From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 5/6] dma-mapping: support fsl-mc bus
Date: Mon, 5 Mar 2018 19:39:38 +0100
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To: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Cc: mark.rutland-5wv7dgnIgG8@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, stuyoder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, catalin.marinas-5wv7dgnIgG8@public.gmane.org, linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, leoyang.li-3arQi8VN3Tc@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
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On Mon, Mar 05, 2018 at 03:48:32PM +0000, Robin Murphy wrote:
> Unfortunately for us, fsl-mc is conceptually rather like PCI in that it's 
> software-discoverable and the only thing described in DT is the bus "host", 
> thus we need the same sort of thing as for PCI to map from the child 
> devices back to the bus root in order to find the appropriate firmware 
> node. Worse than PCI, though, we wouldn't even have the option of 
> describing child devices statically in firmware at all, since it's actually 
> one of these runtime-configurable "build your own network accelerator" 
> hardware pools where userspace gets to create and destroy "devices" as it 
> likes.

I really hate the PCI special case just as much.  Maybe we just
need a dma_configure method on the bus, and move PCI as well as fsl-mc
to it.