[U-Boot] [RFC] ARM: rmobile: create DT memory nodes for R8A7795 3.0 and newer

[Marek Vasut]

On 06/15/2018 01:43 PM, Marek Vasut wrote:
> On 06/15/2018 12:37 PM, Ulrich Hecht wrote:
>> On Fri, Jun 15, 2018 at 12:09 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
>>>> +             arm_smccc_smc(ARM_SMCCC_RENESAS_MEMCONF,
>>>> +                           0, 0, 0, 0, 0, 0, 0, &res);
>>>
>>> Will this call work on platforms without patched ATF ?
>>> (I think not, don't you need to handle return value?)
>>
>> I have not actually tested that, but if I understand the ATF code
>> correctly, unimplemented calls return
>> SMC_UNK (0xffffffff), which should be handled by the default case (NOP) below.
> 
> Which means the board has a memory size of 0 and fails to boot ?
> 
>>>> +             switch (res.a0) {
>>>> +             case 1:
>>>> +                     base[0] = 0x048000000ULL;
>>>> +                     size[0] = 0x038000000ULL;
>>>> +                     base[1] = 0x500000000ULL;
>>>> +                     size[1] = 0x040000000ULL;
>>>> +                     base[2] = 0x600000000ULL;
>>>> +                     size[2] = 0x040000000ULL;
>>>> +                     base[3] = 0x700000000ULL;
>>>> +                     size[3] = 0x040000000ULL;
>>>> +                     fdt_fixup_memory_banks(blob, base, size, 4);
>>>> +                     break;
>>>> +             case 2:
>>>> +                     base[0] = 0x048000000ULL;
>>>> +                     size[0] = 0x078000000ULL;
>>>> +                     base[1] = 0x500000000ULL;
>>>> +                     size[1] = 0x080000000ULL;
>>>> +                     fdt_fixup_memory_banks(blob, base, size, 2);
>>>> +                     break;
>>>> +             case 3:
>>>> +                     base[0] = 0x048000000ULL;
>>>> +                     size[0] = 0x078000000ULL;
>>>> +                     base[1] = 0x500000000ULL;
>>>> +                     size[1] = 0x080000000ULL;
>>>> +                     base[2] = 0x600000000ULL;
>>>> +                     size[2] = 0x080000000ULL;
>>>> +                     base[3] = 0x700000000ULL;
>>>> +                     size[3] = 0x080000000ULL;
>>>> +                     fdt_fixup_memory_banks(blob, base, size, 4);
>>>> +                     break;
>>>
>>> Obvious design question is -- since you're adding new SMC call anyway,
>>> can't the call just return the memory layout table itself, so that it
>>> won't be duplicated both in U-Boot and ATF ?
>>
>> My gut feeling was to go with the smallest interface possible.
> 
> But this doesn't scale. The API here uses some ad-hoc constants to
> identify memory layout tables which have to be encoded both in ATF and
> U-Boot, both of which must be kept in sync.
> 
> The ATF already has those memory layout tables, it's only a matter of
> passing them to U-Boot. If you do just that, the ad-hoc constants and
> encoding of tables into U-Boot goes away and in fact simplifies the design.
> 
> Yet, I have to wonder if ATF doesn't already contain some sort of
> standard SMC call to get memory topology. It surprises me that it wouldn't.

In fact, Laurent (CCed) was solving some similar issue with lossy decomp
and I think this involved some passing of memory layout information from
ATF to U-Boot too, or am I mistaken ?

-- 
Best regards,
Marek Vasut