[U-Boot-Users] is there a bug in cfi_flash.c

[Yuli Barcohen]

    Yusuf> There might be a bug in the code for reading status register
    Yusuf> in cfi_flash driver.  In the function "flash_isset" it's
    Yusuf> directly read as reading from memory. But in intel's data
    Yusuf> sheet (for 28F640C3T) reading status register is described as
    Yusuf> below.

    Yusuf>     Read Status Register

    Yusuf>     The status register indicates the status of device
    Yusuf>     operations, and the
    Yusuf> success/failure of that

    Yusuf>     operation. The Read Status Register (0x70) command causes
    Yusuf>     subsequent
    Yusuf> reads to output data from

    Yusuf>     the status register until another command is issued. To
    Yusuf>     return to
    Yusuf> reading from the array, issue a

    Yusuf>     Read Array (0xFF) command.

    Yusuf> So before reading for SR, "Read Status Register" (0x70)
    Yusuf> command must be written to the flash.

After write/erase/protect operations, flash is already in "read status"
mode so no additional command is necessary.

    Yusuf> But I think this driver is beeing used by several boards. So
    Yusuf> if this driver is tested and it's working, I should be
    Yusuf> missing something?

On Intel flashes, it's very simple to issue commands and see results by
using md/mw U-Boot commands. You are trying to unprotect sector at
0xFF000000. So try:

  md ff000000
  mw.l ff000000 60606060
  mw.l ff000000 d0d0d0d0
  md ff000000

First md should show the flash contents, second md should show status on
one half of the bus (80808080 if there were no errors) and the flash
contents on another half. If this does not work, you either have got
flash write access problem (check the WE# line) or the flash must be
accessed by single 64-bit write. In the latter case, CFI driver won't
work.

-- 
========================================================================
 Yuli Barcohen       | Phone +972-9-765-1788 |  Software Project Leader
 yuli at arabellasw.com | Fax   +972-9-765-7494 | Arabella Software, Israel
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