Re: [U-Boot] [PATCH v4 26/26] sunxi: A64: add 32-bit SPL support

[Maxime Ripard]

On Mon, Jan 16, 2017 at 09:47:06AM +, André Przywara wrote:
> On 16/01/17 08:55, Maxime Ripard wrote:
> > On Fri, Jan 13, 2017 at 09:42:28AM +, Andre Przywara wrote:
> >>> Re wanting to build SPL either as 32-bit or 64-bit, could this be a
> >>> Kconfig option perhaps?
> >>
> >> Sounds like a direction worth to investigate.
> >> In the moment we have two separate defconfig files, because CPU_V7 and
> >> ARM64 are actually mutually exclusive, which is really a pain and the
> >> main reason that part wasn't merged.
> > 
> > I really like that option.
> 
> So I gave this a try this weekend, I have something like:
> 
> +choice
> + prompt "32/64 bit build selection"
> + depends on MACH_SUN50I
> +
> +config SUNXI_64BIT_BUILD
> + bool "64-bit Aarch64 build"
> + select ARM64
> +
> +config SUNXI_32BIT_BUILD
> + bool "32-bit ARM build"
> + select CPU_V7
> + select PHYS_64BIT
> +
> +endchoice
> 
> I then set CONFIG_SUNXI_64BIT_BUILD=y in the defconfig.
> That seems to work, however switching to a 32-bit build requires either
> a) a separate defconfig - which is what we didn't want
> b) manually toggling this via menuconfig
> c) sed-ing these two lines in .config
> 
> I was hoping that there was some simple command line way of toggling a
> Kconfig option, à la:
> $ make pine64_plus_defconfig CONFIG_SUNXI_32BIT_BUILD=y
> 
> But that didn't work.
> mergeconfig.sh wasn't helpful as well.
> 
> Any ideas on how we could easily switch between the two options?

I know that Linux has a way to append defconfig fragments (originally
for android options iirc). That could be worth a look.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com


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Re: [U-Boot] [PATCH v4 26/26] sunxi: A64: add 32-bit SPL support

[André Przywara]

On 16/01/17 08:55, Maxime Ripard wrote:
> On Fri, Jan 13, 2017 at 09:42:28AM +, Andre Przywara wrote:
>>> Re wanting to build SPL either as 32-bit or 64-bit, could this be a
>>> Kconfig option perhaps?
>>
>> Sounds like a direction worth to investigate.
>> In the moment we have two separate defconfig files, because CPU_V7 and
>> ARM64 are actually mutually exclusive, which is really a pain and the
>> main reason that part wasn't merged.
> 
> I really like that option.

So I gave this a try this weekend, I have something like:

+choice
+   prompt "32/64 bit build selection"
+   depends on MACH_SUN50I
+
+config SUNXI_64BIT_BUILD
+   bool "64-bit Aarch64 build"
+   select ARM64
+
+config SUNXI_32BIT_BUILD
+   bool "32-bit ARM build"
+   select CPU_V7
+   select PHYS_64BIT
+
+endchoice

I then set CONFIG_SUNXI_64BIT_BUILD=y in the defconfig.
That seems to work, however switching to a 32-bit build requires either
a) a separate defconfig - which is what we didn't want
b) manually toggling this via menuconfig
c) sed-ing these two lines in .config

I was hoping that there was some simple command line way of toggling a
Kconfig option, à la:
$ make pine64_plus_defconfig CONFIG_SUNXI_32BIT_BUILD=y

But that didn't work.
mergeconfig.sh wasn't helpful as well.

Any ideas on how we could easily switch between the two options?

Cheers,
Andre.

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Re: [U-Boot] [PATCH v4 26/26] sunxi: A64: add 32-bit SPL support

[Maxime Ripard]

On Fri, Jan 13, 2017 at 09:42:28AM +, Andre Przywara wrote:
> > Re wanting to build SPL either as 32-bit or 64-bit, could this be a
> > Kconfig option perhaps?
> 
> Sounds like a direction worth to investigate.
> In the moment we have two separate defconfig files, because CPU_V7 and
> ARM64 are actually mutually exclusive, which is really a pain and the
> main reason that part wasn't merged.

I really like that option.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com


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Re: [U-Boot] [PATCH v4 26/26] sunxi: A64: add 32-bit SPL support

[Andre Przywara]

Hi,

On 13/01/17 02:19, Simon Glass wrote:
> Hi Andre,
> 
> On 2 January 2017 at 04:48, Andre Przywara  wrote:
>> When compiling the SPL for the Allwinner A64 in AArch64 mode, we can't
>> use the more compact Thumb2 encoding, which only exists for AArch32
>> code. This makes the SPL rather big, up to a point where any code
>> additions or even a different compiler may easily exceed the 32KB limit
>> that the Allwinner BROM imposes.
>> Introduce a separate, mostly generic sun50i-a64 configuration, which
>> defines the CPU_V7 symbol and thus will create a 32-bit binary using
>> the memory-saving Thumb2 encoding.
>> This should only be used for the SPL, the U-Boot proper should still be
>> using the existing 64-bit configuration. The SPL code can switch to
>> AArch64 if needed, so a 32-bit SPL can be combined with a 64-bit U-Boot
>> proper to eventually launch arm64 kernels.
>>
>> Signed-off-by: Andre Przywara 
>> ---
>>  board/sunxi/Kconfig| 14 --
>>  configs/pine64_plus_defconfig  |  2 +-
>>  configs/sun50i_spl32_defconfig | 10 ++
>>  3 files changed, 23 insertions(+), 3 deletions(-)
>>  create mode 100644 configs/sun50i_spl32_defconfig
> 
> Following up on the previous discussion, I take it that one on problem
> is that U-Boot does not support building SPL with one toolchain and
> U-Boot proper with another?

Yes. For the time being I have a script [1] that first configures and
compiles everything with an ARM cross compiler, then repeats this with
an aarch64 cross compiler. Then I combine the 32-bit SPL and the 64-bit
U-Boot proper.

While we are at it: I didn't find a Makefile target to just compile the
SPL (or just U-Boot proper), is that worth looking at? Or can we somehow
influence Kconfig options on the command line to achieve that on that level?

> Re wanting to build SPL either as 32-bit or 64-bit, could this be a
> Kconfig option perhaps?

Sounds like a direction worth to investigate.
In the moment we have two separate defconfig files, because CPU_V7 and
ARM64 are actually mutually exclusive, which is really a pain and the
main reason that part wasn't merged.

> Anyway, if this is what we have for now, fine. But I'd like to see at
> least a TODO suggesting a better solution.

So yes, the series was now merged omitting the 32-bit SPL part, which is
really optional. For the time being we seem to get away with only
64-bit, but I will definitely revisit this after having handled the
higher priority patches in my queue.

Cheers,
Andre.

[1] http://pastebin.com/kH7u2h7M
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Re: [U-Boot] [PATCH v4 26/26] sunxi: A64: add 32-bit SPL support

[Simon Glass]

Hi Andre,

On 2 January 2017 at 04:48, Andre Przywara  wrote:
> When compiling the SPL for the Allwinner A64 in AArch64 mode, we can't
> use the more compact Thumb2 encoding, which only exists for AArch32
> code. This makes the SPL rather big, up to a point where any code
> additions or even a different compiler may easily exceed the 32KB limit
> that the Allwinner BROM imposes.
> Introduce a separate, mostly generic sun50i-a64 configuration, which
> defines the CPU_V7 symbol and thus will create a 32-bit binary using
> the memory-saving Thumb2 encoding.
> This should only be used for the SPL, the U-Boot proper should still be
> using the existing 64-bit configuration. The SPL code can switch to
> AArch64 if needed, so a 32-bit SPL can be combined with a 64-bit U-Boot
> proper to eventually launch arm64 kernels.
>
> Signed-off-by: Andre Przywara 
> ---
>  board/sunxi/Kconfig| 14 --
>  configs/pine64_plus_defconfig  |  2 +-
>  configs/sun50i_spl32_defconfig | 10 ++
>  3 files changed, 23 insertions(+), 3 deletions(-)
>  create mode 100644 configs/sun50i_spl32_defconfig

Following up on the previous discussion, I take it that one on problem
is that U-Boot does not support building SPL with one toolchain and
U-Boot proper with another?

Re wanting to build SPL either as 32-bit or 64-bit, could this be a
Kconfig option perhaps?

Anyway, if this is what we have for now, fine. But I'd like to see at
least a TODO suggesting a better solution.

Regards,
Simon
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