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# Flashing firmware tutorial
Updating the firmware is possible using the **internal method**, where the updates
happen from a running system, or using the **external method**, where the system
is in a shut down state and an external programmer is attached to write into the
flash IC.
## Contents
* [Flashing internally](int_flashrom.md)
* [Flashing firmware standalone](ext_standalone.md)
* [Flashing firmware externally supplying direct power](ext_power.md)
* [Flashing firmware externally without supplying direct power](no_ext_power.md)
## General advice
* It's recommended to only flash the BIOS region.
* Always verify the firmware image.
* If you flash externally and have transmission errors:
* Use short wires
* Reduce clock frequency
* Check power supply
* Make sure that there are no other bus masters (EC, ME, SoC, ...)
## Internal method
This method using [flashrom] is available on many platforms, as long as they
aren't locked down.
There are various protection schemes that make it impossible to modify or
replace a firmware from a running system. coreboot allows to disable these
mechanisms, making it possible to overwrite (or update) the firmware from a
running system.
Usually you must use the **external method** once to install a retrofitted
coreboot and then you can use the **internal method** for future updates.
There are multiple ways to update the firmware:
* Using flashrom's *internal* programmer to directly write into the firmware
flash IC, running on the target machine itself
* A proprietary software to update the firmware, running on the target machine
itself
* A UEFI firmware update capsule
More details on flashrom's
* [internal programmer](int_flashrom.md)
## External method
External flashing is possible on many platforms, but requires disassembling
the target hardware. You need to buy a flash programmer, that
exposes the same interface as your flash IC (likely SPI).
Please also have a look at the mainboard-specific documentation for details.
After exposing the firmware flash IC, read the schematics and use one of the
possible methods:
* [Flashing firmware standalone](ext_standalone.md)
* [Flashing firmware externally supplying direct power](ext_power.md)
* [Flashing firmware externally without supplying direct power](no_ext_power.md)
**WARNING:** Using the wrong method or accidentally using the wrong pinout might
permanently damage your hardware!
**WARNING:** Do not rely on dots *painted* on flash ICs to orient the pins!
Any dots painted on flash ICs may only indicate if they've been tested. Dots
that appear in datasheets to indicate pin 1 correspond to some kind of physical
marker, such as a drilled hole, or one side being more flat than the other.
## Using a layout file
On platforms where the flash IC is shared with other components you might want
to write only a part of the flash IC. On Intel for example there are IFD, ME and
GBE which don't need to be updated to install coreboot.
To make [flashrom] only write the *bios* region, leaving Intel ME and Intel IFD
untouched, you can use a layout file, which can be created with ifdtool and a backup
of the original firmware.
```bash
ifdtool -f rom.layout backup.rom
```
and looks similar to:
```
00000000:00000fff fd
00500000:00bfffff bios
00003000:004fffff me
00001000:00002fff gbe
```
By specifying *-l* and *-i* [flashrom] writes a single region:
```bash
flashrom -l rom.layout -i bios -w coreboot.rom -p <programmer>
```
## Using an IFD to determine the layout
flashrom version 1.0 supports reading the layout from the IFD (first 4KiB of
the ROM). You don't need to manually specify a layout it, but it only works
under the following conditions:
* Only available on Intel ICH7+
* There's only one flash IC when flashing externally
```bash
flashrom --ifd -i bios -w coreboot.rom -p <programmer>
```
**TODO** explain FMAP regions, normal/fallback mechanism, flash lock mechanisms
[flashrom]: https://www.flashrom.org/Flashrom
|
