[U-Boot] [PATCH 1/3] ARmv7: Add a soc_init hook to start.S

[Hans de Goede]

Hi,

On 26-01-15 09:09, Albert ARIBAUD wrote:
> Hello Tom,
>
> On Thu, 22 Jan 2015 11:20:58 -0500, Tom Rini <trini at ti.com> wrote:
>> On Wed, Jan 21, 2015 at 09:03:25PM +0100, Hans de Goede wrote:
>>
>>> On some SoCs / ARMv7 CPU cores we need to do some setup before enabling the
>>> icache, etc. Add a soc_init hook with a weak default which just calls
>>> cpu_init_cp15.
>>>
>>> This way different implementations can be provided to do some extra work
>>> before or after cpu_init_cp15, or completely replacing cpu_init_cp15.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>> ---
>>>   arch/arm/cpu/armv7/start.S | 18 +++++++++++++++++-
>>>   1 file changed, 17 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
>>> index fdc05b9..9882b20 100644
>>> --- a/arch/arm/cpu/armv7/start.S
>>> +++ b/arch/arm/cpu/armv7/start.S
>>> @@ -64,7 +64,7 @@ reset:
>>>
>>>   	/* the mask ROM code should have PLL and others stable */
>>>   #ifndef CONFIG_SKIP_LOWLEVEL_INIT
>>> -	bl	cpu_init_cp15
>>> +	bl	soc_init
>>>   	bl	cpu_init_crit
>>>   #endif
>>
>> I like the direction here.
>
> I don't like all of it, specifically the double call, to cpu_init_cp15
> then soc_init, for two reasons:
>
> 0) soc_init might touch cp15, but it's hidden in the name whereas it is
>     shown in cpu_init_cp15. Either both names should explicitly say they
>     are touching cp15, or both should not.
>
> 1) we cannot tell if cpu_init_cp15 should always happen before
>     soc_init. Having a single call to soc_init, with the understanding
>     that it will handle the cpu_init_cp15 call itself, makes it
>     possible for soc_init yo decide whether it wants to call
>     cpu_init_cp15 first, last or at all.

There is no double call, the call to cpu_init_cp15 is being replaced with
a call to soc_init, which then can call cpu_init_cp15 at any time it likes.

Also see the discussion further in the thread about replacing soc_init
with a call to lowlevel_init which then call s_init which may then call
cpu_init_cp15 at a convenient time, the advantage of this approach is that
the soc / board specific code can be written in C rather then in asm.

Regards,

Hans