Re: [PATCH v4 02/10] memblock: Add variables for usable memory limitation

[Geert Uytterhoeven]

On Wed, Jul 14, 2021 at 3:51 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:
> > Add two global variables (cap_mem_addr and cap_mem_size) for storing a
> > base address and size, describing a limited region in which memory may
> > be considered available for use by the kernel.  If enabled, memory
> > outside of this range is not available for use.
> >
> > These variables can by filled by firmware-specific code, and used in
> > calls to memblock_cap_memory_range() by architecture-specific code.
> > An example user is the parser of the "linux,usable-memory-range"
> > property in the DT "/chosen" node.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > ---
> > This is similar to how the initial ramdisk (phys_initrd_{start,size})
> > and ELF core headers (elfcorehdr_{addr,size})) are handled.
> >
> > Does there exist a suitable place in the common memblock code to call
> > "memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
> > have to be done in architecture-specific code?
>
> Can't you just call it from early_init_dt_scan_usablemem? If the
> property is present, you want to call it. If the property is not
> present, nothing happens.

Seems to work fine when called from early_init_dt_scan_nodes().
Hence v5 will no longer need to touch memblock.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds