Messages in this thread | | | Subject | Re: [RFC] ARM DMA mapping TODO, v1 | From | Benjamin Herrenschmidt <> | Date | Fri, 29 Apr 2011 07:07:16 +1000 |
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On Thu, 2011-04-28 at 10:30 +0100, Russell King - ARM Linux wrote: > On Thu, Apr 28, 2011 at 07:41:07AM +1000, Benjamin Herrenschmidt wrote: > > > > > As I said above, I don't think bus code can do it. Take my example > > > above of a tulip pci device on x86 and a tulip pci device on ARM. Both > > > use the same PCI code. > > > > > > Maybe something in asm/pci.h - but that invites having lots of bus > > > specific header files in asm/. > > > > > > A better solution imho would be to have an architecture callback for > > > struct device which gets registered, which can inspect the type of > > > the device, and set the flag depending on where it appears in the > > > tree. > > > > Now -that's gross :-) > > > > For PCI you can have the flag propagate from the PHB down, for busses > > without a bus type (platform) then whoever instanciate them (the > > platform code) can set that appropriately. > > How can you do that when it changes mid-bus heirarchy? I'm thinking > of the situation where the DRM stuff is on a child bus below the > root bus, and the root bus has DMA coherent devices on it but the DRM > stuff doesn't.
But that's not PCI right ? IE. with PCI, coherency is a property of the PHB...
> Your solution doesn't allow that - and I believe that's what Arnd is > talking about.
Well, for the rest I'm thinking just bolt it into the platform until you can put the property in the DT :-)
Cheers, Ben.
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