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

[Marek Vasut]

On 06/16/2018 01:21 AM, Laurent Pinchart wrote:
> Hi Marek,
> 
> On Friday, 15 June 2018 15:00:31 EEST Marek Vasut wrote:
>> 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 ?
> 
> That's correct, ATF stores information about the memory layout at a fixed 
> address in system memory, and U-Boot can read it.

Well, that sounds good ! Maybe we can avoid adding SMC call altogether
then? :)

-- 
Best regards,
Marek Vasut