[U-Boot] [PATCH] zynq: Use arch_cpu_init() instead of lowlevel_init()

Michal Simek
2013-10-03T06:58:38Z

On 10/02/2013 09:43 PM, Albert ARIBAUD wrote:
> Hi Michal,
>
> On Tue, 24 Sep 2013 12:38:38 +0200, Michal Simek <monstr@monstr.eu>
> wrote:
>
>> Hi Albert,
>>
>> On 09/23/2013 04:37 PM, Albert ARIBAUD wrote:
>>> Hi Michal,
>>>
>>> On Mon, 23 Sep 2013 16:19:52 +0200, Michal Simek <monstr@monstr.eu>
>>> wrote:
>>>
>>>> On 09/23/2013 02:31 PM, Albert ARIBAUD wrote:
>>>>> Hi Michal,
>>>>>
>>>>> On Thu, 22 Aug 2013 14:52:02 +0200, Michal Simek
>>>>> <michal.simek@xilinx.com> wrote:
>>>>>
>>>>>> Zynq lowlevel_init() was implemented in C but stack
>>>>>> pointer is setup after function call in _main().
>>>>>> Move architecture setup to arch_cpu_init() which is call
>>>>>> as the first function in board_init_f() which
>>>>>> already have correct stack pointer.
>>>>>>
>>>>>> Reported-by: Sven Schwermer <sven.schwermer@tuhh.de>
>>>>>> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
>>>>>> ---
>>>>>> I can't see any problem to call zynq setup a little
>>>>>> bit later. There is already expectation that u-boot
>>>>>> runs from DDR.
>>>>>> Moving lowlevel_init from C to ASM is possible but
>>>>>> I will have to introduce new macros with hardcoded
>>>>>> values. Using structures is much nicer.
>>>>>>
>>>>>> ---
>>>>>> arch/arm/cpu/armv7/zynq/cpu.c | 6 ++++++
>>>>>> 1 file changed, 6 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm/cpu/armv7/zynq/cpu.c b/arch/arm/cpu/armv7/zynq/cpu.c
>>>>>> index 4367d1a..8846f30 100644
>>>>>> --- a/arch/arm/cpu/armv7/zynq/cpu.c
>>>>>> +++ b/arch/arm/cpu/armv7/zynq/cpu.c
>>>>>> @@ -11,6 +11,10 @@
>>>>>>
>>>>>> void lowlevel_init(void)
>>>>>> {
>>>>>> +}
>>>>>
>>>>> I'd rather you deleted lowlevel_init() as a C function with this
>>>>> name should not exist.
>>>>
>>>> Ok. Do you want me to create almost empty low_level.S or just use
>>>> arch/arm/cpu/arvm7/lowlevel_init.S and define empty s_init()?
>>>
>>> Urgh. I realize removing the C function would give you more work than
>>> simply keeping it empty until the whole s_init() mess is cleaned up. :(
>>>
>>> I'll take your change as-is, sorry for the noise.
>>
>> In connection to this topic we have recently found one issue
>> regarding to neon instruction which u-boot uses.
>>
>> We have this code to enable them in asm and adding this to lowlevel_init.S
>> is straight way how to do so.
>> mov r0, r0
>> mrc p15, 0, r1, c1, c0, 2
>> orr r1, r1, #(0xf << 20)
>> mcr p15, 0, r1, c1, c0, 2
>>
>> fmrx r1, FPEXC
>> orr r1,r1, #(1<<30)
>> fmxr FPEXC, r1
>>
>> Is it ok to create zynq asm specific lowlevel function
>> or doing this through s_init() or you have nice a clean way how
>> this should be solved when you are saying that s_init() is mess.
>
> Sorry for responding slowly.
>
> I suspect when you say neon instruction that U-Boot uses, you mean neon
> instructions that GCC is allowed to emit while building U-Boot, right?

yes.

> So we're talking about neon insns in C code only, not asm, correct?

yes. gcc emits neon instruction in timer code. Not in asm.

> If this is correct, then does something prevent you from enabling
> neon instructions as early as possible, in e.g. the lowlevel_init
> routine?

ok let me clear this. I think location of this code is clear.
It is asm code and it will be called ASAP even
we know exactly which code emits neon instructions.
My point was if we should create specific lowlevel_init asm function
and add this code there.
Or use arch/arm/cpu/armv7/lowlevel_init.S and create just s_init function.

You mentioned above that s_init() is a mess and needs to be clean up
but you didn't mentioned how.

It means my point is if you tell us how should be clean up we can
just submit code which is compatible with this cleanup activity.

Thanks,
Michal

--
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform

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