[U-Boot-Users] u-boot CFI driver question

[Martin Krause]

Hi,

u-boot-users-bounces at lists.sourceforge.net wrote on Wednesday, October
24, 2007 9:58 PM: 
> I am attempting to bring up a board with u-boot. I've so far been
> able to get 
> u-boot far enough along to get to the main prompt. I am having an
> issue 
> reading from and writing to the FLASH memory in my setup. For
> simplicity 
> sake my setup consists of an ARM920T processor, EEPROM (AM29040B) and
> 2 
> FLASH devices (S29GL256N...). U-boot resides in the EEPROM and I am
> able to 
> read/write to the EEPROM.
> 
> My non-EEPROM FLASH configuration consists of two devices. Both
> devices have 23 address pins and 16 data pins. I have routed the 23
> address pins of the 
> ARM to both FLASH devices. However, I have routed the ARM’s lower 16

Since you have a 32 bit data bus, you didn't connect the address
lines A0 and A1 to your flash, did you (you mentioned you've
connected all 23 address lines, which would propably be wrong)?

> data 
> pins to one device and its upper 16 data pins to the second device.
> On paper 
> this should give me 8 Meg locations of 32 bits for a total of 32 Megs
> of 
> FLASH.

The S29GL256N is a 256 MBit type. So you get 16M x 16 Bit x 2 (Chips)
= 64 MByte Flash. If your cpu only has address lines A0 to A23, this
is maybe too less to access 64 MByte of Flash (it depends, on how
you could configure your bus interface). Normally you need the
address lines A0 to A25 and connect A2 to A25 to your Flash:
A2 (cpu) -> A0 (flash), A3 -> A1, ...

> I have compiled u-boot to include the CFI driver. I am pretty certain
> that I 
> have setup the ARM through u-boot to use the proper chip select and
> address/data bus. I believe this because when I issue an erase
> command from 
> the u-boot prompt I can see the correct chip select toggle and I see
> the 
> correct address and data pins wiggling.
> 
> My issue seems to be when I try to read/write to the FLAHS devices.
> For 
> example, when I issue the erase command u-boot spits back an error
> message. Unfortunately, I am not able to tell you the exact error
> message at the 
> moment and I cannot remember the exact phrase.

Hm, you should be possible to reproduce the error messag by simply
issuing the erase command again on the u-boot prompt, no?

> Error message aside I suspect that I am have a problem because I have
> not 
> informed u-boot of this configuration. So my questions are:
> 
> 1) Does u-boot inherently support a setup with a 32 bit data bus split
> across two devices?

Yes. If your hardware is configured correctliy, it should be transparent
to U-Boot.

> 2) If so can someone point me to an example configuration file in
> u-boot to 
> get the cfi driver properly configured?

The cfi driver dont't need to be configured. It should be able to
detect your flash memory.

> 3) If not, has someone patched u-boot to handle this configuration?

This is a very common board configuration (the TQM5200 board uses
this configuration for example).

Best Regards,
Martin Krause

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