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SubjectRe: [PATCH 2/2] drivers/amba: probe via device tree
On Tue, May 24, 2011 at 10:03:35AM -0500, Rob Herring wrote:
> Grant,
>
> On 05/23/2011 10:09 AM, Grant Likely wrote:
> >On Mon, May 23, 2011 at 3:58 AM, Russell King - ARM Linux
> ><linux@arm.linux.org.uk> wrote:
> >>On Mon, May 23, 2011 at 11:37:04AM +0200, Kristoffer Glembo wrote:
> >>>Grant Likely wrote:
> >>>>In the case we're talking about the bus really is an AMBA bus, and all
> >>>>the devices on it are in some sense real amba devices. The problem is
> >>>>that not all of the devices on the bus implement peripheral ID
> >>>>registers or other mechanisms that good upstanding AMBA devices are
> >>>>expected to have.
> >>>
> >>>Before we go hardware bashing of non primecell AMBA devices I would just
> >>>want to point out that the primecell stuff is not part of the AMBA
> >>>specification.
> >>
> >>And before we go down that route, let me point out that the 'amba bus'
> >>stuff in the kernel is there to support primecells, rather than all
> >>devices which the AMBA specification covers.
> >>
> >>The reason it's called 'amba' is because back in 2001 or so when the
> >>first primecell drivers were created, there was little information
> >>available as to what AMBA, AHB, or APB even covered. All I had to go
> >>on were the primecell documents themselves. The higher level documents
> >>were not available to me.
> >>
> >>So, despite it being called 'amba', it really is just for primecells
> >>and if we didn't have the exposure to userspace, I'd have renamed it to
> >>'apb' or similar instead.
> >
> >Okay, that clarifies things a lot, and lends weight to the arguement
> >that it is perfectly normal and acceptable to have both amba_devices
> >and platform_devices on the same bus segment. Are there any cases
> >where amba primecells are being driven by platform_drivers? If so,
> >should those drivers have an amba_driver registration added?
>
> I would be surprised if there are any implemented as
> platform_drivers that are not duplicates of an amba driver. The STMP
> uart is actually a pl011 and it's platform driver was recently

It (duart than auart) is a platform driver in Freesccale BSP, and was
turned into 'amba' one when being upstreamed.

> removed IIRC. So I think we can consider platform drivers something
> that should be fixed in this case.
>

--
Regards,
Shawn



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