| ROM-able zImage boot from eSD |
| ----------------------------- |
| |
| An ROM-able zImage compiled with ZBOOT_ROM_SDHI may be written to eSD and |
| SuperH Mobile ARM will to boot directly from the SDHI hardware block. |
| |
| This is achieved by the mask ROM loading the first portion of the image into |
| MERAM and then jumping to it. This portion contains loader code which |
| copies the entire image to SDRAM and jumps to it. From there the zImage |
| boot code proceeds as normal, uncompressing the image into its final |
| location and then jumping to it. |
| |
| This code has been tested on an mackerel board using the developer 1A eSD |
| boot mode which is configured using the following jumper settings. |
| |
| 8 7 6 5 4 3 2 1 |
| x|x|x|x| |x|x| |
| S4 -+-+-+-+-+-+-+- |
| | | | |x| | |x on |
| |
| The eSD card needs to be present in SDHI slot 1 (CN7). |
| As such S1 and S33 also need to be configured as per |
| the notes in arch/arm/mach-shmobile/board-mackerel.c. |
| |
| A partial zImage must be written to physical partition #1 (boot) |
| of the eSD at sector 0 in vrl4 format. A utility vrl4 is supplied to |
| accomplish this. |
| |
| e.g. |
| vrl4 < zImage | dd of=/dev/sdX bs=512 count=17 |
| |
| A full copy of _the same_ zImage should be written to physical partition #1 |
| (boot) of the eSD at sector 0. This should _not_ be in vrl4 format. |
| |
| vrl4 < zImage | dd of=/dev/sdX bs=512 |
| |
| Note: The commands above assume that the physical partition has been |
| switched. No such facility currently exists in the Linux Kernel. |
| |
| Physical partitions are described in the eSD specification. At the time of |
| writing they are not the same as partitions that are typically configured |
| using fdisk and visible through /proc/partitions |
