[U-Boot] framework for serial flash

[ashish priyadarshi]

Hello Wolfgang

Thanks for your reply.

The device composes of a Serial NOR flash (STmicro M25P64) and Serial Memory

Controller Interface (SMI). All operations such as Read-ID, read-data,
write-data, and
erase can be controlled by SMI. Like for Read-ID, first command is written
into the TX
register of SMI and then 3 bytes of flash-ID can be read back from Rx
regsiter of SMI.

SMI differs from a normal SPI controller in this way that it manages a lot
of things
on its own. For example to  read FLASH id we need to tell SMI beforehand how
many
bytes it has to read in response to this command.
The SPI Flash interface however splits this in two seperate xfer calls where
command
is sent first and then response is read.
regards
Ashish

On Thu, Nov 12, 2009 at 3:02 AM, Wolfgang Denk <wd at denx.de> wrote:

> Dear ashish priyadarshi,
>
> In message <fb24d2790911102234x4d210e10mdd9d551541120dc0 at mail.gmail.com>
> you wrote:
> >
> > We have a special "Serial flash controller" which was put into the
> standard
> > flash
> > framework of uboot (common/cmd_flash.c). Commands like 'cp', 'erase'
> could
> > be
> > used for operation over serial flash.
>
> What do you mean by "Serial flash controller"? Some storage device
> similar to NAND or SPI Flash? This would not fit, then.
>
> > Since we felt "Serial flash controller" resembles SPI flash framework,
> and
> > hence
> > decided to move it there. Problem is that this "Serial flash controller"
> is
> > also not
> > fitting in SPI framework because of its nature.
>
> So you already learned that your serial flash is not a type of memory,
> but a storage device. You cannot use the memory interface as used for
> NOR flash for it.
>
> > How to handle such situations, is there any other framework or we need to
> > introduce
> > our own commands? We are using "u-boot-2009.08".
>
> That's difficult to impossible to answer - you don't provide any
> information what exact sort of device you have or why it would (not)
> fit into the SPI flash code.
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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