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

[Chris Packham]

On 12/15/2014 11:37 PM, Arnd Bergmann wrote:
> On Monday 15 December 2014 00:57:49 Chris Packham wrote:
>> On 12/15/2014 10:11 AM, Chris Packham wrote:
>>>>> +
>>>>> +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
>>>
>
> I still think we should not duplicate this but instead change the
> header files to make the include hack unnecessary in all those places.
>
> Looking at the header file, it only contains
>
> #include <linux/libfdt_env.h>
> #include "../../scripts/dtc/libfdt/fdt.h"
> #include "../../scripts/dtc/libfdt/libfdt.h"
>
> so two of them get the headers from exactly that place, while the
> libfdt_env.h file contains the linux-specific implementation of
> a couple of functions instead of the baremetal implementation.
>
> It looks like the intention was that when you already include the
> linux version of the header, you no longer need the other one, but
> that assumption is broken by current implementation.
>
> One way to solve this would be
>
> diff --git a/scripts/dtc/libfdt/libfdt.h b/scripts/dtc/libfdt/libfdt.h
> index 73f49759a5e7..23c55baa8e18 100644
> --- a/scripts/dtc/libfdt/libfdt.h
> +++ b/scripts/dtc/libfdt/libfdt.h
> @@ -51,7 +51,7 @@
>    *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>    */
>
> -#include <libfdt_env.h>
> +#include "libfdt_env.h"
>   #include <fdt.h>
>
>   #define FDT_FIRST_SUPPORTED_VERSION	0x10
>
>
> but I'm not sure if that is the best way.
>

I was hoping to limit the scope of my changes to mvebu code. But I can 
give it a whirl. I agree that propagating the hack isn't ideal.

>>>> 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.
>>
>> Adding the following at the top will do the trick (assuming
>> "marvell,armada370" is the right compatible string to use).
>>
>>          unsigned long root = of_get_flat_dt_root();
>>
>>          if (of_flat_dt_is_compatible(root, "marvell,armada370"))
>>                  return;
>
> Right. You could also add
>
> 	if (!IS_ENABLED(CONFIG_SMP) || !of_flat_dt_is_compatible(root, "marvell,armadaxp")))
>
> to again eliminate that check for uniprocessor kernels, and to not
> propagate the fixup to future machines but make it clear that
> it is only needed for armadaxp.

OK makes sense.

>
> 	Arnd
>