[OpenWrt-Devel] Rebooting boards with > 16M SPI flash

Arjen de Korte arjen+openwrt at de-korte.org
Thu Jul 9 03:30:36 EDT 2015

Citeren Paul Fertser <fercerpav at gmail.com>:

> Hi John,
> John Crispin <blogic at openwrt.org> writes:
>> looks good to me but i will run this past linux-mtd and ask them for an
>> opinion before merging it.
> This patch was meant as a quick "hack" rather than a complete solution,
> that's why I didn't bother adding proper commit message, S-o-b etc. But
> since I'm the author, I can do that promptly, whenever that's needed.
> The main limitation is that I checked only a single datasheet (likely
> Winbond) so other models might require different treatment.

The way to exit 4-byte addressing mode, can be determined by looking  
at the SFDP (JEDEC Standard JESD216B). As you already suspected, there  
are many possibilities. The method required, can be derived from the  
16th DWORD from the JEDEC Basic Flash Parameter Table (page 28).

> Another is
> that such a patch is mostly a bad substitute for proper hardware design.

Not really. There may not be a hardware reset line if the flash is  
running in x4 data mode.

Regards, Arjen
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