[RFC/PATCH 1/4 PATCH] ARM: mvebu: use dt_fixup to provide fallback for enable-method

[Arnd Bergmann]

On Friday 12 December 2014 17:53:55 Chris Packham wrote:
> > I briefly explored that approach here[1]. The tricky part would be 
> > handling the fact that the enable method can be attached to either the 
> > /cpus node or and individual /cpu entry (or is that something I can 
> > ignore?).
> > 
> > In the end I thought that the unconditional setting of smp_ops was 
> > easier to implement and would achieve the same result.
> 
> Actually as it turns out it's not that hard to implement something that
> checks both /cpus and /cpus/cpu at n. I'll include this with the next round
> after I've waited for anymore feedback.

Ah, very nice!

> ---8<---
> Subject: [PATCH] ARM: mvebu: use dt_fixup to provide fallback for enable-method
> 
> When the device tree doesn't define an enable-method insert a property
> into the flattened device tree. arm_dt_init_cpu_maps() will then parse
> this an set smp_ops appropriately. Now that we have this fallback it is
> no longer necessary to set .smp in the DT_MACHINE definition.
> 
> Signed-off-by: Chris Packham <chris.packham at alliedtelesis.co.nz>
> ---
>  arch/arm/mach-mvebu/Makefile   |  2 ++
>  arch/arm/mach-mvebu/board-v7.c | 37 ++++++++++++++++++++++++++++++++++++-
>  2 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-mvebu/Makefile b/arch/arm/mach-mvebu/Makefile
> index e24136b..68310f8 100644
> --- a/arch/arm/mach-mvebu/Makefile
> +++ b/arch/arm/mach-mvebu/Makefile
> @@ -14,3 +14,5 @@ endif
>  obj-$(CONFIG_MACH_DOVE)		 += dove.o
>  obj-$(CONFIG_MACH_KIRKWOOD)	 += kirkwood.o kirkwood-pm.o
>  obj-$(CONFIG_MACH_NETXBIG)	 += netxbig.o
> +
> +CFLAGS_board-v7.o = -I$(src)/../../../scripts/dtc/libfdt
> \ No newline at end of file

Why is this needed? Can't you just include <linux/libfdt.h> ?

> +static void __init armada_370_xp_dt_fixup(void)
> +{
> +	int offset, node;
> +	int i, len;
> +	void *prop;
> +	char buffer[20];
> +
> +	offset = fdt_path_offset(initial_boot_params, "/cpus");
> +	if (offset < 0)
> +		return;
> +
> +	prop = fdt_getprop(initial_boot_params, offset, "enable-method", &len);
> +	if (prop)
> +		return;
> +
> +	for (i = 0; i < NR_CPUS; i++) {
> +		snprintf(buffer, sizeof(buffer), "cpu@%d", i);
> +		node = fdt_subnode_offset(initial_boot_params, offset, buffer);
> +		if (node < 0)
> +			break;
> +		prop = fdt_getprop(initial_boot_params, node,
> +				   "enable-method", &len);
> +		if (prop)
> +			return;
> +	}
> +
> +	pr_info("No enable-method defined. "
> +		"Falling back to \"marvell,armada-xp-smp\"\n");
> +
> +	fdt_setprop(initial_boot_params, offset, "enable-method",
> +		    "marvell,armada-xp-smp", sizeof("marvell,armada-xp-smp"));
> +}

I think it would be good to first check whether you are running on Armada XP
or Armada 370, because the latter does not require this.

	Arnd