Programming the Flash

=================================================================================
from: http://developer.petalogix.com/wiki/UserGuide/Bootloaders/UBoot/UsingUBoot/UBProgFlash

Programming the Flash ¶

menu

• User Guide

• Copyright Information
• Acknowledgements
• Terminology
• Introduction

• PetaLinux Overview...

• Working with PetaLinux - The Basics...

• Customising PetaLinux...

• Advanced Topics...

• Debugging...

• PetaLinux Bootloader Solutions

• First Stage Boot (FS-Boot)...

• U-Boot

• Overview
• Adding U-Boot
• Building U-Boot
• Customizing U-Boot

• Using U-Boot

• Booting U-Boot
• Downloading Files
• Programming Flash
• Platform Initialisation
• Erase U-Boot Environment
• Updating Ethernet MAC Address in U-Boot

• Supported Reference Designs...

• PetaLinux Tools Reference
• Getting Help

Flash memory is a form of non-volatile memory that can be erased and reprogrammed. Normally flash is used to store the U-Boot image, U-Boot environment variables and the kernel image. In order to update the content of flash, the designer must know how to reprogram the flash.

U-Boot Flash Commands ¶

U-Boot offers several commands for programming, erasing and protecting the flash memory. This section will provide guidelines on how to use these commands.

Flash information ¶

Prior to accessing the Flash device, the device information such as device size, erase block size and memory mapped addresses is often required. The 'flinfo' command in U-Boot allows the user to obtain such information.

U-Boot>  flinfo
Bank # 1: CFI conformant FLASH (32 x 16)  Size: 8 MB in 32 Sectors
 Erase timeout 16384 ms, write timeout 3 ms, buffer write timeout 3 ms, buffer size 32
  Sector Start Addresses:
    28000000 (RO) 28040000 (RO) 28080000      280C0000      28100000     
    28140000      28180000      281C0000      28200000      28240000     
    28280000      282C0000      28300000      28340000      28380000     
    283C0000      28400000      28440000      28480000      284C0000     
    28500000      28540000      28580000      285C0000      28600000     
    28640000      28680000      286C0000      28700000      28740000     
    28780000      287C0000     
U-Boot> 

The output carries quite a lot of information, e.g flash sector layout, sector start addresses. For this particular flash chip it contents 32 256KB sectors start at address 0x28000000 for a total of 8MB.

Unlock Protected Flash Sectors ¶

The sectors following (RO) indicate that this sector is "protected". In this example sectors, sector 0 contains U-Boot image and sector 1 is used to store the U-Boot environment variables. Any attempt to program these sectors without first unlocking them will fail.

Use U-Boot 'protect' command to unlock the protected flash sectors. Two additional parameters are required for the 'protect' command. They include the on/off option (to switch on/off the protection) and the particular bank and sector to unprotect.

protect off :

To turn off flash protection of sector 0 in bank 1.

u-boot # protect off 1:0
Un-Protect Flash Sectors 0-0 in Bank # 1

Note: The parameter can be a range of sectors, e.g sector 3 to 18 can be represent in 3-18

Erase Flash Sectors ¶

Use U-Boot 'erase' command to erase flash sectors. Similar to the 'protect' command, the 'erase' command requires the bank number and sector number information.

erase :

To erase flash sector 0 of flash bank 1.

U-Boot> erase 1:0
Erase Flash Sectors 0-0 in Bank # 1 
. done

Program the Flash ¶

The byte version of the 'cp' command (cp.b)is used to program the flash memory. The 'cp.b' command requires three parameters, the copy-from address, copy-to address and size. The cp command will automatically detect if it is accessing Flash memory, if so it will use the appropriate Flash programming routine to program the Flash device. However, the user is required to unprotect and/or erase the Flash area before programming it.

cp.b   

Note that the '' value is given in hexidecimal and is the number of units (.b for bytes etc.) to copy.

The above step will attempt to program the kernel image into the Flash device, depending on the Flash device used this step may take a while to complete. Note that the U-Boot cp command do not provide status information for the copy process.

The following example downloads a new U-Boot image file (u-boot-s.bin) into U-Boot's memory. Refer to the of the User Guide for more information.

Filename 'u-boot-s.bin'.
Load address: 0x10000000
Loading: #######################
done
Bytes transferred = 116884 (1c894 hex)

Note the "Load address and Bytes transferred" of the downloaded file. In the above example, it is 0x10000000 and 0x1c894 respectively. These values will be required when reprogramming the Flash device.

The below example will copy the image in RAM into the Flash partition.

U-Boot> cp.b 0x10000000 0x28000000 0x1c894
Copy to Flash... done

Restore Protection ¶

Use U-Boot 'protect' command to re-enable protection of the particular Flash sectors.

protect on :

To restore flash protection of sector 0 in bank 1.

U-Boot> protect on 1:0
Protect Flash Sectors 0-0 in Bank # 1

Reboot the system to run the newly uploaded U-Boot code.