Information regarding iMX6 QuadPlus and iMX6 DualLite

[gianluca]

On 03/23/2017 04:15 PM, Lucas Stach wrote:
> Hi,
>
> Am Donnerstag, den 23.03.2017, 16:04 +0100 schrieb gianluca:
>> Hello,
>> I was looking around to have a common Barebox binary to bootup two
>> boards based on iMX6 SoC.
>>
>> The PCB are at 99.8% the same.
>> PCB#0 has iMX6QP and a VDDCore of 1.38V (LDO enabled)
>> PCB#1 has iMX6DL and a VDDCore of 1.32V (LDO enabled)
>>
>> I was wondering how other boards (like Nitrogen6x) does for booting.
>>
>> As soon as my boards have the same DDR Memory routing and types, the oly
>> thing I can think is the different memory address space for DDR controller.
>
> Even if the external memory is the same, you need 2 different DRAM
> setups. Quad and DualLite differ in IOMUX setup and maximum DRAM
> frequency, the QuadPlus needs additional setup for the NoC.
>

So you need two DRAM setup only? And no problem for NoC. Our boards will 
have only QuadPlus and DualLite.

>> In fact, the Nitrogen6x boards, differs from the #include of the ddr
>> controller (one is for dual-lite, the other for quad).
>
> For the Nitrogen boards we just build multiple images for different
> SoC/DRAM configurations. This is the easiest and most reliable way of
> dealing with this issue.
>

So you will have different device-tree .dts file? One for each SoC even 
if the pinout are the same?

In this way, having two DRAM Setups, two IOMUX setup, different DRAM 
Frequencies and two device-tree blobs, this leads me to a conclusion:

-- They are TWO DIFFERENT BOARDS (even the PCB and the pinouts are the same)

Luckly the Linux kernel is the same, and even the rootfilesystem too.


>>
>> But I do not found any switch between choosing one Soc or another.
>> Where is done the startup entry?
>
> If you want a single binary, you need build a 2 stage barebox. First
> stage needs to be loaded into SRAM, then you can look at which board you
> are running and do the specific DRAM setup. Then you can load the bigger
> 2nd stage into DRAM, where you again need to look at the board you are
> running at and select the correct devicetree for barebox to use.
>
>> And the maximum clock speed??? Those SoC has different clock maximum
>> speed, so I think someone has to tell it to run @800 Mhz or @1Ghz. Is
>> this true?
>
> Clock speeds are defined by the CPU OPPs in the devicetree and the fuse
> settings of the SoC.
>

Ok, I will check that.

Thank you for now,

-- 
Eurek s.r.l.                          |
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