[U-Boot] [PATCH] flread: new command for reading indirect mapped flashes

Mike Frysinger
2009-07-06T08:37:10Z

On Monday 06 July 2009 03:25:43 Stefan Roese wrote:
> On Monday 06 July 2009 09:04:44 Mike Frysinger wrote:
> > > I kind of like the idea to create a new set of commands for accessing
> > > such board specific NOR FLASH (can be used on "normal" NOR FLASH as
> > > well). Perhaps we could make it "generic" in a way that it can be used
> > > for all kind of "MTD devices". How about this "mtd" commandset:
> > >
> > > Select MTD NOR device #1 (2nd NOR device):
> > > => mtd device nor 1
> > >
> > > Or via mtdparts/mtdids:
> > > => mtd device nor0
> >
> > so both syntaxes would be available when mtdparts support is enabled, or
> > would it be one or the other ?
>
> I didn't make my mind up until now. I was just throwing out an idea.
>
> > we would want to avoid ambiguity -- is
> > "nor" referring to the nor flashes or is it referring to a partition
> > named "nor".
>
> The first version would refer "nor" as flash type and the 2nd one "nor0" as
> a device name from mtdparts/mtdids.

so people wouldnt be able to name a mtdpart "nor"

> > what flash devices does mtdparts support now ? i'm not really familiar
> > with it and the README and doc/ files doesnt seem to cover it.
>
> Right now it supports NAND, OneNAND and NOR (if CONFIG_FLASH_CFI_MTD is
> enabled). Others can be easily added (see drivers/mtd/cfi_mtd.c for NOR).

so FLASH_CFI_MTD is merely glue between the existing CFI flash driver and the
MTD layers ?

> > i guess each flash type would parse the additional commands however it
> > liked and so the mtd command would just act as a multiplexer at this
> > point. the current spi flash "sf" command is pretty flexible -- you
> > specify the spi chip select to select the device and you can specify
> > other parameters dynamically (like frequency). so when folding it in,
> > we'd have: => mtd device sf <cs> [speed] [mode]
> >
> > common/cmd_mtd.c
> > common/cmd_mtd_sf.c
> > common/cmd_mtd_nor.c
>
> I was more thinking about adding the MTD layer to all FLASH types supported
> by this new commandset. Then accessing the device is done via the MTD
> functions pointers (mtd->erase, mtd->read, etc). Special FLASH type
> specific stuff still needs to be handled in some additional drivers (like
> OOB handling for NAND/OneNAND, or SF specific stuff) though.

ok, this seems like it should be doable in a gradual progression. i.e. today
i am only concerned with nor flash, so getting a base framework with that as
the only supported flash should be fine. once we know it can replace the
existing cmd_flash.c functions, we can look at folding in other flash types.
-mike
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