On Fri, Sep 21, 2012 at 10:48 PM, Felipe Balbi [off-list ref] wrote:

On Fri, Sep 21, 2012 at 10:47:30PM +0530, S, Venkatraman wrote:

quoted

On Fri, Sep 21, 2012 at 10:45 PM, S, Venkatraman [off-list ref] wrote:

quoted

On Thu, Sep 20, 2012 at 8:13 PM, Matt Porter [off-list ref] wrote:

quoted

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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