From 15d840558480536ddaca71bc1876254d59fca7fe Mon Sep 17 00:00:00 2001 From: Patrick Rudolph Date: Sat, 4 Aug 2018 10:04:45 +0200 Subject: 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 Reviewed-on: https://review.coreboot.org/27852 Tested-by: build bot (Jenkins) Reviewed-by: Philipp Deppenwiese --- Documentation/flash_tutorial/no_ext_power.md | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 Documentation/flash_tutorial/no_ext_power.md (limited to 'Documentation/flash_tutorial/no_ext_power.md') diff --git a/Documentation/flash_tutorial/no_ext_power.md b/Documentation/flash_tutorial/no_ext_power.md new file mode 100644 index 0000000000..b97ba4cc7a --- /dev/null +++ b/Documentation/flash_tutorial/no_ext_power.md @@ -0,0 +1,22 @@ +# Flashing firmware externally supplying no power + +On some mainboards the flash IC's Vcc pin is connected to the internal +power-rail, powering the entire board if the flash IC is powered externally. +Likely it powers other chips which access the flash IC, preventing the external +programmer from reading/writing the chip. It also violates the components' +power sequence, bringing the ICs into an undefined state. + +![][flash_ic_no_diode] + +Please have a look at the mainboard specific documentation for details. + +On those boards it's recommended to use a programmer without supplying power +externally. + +The key to read and write the flash IC is to put the machine into *S3* sleep- +state or *S5* sleep-state *maybe* with Wake-On-LAN enabled. +Another option that sometimes works is to keep the device in reset. This method requires +knowledge of the board schematics and might require hardware modifications. +Use a multimeter to make sure the flash IC is powered in those sleep states. + +[flash_ic_no_diode]: flash_ic_no_diode.svg -- cgit v1.2.3