| 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_perm_config | |
| make all | |
| 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 by 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> |