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

[Chris Packham]

Hi Arnd,

On 12/13/2014 12:35 AM, Arnd Bergmann wrote:
> 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> ?
>

I am already including linux/libfdt.h. Without the CFLAGS change I get
the following compile error.

   In file included from include/linux/libfdt.h:6:0,
                    from arch/arm/mach-mvebu/board-v7.c:21:
   include/linux/../../scripts/dtc/libfdt/libfdt.h:54:24: fatal error: 
libfdt_env.h: No such file or directory

There seems to be precedence in other architectures/drivers

   $ git grep -e '-I.*libfdt'
   arch/mips/cavium-octeon/Makefile:CFLAGS_octeon-platform.o = 
-I$(src)/../../../scripts/dtc/libfdt
   arch/mips/cavium-octeon/Makefile:CFLAGS_setup.o = 
-I$(src)/../../../scripts/dtc/libfdt
   arch/mips/mti-sead3/Makefile:CFLAGS_sead3-setup.o = 
-I$(src)/../../../scripts/dtc/libfdt
   arch/powerpc/kernel/Makefile:CFLAGS_prom.o              = 
-I$(src)/../../../scripts/dtc/libfdt
   drivers/firmware/efi/libstub/Makefile:CFLAGS_fdt.o 
    += -I$(srctree)/scripts/dtc/libfdt/
   drivers/of/Makefile:CFLAGS_fdt.o = -I$(src)/../../scripts/dtc/libfdt
   drivers/of/Makefile:CFLAGS_fdt_address.o = 
-I$(src)/../../scripts/dtc/libfdt

>> +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
>

Any suggestion as to what to check for. Based on the dts files in the
current source seem compatible == "marvell,armada370" seems like a good
choice. But I don't know for sure that there isn't a armada-xp variant
out using a .dts with this set.

Another option might be just to count the /cpu at n nodes.