From: gregkh@linuxfoundation•org (Greg KH)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH] Documentation: devicetree: add description for generic bus properties
Date: Thu, 28 Nov 2013 11:10:30 -0800 [thread overview]
Message-ID: <20131128191030.GA2385@kroah.com> (raw)
In-Reply-To: <20131128102845.GB21354@mudshark.cambridge.arm.com>
On Thu, Nov 28, 2013 at 10:28:45AM +0000, Will Deacon wrote:
> Hi Greg,
>
> On Wed, Nov 27, 2013 at 11:06:50PM +0000, Greg KH wrote:
> > On Wed, Nov 27, 2013 at 05:28:06PM +0000, Dave Martin wrote:
> > > >From will.deacon at arm.com Wed Nov 20 12:06:22 2013
> > > A number of discussion points remain to be resolved:
> > >
> > > - Use of the ranges property and describing slave vs master bus
> > > address ranges. In the latter case, we actually want to describe our
> > > address space with respect to the bus on which the bus masters,
> > > rather than the parent. This could potentially be achieved by adding
> > > properties such as dma-parent and dma-ranges (already used by PPC?)
> > >
> > > - Describing masters that master through multiple different buses
> > >
> > > - How on Earth this fits in with the Linux device model (it doesn't)
> >
> > How does this _not_ fit into the Linux device model? What am I missing
> > here that precludes the use of the "driver/device/bus" model we have
> > today?
>
> The main problem is that we have devices which slave on one bus and master
> on another. That then complicates probing, power-management, IOMMU
> configuration, address mapping (e.g. I walk the slave buses to figure out
> where the slave registers live, but then I need a way to work out where
> exactly I master on a different bus) and dynamic coherency, amongst other
> things.
>
> If we try to use the current infrastructure then we end up with one bus per
> device, which usually ends up being a fake bus representing both the slave
> and master buses (which is how the platform bus gets abused) and then device
> drivers having their own idea of the system topology where it's required.
> This is fairly horrible and doesn't work for anything other than the trivial
> case, where one or both of the buses are `dumb' and don't require any work
> from Linux.
Then just put everything on a single "bus", there's nothing in the
driver core that requires a bus to work in a specific way.
> > > .../devicetree/bindings/arm/coherent-bus.txt | 110 +++++++++++++++++++++
> >
> > Why "arm"?
> >
> > What makes it ARM specific?
>
> This is just an RFC, so I'd be happy to put the binding somewhere more
> broad. I'm not sure how much of an issue this is outside of the SoC space,
> though.
There aren't "SoC"s on other architectures? :)
thanks,
greg k-h
next prev parent reply other threads:[~2013-11-28 19:10 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-27 17:28 [RFC PATCH] Documentation: devicetree: add description for generic bus properties Dave Martin
2013-11-27 23:06 ` Greg KH
2013-11-28 10:28 ` Will Deacon
2013-11-28 17:33 ` Dave Martin
2013-11-28 19:13 ` Greg KH
2013-11-28 19:39 ` Dave Martin
2013-11-28 21:25 ` Greg KH
2013-11-29 11:44 ` Will Deacon
2013-11-29 17:37 ` Greg KH
2013-11-29 18:01 ` Will Deacon
2013-11-29 18:11 ` Greg KH
2013-11-29 18:15 ` Will Deacon
2013-11-28 19:10 ` Greg KH [this message]
2013-11-28 20:33 ` Thierry Reding
2013-11-28 21:10 ` Jason Gunthorpe
2013-11-28 22:22 ` Thierry Reding
2013-11-28 23:31 ` Jason Gunthorpe
2013-11-29 2:35 ` Greg KH
2013-11-29 9:37 ` Thierry Reding
2013-11-29 9:57 ` Russell King - ARM Linux
2013-11-29 10:43 ` Thierry Reding
2013-11-29 13:13 ` Dave Martin
2013-11-29 13:29 ` Russell King - ARM Linux
2013-11-29 17:43 ` Greg KH
2013-11-29 17:42 ` Greg KH
2013-11-29 19:45 ` Thierry Reding
2013-12-04 18:43 ` Mark Brown
2013-12-04 19:03 ` Greg KH
2013-12-04 20:27 ` Mark Brown
2013-11-29 9:57 ` Thierry Reding
2013-11-29 14:13 ` Dave Martin
2013-11-29 11:58 ` Dave Martin
2013-11-29 18:43 ` Jason Gunthorpe
2013-12-02 20:25 ` Dave Martin
2013-12-03 0:07 ` Jason Gunthorpe
2013-12-03 11:45 ` Dave Martin
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