Re: [RFC PATCH 2/2] ARM: DT: kernel: DT cpu node bindings update

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Wed, Apr 17, 2013 at 10:35:24AM +0100, Nicolas Ferre wrote:
> On 04/15/2013 06:13 PM, Lorenzo Pieralisi :
> > In order to extend the current cpu nodes bindings to newer CPUs
> > inclusive of AArch64 and to update support for older ARM CPUs this
> > patch updates device tree documentation for the cpu nodes bindings.
> > 
> > Main changes:
> > 
> > - adds 64-bit bindings (inclusive of cpus node #address-cells updates)
> > - defines behaviour on pre and post v7 uniprocessor systems
> > - adds ARM 11MPcore specific reg property definition
> > 
> > DT cpu map parsing code must be made compliant with the latest bindings
> > updates, hence this patch also updates the arm_dt_init_cpu_maps() function
> > with checks and additional parsing rules.
> > 
> > Uniprocessor systems predating v7 do not parse the cpus node at all
> > since the reg property is meaningless on those systems.
> > 
> > Device trees for 64-bit systems can be taken as device tree input also
> > for 64-bit CPUs running in 32-bit mode. The code checks that the reg entries
> > are zeroed as required in the respective fields and detects automatically
> > the cpus node #address-cells value so that device tree written for
> > 64-bit ARM platforms (cpus #address-cells == 2) can still be taken as
> > input. The correct device tree entries are to be set up by the boot
> > loader, kernel code just checks that device tree entries in the cpus
> > node are as expected for a 32-bit CPU (reg[63:24] == 0).
> > 
> > cpu node entries with invalid reg property or containing duplicates are
> > ignored and the device tree parsing is not stopped anymore when such
> > entries are encountered, the device tree cpu entry is just skipped.
> > 
> > A device tree with cpu nodes missing the boot CPU MPIDR is considered a
> > hard error and the kernel flags this up as a bug to force firmware updates.
> > 
> > The updates to cpus/cpu node bindings for ARM require all in-kernel dts files
> > present in the mainline to be made compliant to the latest specification.
> > 
> > This patch also updates ARM in-kernel non-compliant dts files to the latest
> > cpus/cpu nodes bindings specification.
> > 
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > ---
> >  Documentation/devicetree/bindings/arm/cpus.txt | 335 +++++++++++++++++++++----
> >  arch/arm/boot/dts/exynos5440.dtsi              |   7 +
> >  arch/arm/boot/dts/omap3.dtsi                   |   4 +
> >  arch/arm/boot/dts/omap4.dtsi                   |   5 +
> >  arch/arm/boot/dts/omap5.dtsi                   |   5 +
> >  arch/arm/boot/dts/r8a7740.dtsi                 |   3 +
> >  arch/arm/boot/dts/sh7372.dtsi                  |   4 +
> >  arch/arm/boot/dts/sunxi.dtsi                   |   4 +
> 
> Hi,
> 
> If it can be done easily, can you please consider the upcoming (3.10)
> cortex-a5 SoC:
> 
> arch/arm/boot/dts/sama5d3.dtsi
> 
> It is in linux-next through arm-soc/at91/at91/soc

I will do that at the same time this set gets merged.

> >  arch/arm/kernel/devtree.c                      |  82 +++---
> >  9 files changed, 377 insertions(+), 72 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
> > index f32494d..b1ef3d8 100644
> > --- a/Documentation/devicetree/bindings/arm/cpus.txt
> > +++ b/Documentation/devicetree/bindings/arm/cpus.txt
> > @@ -1,4 +1,6 @@
> > -* ARM CPUs binding description
> > +=============================
> > +ARM CPUs bindings description
> > +=============================
> >  
> >  The device tree allows to describe the layout of CPUs in a system through
> >  the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
> > @@ -8,70 +10,317 @@ Bindings for CPU nodes follow the ePAPR standard, available from:
> >  
> >  http://devicetree.org
> >  
> > -For the ARM architecture every CPU node must contain the following properties:
> > -
> > -- device_type:	must be "cpu"
> > -- reg:		property matching the CPU MPIDR[23:0] register bits
> > -		reg[31:24] bits must be set to 0
> > -- compatible:	should be one of:
> > -		"arm,arm1020"
> > -		"arm,arm1020e"
> > -		"arm,arm1022"
> > -		"arm,arm1026"
> > -		"arm,arm720"
> > -		"arm,arm740"
> > -		"arm,arm7tdmi"
> > -		"arm,arm920"
> 
> Here we have: "arm,arm920t" for at91rm9200.dtsi

I will update it.

> > -		"arm,arm922"
> > -		"arm,arm925"
> > -		"arm,arm926"
> 
> Oh, I missed this one: the strange thing is that *all* arm926 variants
> have a compatible string of this form: "arm,arm926ejs"
> 
> (using: git grep "arm,arm9" next/master)
> 
> Should we change? Is there a rule for this naming?

We decided to keep the compatible property as the base processor
names, leaving out variants, so I think answer is: the rule for the
naming is this document, and yes we should change it, if we all agree
on the approach.

Lorenzo