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

[Michal Simek]

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 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.

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.
What do you think?

Thanks,
Michal