Re: support for non-uniform SPI NOR flash memories

[Marek Vasut <marek.vasut@gmail.com>]

On 05/09/2018 06:40 PM, Tudor Ambarus wrote:
> 
> On 05/07/2018 08:14 PM, Marek Vasut wrote:
>> But indeed there are -- to my knowledge -- no flashes with interleaved
>> erase blocks. And yes, there could be improvement in erasing exactly the
>> required chunk of flash with a fitting opcode:)
> 
> Thanks Marek.
> 
> Other improvement would be to minimize the amount of erase() calls by
> using the best sequence of erase type commands depending on alignment.
> But this will increase the number of queries.
> 
> I've read again the Sector Map section of the JEDECB standard and it
> looks like "overlaid" regions are possible. Here's an example that I
> found there:
> 
> Bottom: 8x 4KB sectors at bottom (only 4KB erase supported),
>         1x overlaid 64KB sector at bottom (only 64KB erase supported),
>         511 uniform 64KB sectors (only 64KB erase supported)
> 
> That's interesting, when one wants to erase the overlaid 64KB sector, I
> guess that the 8x 4KB sectors will be erased too.

Ah yes, some old flashes had these few 64 kiB erase blocks at the
beginning/end, which could either be erased as one 64 kiB block or as
smaller 8k/4k blocks .

> I'm still studying this, I'll try to come with a proposal in the next
> few days.

Cool!

-- 
Best regards,
Marek Vasut