Messages in this thread | | | Date | Mon, 30 Jul 2018 11:11:33 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH mmc-next v3 3/3] mmc: sdhci-of-dwcmshc: solve 128MB DMA boundary limitation |
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On Mon, 30 Jul 2018 03:11:59 +0000 Matthew Leon <matthewleon@linux.com> wrote:
> >> Hey Jisheng, > > >Hi, > > >> > > >In LKML, we'd better not top post. > > Noted. My apologies. > > >> Shouldn't we be splitting until all DMA blocks are less than 128M > boundary? > >> I am a noob, but I think we should be prepared for boundaries that when > >> split in two, will still be greater than 128M. Feel free to disagree but > >> please explain why I may be wrong. Thank-you. > > >the limitation is "DMA addr can't span 128MB boundary" rather than "must be > >less than 128MB", they are different. > > >And the max transfer size of one DMA desc is 64KB. > > >thanks > > I have misspoken. What if the DMA transfer size is 1024M? If we split in > two, then we have 2 transfers, each of which span 512M. So wouldn't we need > to split again to have 4 transfers, each of which span 128M? >
the max transfer size of each desc is 64KB, how could it be 1024MB?
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