[U-Boot] [RFC PATCH] common: board_f: Make reserve_mmu a weak function

[Simon Glass]

Hi Michal,

On 18 July 2017 at 07:23, Michal Simek <michal.simek at xilinx.com> wrote:
> Hi Simon,
>
> On 18.7.2017 16:01, Simon Glass wrote:
>> Hi Michal,
>>
>> On 13 July 2017 at 06:50, Michal Simek <michal.simek at xilinx.com> wrote:
>>> From: Siva Durga Prasad Paladugu <siva.durga.paladugu at xilinx.com>
>>>
>>> Make reserve_mmu a weak so that it provides an option
>>> to customize this routine as per platform need
>>
>> Why do you need this? Can we instead have the generic code do the
>> right thing? Or can we use reserve_arch() to handle this?
>
> reserve_mmu is called just for ARM.

What arch are you using?

> What we need to do is support configuration where we have small memory
> OCM and we need to put mmu table to different location (TCM) because it
> is simply big and it can't be placed where it is placed now.

What is TCM? Is this the internal SRAM?

I don't understand 'simply big'. Are you saying it is too big to go
into main memory?

>
> Based on looking at code the key question is if we can call reserve_mmu
> at that time when reserve_arch is called now.
> On zynqmp I can't see any issue to allocate tlb on the stack and call it
> from it. The question is if this is valid for all arms.
>
> This is just a small hack I have created to move it to stack.
>
>  diff --git a/common/board_f.c b/common/board_f.c
>  index 88e20e0168b2..32386c957962 100644
>  --- a/common/board_f.c
>  +++ b/common/board_f.c
>  @@ -433,13 +433,13 @@ __weak int reserve_mmu(void)
>   {
>          /* reserve TLB table */
>          gd->arch.tlb_size = PGTABLE_SIZE;
>  -       gd->relocaddr -= gd->arch.tlb_size;
>  +       gd->start_addr_sp -= gd->arch.tlb_size;
>
>          /* round down to next 64 kB limit */
>  -       gd->relocaddr &= ~(0x10000 - 1);
>  +       gd->start_addr_sp &= ~(0x10000 - 1);
>
>  -       gd->arch.tlb_addr = gd->relocaddr;
>  -       debug("TLB table from %08lx to %08lx\n", gd->arch.tlb_addr,
>  +       gd->arch.tlb_addr = gd->start_addr_sp;
>  +       printf("TLB table from %08lx to %08lx\n", gd->arch.tlb_addr,
>                gd->arch.tlb_addr + gd->arch.tlb_size);
>
>   #ifdef CONFIG_SYS_MEM_RESERVE_SECURE
>  @@ -837,7 +837,7 @@ static int initf_dm(void)
>   /* Architecture-specific memory reservation */
>   __weak int reserve_arch(void)
>   {
>  -       return 0;
>  +       return reserve_mmu();
>   }
>
>   __weak int arch_cpu_init_dm(void)
>  @@ -998,10 +998,6 @@ static init_fnc_t init_sequence_f[] = {
>          reserve_pram,
>   #endif
>          reserve_round_4k,
>  -#if !(defined(CONFIG_SYS_ICACHE_OFF) &&
> defined(CONFIG_SYS_DCACHE_OFF)) && \
>  -               defined(CONFIG_ARM)
>  -       reserve_mmu,
>  -#endif
>   #ifdef CONFIG_DM_VIDEO
>          reserve_video,
>   #else
>
> For us we can't just rewrite tlb addresses as we want to do because we
> can't allow reserve_mmu to allocate 64kB alied PGTABLE_SIZE in
> relocation structure.

Why not?

> What do you think?
>
> Thanks,
> Michal
>

Regards,
Simon