Messages in this thread |  | | From | Paul Mackerras <> | Date | Thu, 12 Sep 2002 16:12:56 +1000 (EST) | Subject | Re: [PATCH] highmem I/O for ide-pmac.c |
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Jens Axboe writes:
> Doesn't look like it's needed at all, at least you never turn on highmem > I/O with ide_toggle_bounce() :-)
Foo, neither I do. :(
> BTW, it would be ok to export that from ide-dma.c instead of duplicating > it in ide-pmac.
Looking at it again, both ide_build_sglist and ide_raw_build_sglist do *almost* what we want. If ide-pmac used hwif->sg_table instead of pmif->sg_table, and if ide_[raw_]build_sglist were exported and took the maximum number of entries as a parameter instead of using the PRD_ENTRIES constant, then ide-pmac wouldn't need to have its own versions of those routines. Would those changes be OK?
Ben, any reason why we have to use pmif->sg_table rather than hwif->sg_table?
> Also, can you grow sg segments indefinitely?
Each DBDMA (descriptor-based DMA) command has a 16-byte length field, so is limited to 65535 bytes. There is code in pmac_ide_build_dmatable to create multiple DBDMA commands from a single scatterlist element if necessary. We should limit the lengths of the segments instead, then we could have a 1-1 correspondence of scatterlist elements to DBDMA command blocks.
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