Re: [PATCH v5 1/2] dt-bindings: mtd: amlogic,meson-nand: support fields for boot ROM code

[Arseniy Krasnov]

On 07.05.2024 10:27, Miquel Raynal wrote:
> Hi Arseniy,
> 
> avkrasnov@xxxxxxxxxxxxxxxxx wrote on Tue, 7 May 2024 09:53:06 +0300:
> 
>> On 06.05.2024 16:48, Miquel Raynal wrote:
>>> Hi Arseniy,
>>>
>>> avkrasnov@xxxxxxxxxxxxxxxxx wrote on Tue, 16 Apr 2024 11:51:00 +0300:
>>>   
>>>> Boot ROM code on Meson requires that some pages on NAND must be written
>>>> in special mode: "short" ECC mode where each block is 384 bytes and
>>>> scrambling mode is on.  
>>>
>>> Ok
>>>   
>>>> Such pages located with the specified interval within specified offset.  
>>>
>>> I'm sorry I don't get that sentence.  
>>
>> Sorry, I mean this (let me draw :) ) :
>>
>> [ page 0 ][ page 1 ][ page 2 ][ page 3 ][ page 4 ][ page 5 ][ page 6 ][ page 7 ][ page 8 ][ page 9 ]
>>
>> For example, we have 10 pages starting from the beginning of the chip - this is "within specified offset",
>> e.g. offset is 10. BootROM on axg needs that (for example) every third page must be written in "special"
>> mode: scrambling is on and ECC is 384 bytes. Such pages are 0, 2, 4, 6, 8. E.g. "specified interval" will
>> be 3.
> 
> Shall be 2, no?

yes, starting from 0 - then 2. e.g.
if (!(page_num % 2))
    boot ROM need this page

> 
>>
>> So:
>>
>> amlogic,boot-pages: 10
>> amlogic,boot-page-step: 3
> 
> Ok I get it. Thanks for the explanation. I don't really understand the
> logic behind it though. Do you know why the bootROM would access only
> one page over 2 or 3? Is there a default value? Is this configurable?

No, boot rom source is closed, I don't have access to it. I get this logic
from old version of vendor's uboot - in practice they use non 2 or 3, they
use hardcoded 128 step value. And amlogic,boot-pages is 1024

Thanks, Arseniy

> 
> Thanks,
> Miquèl