[Help] I want to know how to make an image for w25q256JV flash memory.

[Patrick Williams]

On Mon, Mar 07, 2022 at 12:00:42PM +0900, pooky at sysmate.com wrote:
 
> I am developing a motherboard using AST2500 chip using openbmc. 
> It is booting with w25q256JV flash memory attached to the AST2500 chip.
> I want to know how to make an image for w25q256JV flash memory.

That chip is relatively small for our codebase (32MB).  We still have some
machines running that size but we typically have to reduce the features in order
to make it fit.

Building an image doesn't really concern itself with the particular model of
chip but the size.  The more important thing for your system is all the
configuration information you need to provide about your motherboard so that the
software knows how to operate the hardware.

In our repository you'll see a lot of 'meta-*' subdirectories.  Most of these
are the Yocto layers for machines designed by various companies.  These are the
configuration data on those machines.  You may want to take one that looks
similar in design and start with that.

Specifically on your question regarding this chip, the only thing we really need
configured is the FLASH_SIZE variable.  This will build the 32MB image that can
fit into your chip.  Nothing else should care about the specific model because
u-boot and Linux should use the JEDEC model information to determine the size of
that chip when they access it.  Here are a number of machines configured with a
32MB flash layout:

```
$ git grep 'FLASH_SIZE = "32768"'
meta-amd/meta-ethanolx/conf/machine/ethanolx.conf:FLASH_SIZE = "32768"
meta-asrock/meta-e3c246d4i/conf/machine/e3c246d4i.conf:FLASH_SIZE = "32768"
meta-facebook/meta-tiogapass/conf/machine/tiogapass.conf:FLASH_SIZE = "32768"
meta-facebook/meta-yosemitev2/conf/machine/yosemitev2.conf:FLASH_SIZE = "32768"
meta-ibm/meta-palmetto/conf/machine/palmetto.conf:FLASH_SIZE = "32768"
meta-inspur/meta-on5263m5/conf/machine/on5263m5.conf:FLASH_SIZE = "32768"
meta-intel-openbmc/meta-s2600wf/conf/machine/s2600wf.conf:FLASH_SIZE = "32768"
meta-nuvoton/conf/machine/evb-npcm750.conf:FLASH_SIZE = "32768"
meta-quanta/meta-gsj/conf/machine/gsj.conf:FLASH_SIZE = "32768"
meta-quanta/meta-olympus-nuvoton/conf/machine/olympus-nuvoton.conf:FLASH_SIZE = "32768"
meta-quanta/meta-q71l/conf/machine/quanta-q71l.conf:FLASH_SIZE = "32768"
meta-supermicro/meta-x11spi/conf/machine/x11spi.conf:FLASH_SIZE = "32768"
meta-tyan/meta-s7106/conf/machine/s7106.conf:FLASH_SIZE = "32768"
meta-tyan/meta-s8036/conf/machine/s8036.conf:FLASH_SIZE = "32768"
```

-- 
Patrick Williams
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