| The Korat board has two NOR flashes, FLASH0 and FLASH1, which are connected to |
| chip select 0 and 1, respectively. FLASH0 contains 16 MiB, and is mapped to |
| addresses 0xFF000000 - 0xFFFFFFFF as U-Boot Flash Bank #2. FLASH1 contains |
| from 16 to 128 MiB, and is mapped to 0xF?000000 - 0xF7FFFFFF as U-Boot Flash |
| Bank #1 (with the starting address depending on the flash size detected at |
| runtime). The write-enable pin on FLASH0 is disabled, so the contents of FLASH0 |
| cannot be modified in the field. This also prevents FLASH0 from executing |
| commands to return chip information, so its configuration is hard-coded in |
| U-Boot. |
| |
| There are two versions of U-Boot for Korat: "permanent" and "upgradable". The |
| permanent U-Boot is pre-programmed at the top of FLASH0, e.g., at addresses |
| 0xFFFA0000 - 0xFFFFFFFF for the current 384 KiB size. The upgradable U-Boot is |
| located 256 KiB from the top of FLASH1, e.g. at addresses 0xF7F6000 - 0xF7FC0000 |
| for the current 384 KiB size. FLASH1 addresses 0xF7FE0000 - 0xF7FF0000 are |
| used for the U-Boot environmental parameters, and addresses 0xF7FC0000 - |
| 0xF7FDFFFF are used for the redundant copy of the parameters. These locations |
| are used by both versions of U-Boot. |
| |
| On booting, the permanent U-Boot in FLASH0 begins executing. After performing |
| minimal setup, it monitors the state of the board's Reset switch (GPIO47). If |
| the switch is sensed as open before a timeout period, then U-Boot branches to |
| address 0xF7FBFFFC. This causes the upgradable U-Boot to execute from the |
| beginning. If the switch remains closed thoughout the timeout period, the |
| permanent U-Boot activates the on-board buzzer until the switch is sensed as |
| opened. It then continues to execute without branching to FLASH1. The effect |
| of this is that normally the Korat board boots its upgradable U-Boot, but, if |
| this has been corrupted, the user can boot the permanent U-Boot, which can then |
| be used to erase and reload FLASH1 as needed. |
| |
| Note that it is not necessary for the permanent U-Boot to have all the latest |
| features, but only that it have sufficient functionality (working "tftp", |
| "erase", "cp.b", etc.) to repair FLASH1. Also, the permanent U-Boot makes no |
| assumptions about the size of FLASH1 or the size of the upgradable U-Boot: it is |
| sufficient that the upgradable U-Boot can be started by a branch to 0xF7FBFFFC. |
| |
| The build sequence: |
| |
| make korat_config |
| make all perm=1 |
| |
| builds the permanent U-Boot by selecting loader file "u-boot.lds" and defining |
| preprocessor symbol "CONFIG_KORAT_PERMANENT". The default build: |
| |
| make korat_config |
| make all |
| |
| creates the upgradable U-Boot but selecting loader file "u-boot-F7FC.lds" and |
| leaving preprocessor symbol "CONFIG_KORAT_PERMANENT" undefined. |
| |
| 2008-02-22, Larry Johnson <lrj@acm.org> |
| |
| |
| The CompactFlash(R) controller on the Korat board provides a hi-speed USB |
| interface. This may be connected to either a dedicated port on the on-board |
| USB controller, or to a USB port on the PowerPC 440EPx processor. The U-Boot |
| environment variable "korat_usbcf" can be used to specify which of these two |
| USB host ports is used for CompactFlash. The valid setting for the variable are |
| the strings "pci" and "ppc". If the variable defined and set to "ppc", then the |
| PowerPC USB port is used. In all other cases the on-board USB controller is |
| used, but if "korat_usbcf" is defined but is set to a string other than the two |
| valid options, a warning is also issued. |
| |
| 2009-01-28, Larry Johnson <lrj@acm.org> |
