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    SubjectRe: [RFC PATCH 08/13] mmc: omap_hsmmc: limit max_segs with the EDMA DMAC
    On Fri, Sep 21, 2012 at 10:48 PM, Felipe Balbi <balbi@ti.com> wrote:
    > On Fri, Sep 21, 2012 at 10:47:30PM +0530, S, Venkatraman wrote:
    >> On Fri, Sep 21, 2012 at 10:45 PM, S, Venkatraman <svenkatr@ti.com> wrote:
    >> > On Thu, Sep 20, 2012 at 8:13 PM, Matt Porter <mporter@ti.com> wrote:
    >> >> The EDMA DMAC has a hardware limitation that prevents supporting
    >> >> scatter gather lists with any number of segments. Since the EDMA
    >> >> DMA Engine driver sets the maximum segments to 16, we do the
    >> >> same.
    >> >>
    >> >> Note: this can be removed once the DMA Engine API supports an
    >> >> API to query the DMAC's segment limitations.
    >> >>
    >> >
    >> > I wouldn't want to bind the properties of EDMA to omap_hsmmc as this patch
    >> > suggests. Why don't we have a max_segs property, which when explicitly specified
    >> > in DT, will override the default ?
    >>
    >> If you are adventurous, this can be a generic mmc DT binding instead
    >> of restricting it to OMAP.
    >
    > I say if it's a limitation in the DMAC, then DMAC's driver should handle
    > it, no ? Meaning that in this case you would copy from one multi-segment
    > sg into a one-segment sg and when transfer is complete, before calling
    > user's callback, copy data the other way around (?)
    >

    Right ! So even if the property is defined for MMC, Matt will end up coding the
    limitation into every peripheral driver that uses EMAC, which doesn't scale.
    Your solution is better.


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