[U-Boot] U-boot running on DDR fails to detect the CFI compliant flash

[Jerry Van Baren <gerald.vanbaren@ge.com>]

Stefan Roese wrote:
> On Tuesday 19 January 2010 07:24:10 prakash bedge wrote:
>> I have tried the code in the URL link you have provided. But still I am
>> facing the same problem. I am getting the error in "flash_detect_cfi" as
>> flash not found. It fails at initial stage at read CFI query command.
>> The code you have provided is for M29W128GL.(Numonix). Will this work for
>> M29W128GH (STMIcrotronics)?
> 
> Frankly, I don't know. You need to check the datasheets, to see if there are 
> some differences.
> 
>> I believe Uboot support M29W128GH flash. I am using this flash chip in 16 x
>> 8 bit mode.
>> The URL I provided is available under the thread:
>> "[U-Boot] Query: Does Uboot support CFI flash driver forM29W128GH".
>> Can there be an endianness issue, as I am running uboot from SDRAM and in
>> Big endian mode?
> 
> No, I don't think that this is an endian issue. All PPC4xx platforms are doing 
> it the same way. This must be a different problem.
> 
> Did you check that the NOR chip is really selected (chip select signal etc on 
> the FLASH chip via oscilloscope)? Are the addresses correct for the query 
> (etc) commands?
> 
> Cheers,
> Stefan

IIRC, Prakash added debug print statements that showed the "Q" of the 
"QRY" being read, but did not show anything more.  As a result, it was 
impossible to tell why the CFI detect was not working.

What I find is *VERY* helpful when trying to understand flash control 
issues is to *manually* do the QRY write sequence (see your flash data 
sheet) by using memory write/read commands from the u-boot command 
prompt.  This way I can quickly try different byte widths, lanes, etc. 
for the writes and see the full QRY response from the memory.  Usually 
the problem is a simple misunderstanding of how the chip is configured 
or the hardware is wired (beware of hardware designers doing "endian 
fixes").

Good luck,
gvb