The common CFI driver provides this weak default implementation for
  flash_cmd_reset():
  
  static void __flash_cmd_reset(flash_info_t *info)
  {
  	/*
  	 * We do not yet know what kind of commandset to use, so we issue
  	 * the reset command in both Intel and AMD variants, in the hope
  	 * that AMD flash roms ignore the Intel command.
  	 */
  	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
  	udelay(1);
  	flash_write_cmd(info, 0, 0, FLASH_CMD_RESET);
  }
  void flash_cmd_reset(flash_info_t *info)
  	__attribute__((weak,alias("__flash_cmd_reset")));
  
  Some flash chips seem to have trouble with this reset sequence.
  In this case, board-specific code can override this weak default
  version with a board-specific function.
  
  At the time of writing, there are two boards that define their own
  routine for this.
  
  First, the digsy_mtc board equipped with the M29W128GH from Numonyx
  needs this version to function properly:
  
  void flash_cmd_reset(flash_info_t *info)
  {
  	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
  }
  
  In addition, the t3corp board defines the routine thusly:
  
  void flash_cmd_reset(flash_info_t *info)
  {
  	/*
  	 * FLASH at address CONFIG_SYS_FLASH_BASE is a Spansion chip and
  	 * needs the Spansion type reset commands. The other flash chip
  	 * is located behind a FPGA (Xilinx DS617) and needs the Intel type
  	 * reset command.
  	 */
  	if (info->start[0] == CONFIG_SYS_FLASH_BASE)
  		flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
  	else
  		flash_write_cmd(info, 0, 0, FLASH_CMD_RESET);
  }
  
  see also:
  http://www.mail-archive.com/u-boot@lists.denx.de/msg24368.html
  
  
  Config Option
  
    CONFIG_SYS_MAX_FLASH_SECT: Number of sectors available on Flash device
  
    CONFIG_SYS_FLASH_CFI_WIDTH: Data-width of the flash device
  
    CONFIG_CMD_FLASH: Enables Flash command library
  
    CONFIG_FLASH_CFI_DRIVER: Enables CFI Flash driver
  
    CONFIG_FLASH_CFI_MTD: Enables MTD frame work for NOR Flash devices