[U-Boot] mtd/cfi: SST39VF3201B flash model not properly handled

[U-Boot] mtd/cfi: SST39VF3201B flash model not properly handled

[Angelo Dureghello]

Dear All,

as Wolfgang Denx suggested me, i am trying to use the u-boot CFI driver with 
a CFI flash (SSTVF3201B).

This flash chip allows erasing/writing blocks of 4 KBytes (called "sectors" 
in the SST datasheet), or 64 KBytes (called "blocks"). 

The command sequence table for this flash shows 2 different commands to 
operate on these 2 kind of blocks. 0x50 is for "sector erase" and "0x30" (the
command used from u-boot CFI driver as AMD_CMD_ERASE_SECTOR) is for the
64KB "block" erase.

The issue:
now, u-boot CFI driver works fine on 64KB boundary ranges, but if i expect
to erase a 4KB sector size i get a full 64KB block erased. 

Proposed solution:
Initially, a single sector size definition would be good enough for this chip, 
so the user should specify if he wants a 64 or 4 KB sector to be used, using
some CFG_X.
CFI driver, through queries, should be able to identify this particular chip
so that it can be handled in a specific way from the CFI driver (cmd 0x50 for
4KB secotrs, or 0x30 for 64KB secotrs).

I am thinking about to post a patch on this.
Anyway, until new AMCORE board patch is not accepted, there is the chance 
this can result as a "dead code" if no-one use this flash chip except me.
 
So, before i start, please let me know how to proceed, maybe is better to use
a specific flash.c for my board for now ? 
Or if you think a patch can be useful, any suggestion on how to implement it 
is really welcome.


Best Regards,
Angelo Dureghello

[U-Boot] mtd/cfi: SST39VF3201B flash model not properly handled

[Stefan Roese]

Hi Angelo,

On 11/29/2012 01:03 PM, Angelo Dureghello wrote:
> as Wolfgang Denx suggested me, i am trying to use the u-boot CFI driver with 
> a CFI flash (SSTVF3201B).

Yes. But please take a look at the CONFIG_FLASH_CFI_LEGACY config
option. This enables the legacy CFI flash devices. And IIRC the SST
flash chips are supported via this driver/extension.

> This flash chip allows erasing/writing blocks of 4 KBytes (called "sectors" 
> in the SST datasheet), or 64 KBytes (called "blocks"). 
> 
> The command sequence table for this flash shows 2 different commands to 
> operate on these 2 kind of blocks. 0x50 is for "sector erase" and "0x30" (the
> command used from u-boot CFI driver as AMD_CMD_ERASE_SECTOR) is for the
> 64KB "block" erase.
> 
> The issue:
> now, u-boot CFI driver works fine on 64KB boundary ranges, but if i expect
> to erase a 4KB sector size i get a full 64KB block erased. 
> 
> Proposed solution:
> Initially, a single sector size definition would be good enough for this chip, 
> so the user should specify if he wants a 64 or 4 KB sector to be used, using
> some CFG_X.
> CFI driver, through queries, should be able to identify this particular chip
> so that it can be handled in a specific way from the CFI driver (cmd 0x50 for
> 4KB secotrs, or 0x30 for 64KB secotrs).
> 
> I am thinking about to post a patch on this.
> Anyway, until new AMCORE board patch is not accepted, there is the chance 
> this can result as a "dead code" if no-one use this flash chip except me.
>  
> So, before i start, please let me know how to proceed, maybe is better to use
> a specific flash.c for my board for now ? 
> Or if you think a patch can be useful, any suggestion on how to implement it 
> is really welcome.

Please see my comment above. And grep for CONFIG_FLASH_CFI_LEGACY to see
how its used in the config header. And if necessary, you can always
extend the CFI configuration in the JEDEC source:

drivers/mtd/jedec_flash.c

Thanks,
Stefan

[U-Boot] mtd/cfi: SST39VF3201B flash model not properly handled

[Angelo Dureghello]

Dear Stefan Roese,

> > as Wolfgang Denx suggested me, i am trying to use the u-boot CFI driver with 
> > a CFI flash (SSTVF3201B).
> 
> Yes. But please take a look at the CONFIG_FLASH_CFI_LEGACY config
> option. This enables the legacy CFI flash devices. And IIRC the SST
> flash chips are supported via this driver/extension.
> 

> > This flash chip allows erasing/writing blocks of 4 KBytes (called "sectors" 
> > in the SST datasheet), or 64 KBytes (called "blocks"). 
> > 
> > The command sequence table for this flash shows 2 different commands to > 
> Please see my comment above. And grep for CONFIG_FLASH_CFI_LEGACY to see
> how its used in the config header. And if necessary, you can always
> extend the CFI configuration in the JEDEC source:
> 
> drivers/mtd/jedec_flash.c
 
thaks for the hint, anyway seems i am unfortunate whit this flash chip:

first of all, i would understand why a flash chip is defined/handled as 
leagacy. Can someone kindly clarify this ? SST39VF3201B is a 2M x 16, 
CFI compliant.

CFI legacy dont seems anyway to support 0x50 command for erasing a sector, 
i grepped and found "only" a CMD_CLEAR_STATUS as 0x50 that don't seems to fit
the case. But the code is not trivial, and i can miss something of course.

Also, legacy flash_info_t don't have any field to define the erase sector
command. But still, i am not sure this chip should be considered legacy.

I grepped for *3201* SST chip, only baord that seems to use it is 

esd/common

and this board has her own flash.c

But still, has been suggested me to use CFI driver, so i need to know what
the u-boot community would prefer as approach.

Still a note. I found issues in Linux also for this chip (STT39VF3201B) and
had to ask for a patch on the command set to allow the correct erase command 
to be used.

So how should i proceed ?

Many thanks.

Best Regards
Angelo Dureghello