[PATCH v2 6/6] common: Add an option to relocate on ram top

[Marek Vasut]

On 4/28/26 9:31 AM, Ilias Apalodimas wrote:
> On Tue, 28 Apr 2026 at 09:43, Marek Vasut <marek.vasut at mailbox.org> wrote:
>>
>> On 4/27/26 4:33 PM, Ilias Apalodimas wrote:
>>
>> [...]
>>
>>>>>>> +++ b/common/board_f.c
>>>>>>> @@ -339,7 +339,22 @@ static int setup_ram_base(void)
>>>>>>>      static int setup_ram_config(void)
>>>>>>>      {
>>>>>>>          debug("Monitor len: %08x\n", gd->mon_len);
>>>>>>> -#if CONFIG_VAL(SYS_MEM_TOP_HIDE)
>>>>>>> +
>>>>>>> +     if (CONFIG_IS_ENABLED(RELOC_ADDR_TOP)) {
>>>>>>> +             int bank;
>>>>>>> +             phys_size_t total_size = 0;
>>>>>>> +
>>>>>>> +             for (bank = 0; bank < CONFIG_NR_DRAM_BANKS; bank++) {
>>>>>>> +                     if (gd->ram_top <= gd->bi_dram[bank].start)
>>>>>>> +                             gd->ram_top = gd->bi_dram[bank].start +
>>>>>>> +                                             gd->bi_dram[bank].size;
>>>>>>> +                     total_size += gd->bi_dram[bank].size;
>>>>>>> +             }
>>>>>>> +             gd->ram_size = total_size;
>>>>>>
>>>>>> Shouldn't this also apply board_get_usable_ram_top() to be consistent ?
>>>>>
>>>>> Simon asked the same thing. I'd rather keep this option strict for now
>>>>> and always relocate to the upper memory boundary fnor now. Once I do
>>>>> further cleanups, I can either add it or remove the function entirely
>>>>> since dram_init_banksize() (which hs also board specific) runs really
>>>>> early now.
>>>>
>>>> Maybe the default board_get_usable_ram_top() can return the ram top if
>>>> CONFIG_IS_ENABLED(RELOC_ADDR_TOP) ? That would still allow users to use
>>>> board_get_usable_ram_top() consistently to reduce the ram top.
>>>
>>> dram_init_banksize() can be used instead now to reduce that and we can
>>> remove this option eventually. Is there anything that we can't achieve
>>> with only that ?
>> I think I might be confused, but it seems board_get_usable_ram_top() is
>> used to set gd->ram_top , which is U-Boot's top of RAM and may not be
>> the same as physical top of RAM . So no, dram_init_banksize() has to
>> configure the correct physical RAM topology, board_get_usable_ram_top()
>> can be used to make space at ram_top unavailable to U-Boot .
> 
> I don't think you are confused but what I am trying to do with this
> option here is make the process of relocating to the last bank
> standard. So people that want U-Boot to calculate the reloc address
> based on the information they initalized on dram_init_banksize() _ the
> reserved DT regions should enable this option. if they have their own
> per board calculation logic, they can leave it as is, in which case
> we'll still call board_get_usable_ram_top().
That I do understand, I think board_get_usable_ram_top(top) should by 
default return its input parameter "top" . If user does need to adjust 
their ram_top, they can override board_get_usable_ram_top() and possibly 
consume the "top" parameter too. That way, the user has the actual ram 
top at their disposal, and they can use it if they need it, instead of 
reimplementing the logic to get their ram top. Most users should ideally 
not override board_get_usable_ram_top() of course.