[U-Boot] [PATCH v1] armv8: fsl-layerscale: Rewrite reserving memory for MC and debug server

[York Sun <yorksun@freescale.com>]

On 11/16/2015 09:21 AM, Joakim Tjernlund wrote:
> On Mon, 2015-11-16 at 09:03 -0800, York Sun wrote:
>>
>> On 11/12/2015 02:54 PM, Joakim Tjernlund wrote:
>>> On Thu, 2015-11-12 at 14:20 -0800, York Sun wrote:
>>>> Introduce a new function to calculate reserved memory to replace macro
>>>> CONFIG_SYS_MEM_TOP_HIDE for more flexibility. Legacy use of this macro is
>>>> still supported. MC and debug server are not board-specific. Move the
>>>> reservation function to SoC file. Reduce debug server memory by 2MB to
>>>> make room for secure memory.
>>>
>>> I would make sure "pram" is first to reserve memory, is it?
>>>
>>
>> (previous reply wasn't caught by patchwork, adding more info)
>>
>> Yes, pram is used to reserve small memory from the top of u-boot memory, not
>> necessarily the top of total memory. For example, a 32-bit u-boot with large
>> memory. This patch deals with carving memory from the end of memory, which could
>> be far away from u-boot top. Even in system with small memory, it is still
>> correct, because pram reserves memory from the _top_ of u-boot and this
>> mechanism reserved memory is hidden from u-boot.
> 
> And I realize I am mixing pram and CONFIG_SYS_MEM_TOP_HIDE. Your patch
> reserves memory before CONFIG_SYS_MEM_TOP_HIDE which might be confusing
> for some. Why do you need another( then CONFIG_SYS_MEM_TOP_HIDE) method to reserve memory?
> 

I am not going to discover the legacy reason to have CONFIG_SYS_MEM_TOP_HIDE.
For my current use on ARMv8, we have management complex (aks MC) and debug
server. They both require a big chunk of private memory (even after OS boots
up). I am taking advantage of existing CONFIG_SYS_MEM_TOP_HIDE to reserve this
memory without fragment memory and without the need to create reserved memory
node in device tree.

With that in place, I think it makes sense to do the same way for reserving
secure memory.

York