ordered mem > > (i.e. Non cacheable - Non Bufferable) > > - With DMA_MEM_BUFFERABLE selected - gives Normal - Non cacheable - > > Bufferable mapping > > - Maybe some other too... > > > > I have a doubt with the last mapping mentioned above. We have two > > mappings possibly to the same physical memory, with different > > attributes: One is Cacheable and other one is not. > > > > Is this allowed by ARM? Because the patch in which Russell blocked > > ioremap on Low Mem, he clearly mentioned that these attributes are > > also important and they should be same. > > Section A3.5.7 in the latest ARM ARM (revC) clarifies the mismatched
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