[PATCH] arm64: dts: add device tree for ARM SMM-A53x2 on LogicTile Express 20MG

[mark.rutland@arm.com (Mark Rutland)]

On Wed, Jun 10, 2015 at 09:58:25AM +0100, Liviu Dudau wrote:
> Hi Kristina,
> 
> On Tue, Jun 09, 2015 at 04:38:31PM +0100, Kristina Martsenko wrote:
> > Add a DTS file for the MP2 Cortex-A53 Soft Macrocell Model implemented
> > on a LogicTile Express 20MG (V2F-1XV7) daughterboard. This is based on
> > the version that's currently available from the ARM DTS repository [1].
> > 
> > [1] git://linux-arm.org/arm-dts.git
> 
> I thought the plan was to keep new DTs in this repository, not to add
> them into the kernel. Has this changed?
> 
> > 
> > Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
> > ---
> >  MAINTAINERS                                        |   1 +
> >  arch/arm64/boot/dts/arm/Makefile                   |   1 +
> >  .../boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts      | 196 +++++++++++++++++++++
> >  3 files changed, 198 insertions(+)
> >  create mode 100644 arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 9180f46..1fb07e0 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -1613,6 +1613,7 @@ M:	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> >  L:	linux-arm-kernel at lists.infradead.org (moderated for non-subscribers)
> >  S:	Maintained
> >  F:	arch/arm/boot/dts/vexpress*
> > +F:	arch/arm64/boot/dts/arm/vexpress*
> >  F:	arch/arm/mach-vexpress/
> >  F:	*/*/vexpress*
> >  F:	*/*/*/vexpress*
> 
> You might want to Cc Lorenzo on this patch if you add him as maintainer :)
> 
> > diff --git a/arch/arm64/boot/dts/arm/Makefile b/arch/arm64/boot/dts/arm/Makefile
> > index c5c98b9..bb3c072 100644
> > --- a/arch/arm64/boot/dts/arm/Makefile
> > +++ b/arch/arm64/boot/dts/arm/Makefile
> > @@ -1,6 +1,7 @@
> >  dtb-$(CONFIG_ARCH_VEXPRESS) += foundation-v8.dtb
> >  dtb-$(CONFIG_ARCH_VEXPRESS) += juno.dtb juno-r1.dtb
> >  dtb-$(CONFIG_ARCH_VEXPRESS) += rtsm_ve-aemv8a.dtb
> > +dtb-$(CONFIG_ARCH_VEXPRESS) += vexpress-v2f-1xv7-ca53x2.dtb
> >  
> >  always		:= $(dtb-y)
> >  subdir-y	:= $(dts-dirs)
> > diff --git a/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts b/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> > new file mode 100644
> > index 0000000..bbe28aa
> > --- /dev/null
> > +++ b/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> > @@ -0,0 +1,196 @@
> > +/*
> > + * ARM Ltd. Versatile Express
> > + *
> > + * LogicTile Express 20MG
> > + * V2F-1XV7
> > + *
> > + * Cortex-A53 (2 cores) Soft Macrocell Model
> > + *
> > + * HBI-0247C
> > + */
> > +
> > +/dts-v1/;
> > +
> > +/* In use by spinning secondaries */
> > +/memreserve/ 0x80000000 0x00010000;
> 
> Where does the kernel get loaded to? If 0x80000000 is the start of memory and the kernel is
> loaded at 0x80000 offset as usual, then that memory is protected anyway.

That's simply not true. The kernel may use _any_ memory which is
described to it and not explicitly reserved.

We only reserve the kernel's static image (see arm64_memblock_init),
which does not cover that region. We can easily map that memory and
allocate it to something.

While we used to place page tables in the end of that region, we only
reserved the page tables, and it was problematic because you had no idea
how much of that memory the kernel might use.

Regardless, DTs should not rely on Linux implementation details like
magic implicit reservations.

Mark.