Messages in this thread | | | From | Grant Likely <> | Subject | Re: [PATCH] of: Support a PCI device that is compatible with 'simple-bus' | Date | Mon, 04 Mar 2013 10:55:36 +0800 |
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On Wed, 19 Dec 2012 12:18:00 -0700, Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote: > On Wed, Dec 19, 2012 at 12:54:51PM +0000, Grant Likely wrote: > > In both cases, the type of transfer is encoded by the BAR address and > > does not get exposed to the child device. Exposing the PCI flags into > > the child bus(es) really isn't a very good idea because they don't make > > sense in that context. It may seem expedient, but it will be fragile. > > Well, it makes as much sense as for a PCI driver - each of the three > transfer types has different coding requirements in the driver, so > each of the three type must be kept separate. > > I haven't looked super closely at this, but the basic desire is to > have IORESOURCE_PREFETCH tagged on the struct resource that reaches > the platform driver. 'get_flags' for a non-PCI addresses scheme always > returns IORESOURCE_MEM, and translating through a ranges doesn't > appear to fix that. This is where 3dw is desirable because it uses a > get_flags that understands the three resource types.
We could possibly change the ranges translation code to pick up IORESOURCE_PREFETCH when a translation crosses a PREFETCH bar. That would also ensure that child nodes don't have to keep the flags field consistent with the ranges mapping.
g.
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