On Tue, 3 Dec 2019 01:18:24 -0800 Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > On Tue, Dec 03, 2019 at 09:05:23AM +0000, Jisheng Zhang wrote: > > > > > > > > eg. drivers/mmc/host/sdhci-of-dwcmshc.c > > > > > > > Thanks for the suggestion! Christoph's suggestion can prevent the the issue > > > from the block layer, thus the code can be shared across all > > > > To be honest, I did consider similar solution from block layer, I.E set > > the seg_boundary_mask, when submitting the workaround last year, but per > > my understanding, SDHCI limitation is the physical DMA addr can't span one > > specific boundary, > > As in exactly one boundary and not an alignment? Where the one > boundary is not a power of two and thus can't be expressed? Take drivers/mmc/host/sdhci-of-dwcmshc.c for example, target physical DMA addr can't span 128MB, 256MB, 128*3MB, ...128*nMB I'm not sure whether blk_queue_segment_boundary could solve this limitation. > > > > so setting seg_boundary_mask w/ blk_queue_segment_boundary > > can't work. I'm not sure I understand blk_queue_segment_boundary() properly. > > May Christoph help to clarify? > > > > From another side, drivers/ata/libata-sff.c also workaround the 64K phy DMA > > boundary limitation itself rather than from block layer. > > As far as I can tell that workaround should use the segment boundary > setting as well.
