* Inconsistent pgprot between dma_alloc_coherent() and dma_mmap_cohernet()
@ 2014-11-10 14:33 Takashi Iwai
0 siblings, 0 replies; only message in thread
From: Takashi Iwai @ 2014-11-10 14:33 UTC (permalink / raw)
To: linux-mm; +Cc: linux-kernel
Hi,
I noticed using dma_mmap_coherent() on pages allocated via
dma_alloc_coherent() results in a warning on x86:
map pfn RAM range req uncached-minus for [mem 0x21d500000-0x21d51ffff], got write-back
which comes from arch/x86/mm/pat.c.
Looking at the code, it seems that dma_mmap_coherent() blindly assumes
that the pages are with pgprot_noncached(), but on x86, it's obviously
not. Maybe some other archs have the same problem.
How should we fix this? Defining a new pgprot_xxx(), and falling back
to pgprot_noncached if undefined? Or is it just x86 and do it only
there?
thanks,
Takashi
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2014-11-10 14:33 Inconsistent pgprot between dma_alloc_coherent() and dma_mmap_cohernet() Takashi Iwai
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