1.. SPDX-License-Identifier: GPL-2.0+ 2.. Copyright 2020 Google LLC 3 4Chromium OS Support in U-Boot 5============================= 6 7Introduction 8------------ 9 10This describes how to use U-Boot with Chromium OS. Several options are 11available: 12 13 - Running U-Boot from the 'altfw' feature, which is available on selected 14 Chromebooks from 2019 onwards (initially Grunt). Press '1' from the 15 developer-mode screen to get into U-Boot. See here for details: 16 https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_mode.md 17 18 - Running U-Boot from the disk partition. This involves signing U-Boot and 19 placing it on the disk, for booting as a 'kernel'. See 20 :doc:`chainload` for information on this. This is the only 21 option on non-U-Boot Chromebooks from 2013 to 2018 and is somewhat 22 more involved. 23 24 - Running U-Boot with Chromium OS verified boot. This allows U-Boot to be 25 used instead of either or both of depthcharge (a bootloader which forked 26 from U-Boot in 2013) and coreboot. See :doc:`run_vboot` for more 27 information on this. 28 29 - Running U-Boot from coreboot. This allows U-Boot to run on more devices 30 since many of them only support coreboot as the bootloader and have 31 no bare-metal support in U-Boot. For this, use the 'coreboot' target. 32 33 - Running U-Boot and booting into a Chrome OS image, but without verified 34 boot. This can be useful for testing. 35 36 37Talks and documents 38------------------- 39 40Here is some material relevant to Chromium OS verified boot with U-Boot: 41 42 - "U-Boot with Chrome OS and firmware packaging" 43 44 - Author: Simon Glass 45 - Presented at Open Source Firmware Conference 2018, Erlangen 46 - Describes the work in progress as at the end of 2018 47 - Slides at `OSFC <https://2018.osfc.io/uploads/talk/paper/26/U-Boot_with_Chrome_OS_and_firmware_packaging.pdf>`_ 48 - `Youtube video 'OSFC - U-Boot with Chrome OS and firmware packaging' <https://www.youtube.com/watch?v=1jknxUvmwpo>`_ 49 50 - "Verified Boot in Chrome OS and how to make it work for you" 51 52 - Author: Simon Glass 53 - Presented at ELCE 2013, Edinburgh 54 - Describes the original 2013 implementation as shipped on snow (first 55 `ARM Chromebook was a Samsung Chromebook <https://www.cnet.com/products/samsung-series-3-chromebook-xe303c12-11-6-exynos-5250-2-gb-ram-16-gb-ssd-bilingual-english-french/>`_ 56 with Samsung Exynos5250 `review <https://www.cnet.com/reviews/samsung-chromebook-series-3-review/>`_), 57 spring (`HP Chromebook 11 <https://www.cnet.com/products/hp-chromebook-11-g2-11-6-exynos-5250-4-gb-ram-16-gb-emmc/>`_) 58 and pit/pi (`Samsung Chromebook 2 <https://www.cnet.com/products/samsung-chromebook-2-xe503c12-11-6-exynos-5-octa-4-gb-ram-16-gb-ssd/>`_ 59 with Exynos 5 Octa 5420 in 2014). 60 - Slides at `Google research <https://research.google/pubs/pub42038/>`_ 61 - `Youtube video 'Verified Boot on Chrome OS and How to do it yourself' <https://www.youtube.com/watch?v=kdpZC9jFzZA>`_ 62 63 - "Chrome University 2018: Chrome OS Firmware and Verified Boot 201" 64 65 - Author: Duncan Laurie 66 - Describes Chrome OS firmware as of 2018 and includes a wide range of 67 topics. This has no U-Boot information, but does cover coreboot and also 68 talks about the Chrome OS EC and Security chip. This is probably the 69 best introduction talk. 70 - `Youtube video 'Chrome University 2018: Chrome OS Firmware and Verified Boot 201' <https://www.youtube.com/watch?v=WY2sWpuda2g>`_ 71 72 - `Chromium OS U-Boot <https://www.chromium.org/developers/u-boot>`_ 73 74 - `Firmware porting Guide <https://www.chromium.org/chromium-os/firmware-porting-guide>`_ 75