On Tue, Nov 04 2014, Gregory Fong wrote: > The alignment in cma_alloc() is done w.r.t. the bitmap. This is a > problem when, for example: > > - a device requires 16M (order 12) alignment > - the CMA region is not 16 M aligned > > In such a case, can result with the CMA region starting at, say, > 0x2f800000 but any allocation you make from there will be aligned from > there. Requesting an allocation of 32 M with 16 M alignment, will > result in an allocation from 0x2f800000 to 0x31800000, which doesn't > work very well if your strange device requires 16M alignment. > > This doesn't have the behavior I would expect, which would be for the > allocation to be aligned w.r.t. the start of memory. I realize that > aligning the CMA region is an option, but don't see why cma_alloc() > aligns to the start of the CMA region. Is there a good reason for > having cma_alloc() alignment work this way?
No, it's a bug. The alignment should indicate alignment of physical address not position in CMA region. -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +--<m...@google.com>--<xmpp:min...@jabber.org>--ooO--(_)--Ooo-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
