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author | Patrick Rudolph <siro@das-labor.org> | 2018-08-04 10:04:45 +0200 |
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committer | Philipp Deppenwiese <zaolin.daisuki@gmail.com> | 2018-09-30 03:20:36 +0000 |
commit | 15d840558480536ddaca71bc1876254d59fca7fe (patch) | |
tree | ecbb8b330e53b9413eaf17a72e0fb79a9ed2523f /Documentation/flash_tutorial/ext_power.md | |
parent | 3d1d966dd8866e8fd399f988b38b7ceba9f4cfee (diff) | |
download | coreboot-15d840558480536ddaca71bc1876254d59fca7fe.tar.xz |
Documentation: Add basic flashing tutorial for Lenovo
* Add basic flashing tutorial
** Describe internal and external flashing
** Describe flash supply diode protection
** Gives general advices on flashing
** Describe how to use flashrom --ifd
* Describe basic flashing on Lenovo T4xx devices
** Describe how to disassemble and access the flash IC on T4xx
** Describe flash layout on Sandy Bridge and Ivy Bridge series.
Change-Id: Ia833e27f4e7d89ee32be9bed21a0c021839facec
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/27852
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Diffstat (limited to 'Documentation/flash_tutorial/ext_power.md')
-rw-r--r-- | Documentation/flash_tutorial/ext_power.md | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/Documentation/flash_tutorial/ext_power.md b/Documentation/flash_tutorial/ext_power.md new file mode 100644 index 0000000000..542ccfd934 --- /dev/null +++ b/Documentation/flash_tutorial/ext_power.md @@ -0,0 +1,28 @@ +# Flashing firmware externally supplying direct power + +**WARNING:** Never use a high current rated power supply, like PC ATX power + supply. It'll literally melt your PCB traces on short circuit. + +On some mainboards the flash IC Vcc pin is connected to a diode, which prevents +powering the rest of the board. + +![][flash_ic_diode] + +Please have a look at the mainboard specific documentation for details. + +On those boards it's safe to use a programmer and supply power externally. + +**WARNING:** Verify that you apply the correct voltage! + +## USB programmer +USB programmers are usually current limited by the host USB hub. On USB 2.0 +ports the limit is 500mA, which is sufficient to power the flash. Those are +the best choice as they are stateless and have a fast power on reset cycle. + +## Single board computers (like BeagleBone Black / RPi) +Be careful when connecting a flash chip, especially when using a Pomona +test-clip. A short circuit or overcurrent (250mA) causes a brown-out reset, +resulting in a reboot of the running operating system (and possible loss of +remote shell). + +[flash_ic_diode]: flash_ic_diode.svg |