Thread (52 messages) 52 messages, 9 authors, 2012-10-09

Re: [RFC PATCH 08/13] mmc: omap_hsmmc: limit max_segs with the EDMA DMAC

From: Vinod Koul <hidden>
Date: 2012-09-27 09:47:09
Also in: linux-arm-kernel, linux-mmc, linux-omap, linux-spi, lkml

On Fri, 2012-09-21 at 19:47 +0100, Russell King - ARM Linux wrote:
On Fri, Sep 21, 2012 at 10:45:29PM +0530, S, Venkatraman 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 ?
Why not have a generic way that DMA engine can export these kinds of
properties?
We discussed this at KS. I was of opinion that  DMA engine should export
controller and channel capabilities as part of the channel it returns.

Some folks had an opinion that they already know how to use controller
so may not be very helpful, but if it is going to help (which I think),
i have a patch for this :)


-- 
~Vinod
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