Re: [PATCH] arm/dt: Add SoC detection macros

Jean-Christophe PLAGNIOL-VILLARD
2011-09-17T18:19:07Z

On 12:23 Sat 17 Sep , Russell King - ARM Linux wrote:
> On Sat, Sep 17, 2011 at 12:34:57PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > On 11:28 Sat 17 Sep , Russell King - ARM Linux wrote:
> > > One last point to raise here is - and it's quite a fundamental one - do we
> > > really want this? If we're making decisions based on the SoC type, that
> > > suggests to me that the hardware description in DT is incomplete, and
> > > we're hiding stuff in the kernel behind the SoC type. That doesn't sound
> > > particularly appealing given the point of DT is to encode the hardware
> > > specific information outside the kernel code.
> >
> > except if a machine can run on 2 soc so detect it will avoid to have 2 Device
> > Tree
>
> This code is structured to match the SoC based upon an entry in the DT,
> so for tegra2 vs tegra3 it's already having to have two different DTs
> to distinguish between them.
>
> However, I still go back to my original point: the point of DT is to
> provide a description of the hardware which the kernel is running on -
> not only for current hardware but possibly future hardware as well. Eg,
> if Tegra4 comes along with more peripherals than Tegra3 but has basic
> hardware which the kernel already supports, just wired up differently,
> then Tegra4 should just work with a new DT file and no code changes.
>
> What I'm saying is that in that scenario it should not be necessary to
> edit the kernel to invent new SoC types, and then teach it that Tegra4
> is mostly the same as Tegra3. That information should all be encoded
> into the DT rather than the C code in the kernel.
>
> So, I think adding this SoC type stuff is the wrong approach to the
> problem.

I agree about it I just mean that if you have the same board with 2 SoC which
are pin to pin compatible detect the soc type will be usefull as the soc
resource may not be the same

Best Regards,
J.