[[PageOutline]]

= Alternate Boot Device
Some Gateworks family products have an 'Alternate boot device' that can be used for alternate firmware images, such as a flash recovery image:
 * Newport - eMMC (primary) vs microSD (alternate)

[=#auto-switch-boot]
== Auto Switch Boot Device
The [wiki:gsc Gateworks System Controller] implements an 'Auto Switch Boot Device' feature that can be useful as a firmware recovery mechanism. GSC register R1.6 (SWITCH_BOOT_ENABLE) enables this mode. When this is set and the board powers on it will initiate a countdown timer cleared by the boot firmware that expires in 30 seconds. Therefore if the boot firmware is missing/corrupt the board will power cycle and boot off the alternate device.

To enable from Linux:
{{{#!bash
i2cset -f -y 0 0x20 1 0x40      ;# enable R1.6 (SWITCH_BOOT_ENABLE)
}}}

To enable from u-boot
{{{#!bash
i2c dev 0 && i2c mw 0x20 1 0x40 1     ;# enable R1.6 (SWITCH_BOOT_ENABLE)
}}}

== Current Boot Device
The current boot device is held in GSC register R21 (0x15) with a value of 0 being primary and a value of 1 being alternate. This value will be toggled by the 'Auto Switch Boot' feature [wiki:gsc/alternate_boot_device#auto-switch-boot above] but can also be manually set:

From Linux:
 * Alternate
{{{#!bash
i2cset -f -y 0 0x20 0x15 1 # set boot device to 1 (alternate)
}}}
 * Primary
{{{#!bash
i2cset -f -y 0 0x20 0x15 0 # set boot device to 0 (primary)
}}}

U-Boot:
 * Alternate:
{{{#!bash
i2c dev 0 && i2c mw 0x20 0x15 1 # set boot device to 1 (alternate)
}}}
 * Primary:
{{{#!bash
i2c dev 0 && i2c mw 0x20 0x15 0 # set boot device to 0 (primary)
}}}