mb/hp: Add EliteBook 820 G2

Most of the components of this laptop are tested to work,
which is listed in the documentation.

Change-Id: Id8b3b7f735460c5e76a2dc9ab2d10154e6606ad6
Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46630
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

Documentation/mainboard/hp/elitebook_820_g2.md

@@ -0,0 +1,141 @@
+# HP EliteBook 820 G2
+
+This page is about the notebook [HP EliteBook 820 G2].
+
+## Release status
+
+HP EliteBook 820 G2 was released in 2015 and is now end of life.
+It can be bought from a secondhand market like Taobao or eBay.
+
+## Required proprietary blobs
+
+The following blobs are required to operate the hardware:
+
+1. EC firmware
+2. Intel ME firmware
+3. Broadwell mrc.bin and refcode.elf
+
+HP EliteBook 820 G2 uses SMSC MEC1324 as its embedded controller.
+The EC firmware is stored in the flash chip, but we don't need to touch it
+or use it in the coreboot build process.
+
+Intel ME firmware is in the flash chip. It is not needed when building coreboot.
+
+The Broadwell memory reference code binary and reference code blob is needed
+when building coreboot. Read the document [Blobs used in Intel Broadwell boards]
+on how to get these blobs.
+
+## Programming
+
+Before flashing, remove the battery and the hard drive cover according to the
+[Maintenance and Service Guide] of this laptop.
+
+HP EliteBook 820 G2 has two flash chips, a 16MiB system flash, and a 2MiB
+private flash. To install coreboot, we need to program both flash chips.
+Read [HP Sure Start] for detailed information.
+
+![HP EliteBook 820 G2 flash chip](elitebook_820_g2_flash.jpg)
+
+To access the system flash, we need to connect the AC adapter to the machine,
+then clip on the flash chip with an SOIC-8 clip. An [STM32-based flash programmer]
+made with an STM32 development board is tested to work.
+
+To access the private flash chip, we can use a ch341a based flash programmer and
+flash the chip with the AC adapter disconnected.
+
+To flash coreboot on a board running OME firmware, create a backup for both flash
+chips, then do the following:
+
+1. Erase the private flash to disable the IFD protection
+2. Modify the IFD to shrink the BIOS region, so that we can put the firmware outside
+   the protected flash region
+
+To erase the private flash chip, attach it with the flash programmer via the SOIC-8 clip,
+then run:
+
+    flashrom -p <programmer> --erase
+
+To modify the IFD, write the following flash layout to a file:
+
+    00000000:00000fff fd
+    00001000:00002fff gbe
+    00003000:005fffff me
+    00600000:00bfffff bios
+    00eb5000:00ffffff pd
+
+Suppose the above layout file is ``layout.txt`` and the origin content of the system flash
+is in ``factory-sys.rom``, run:
+
+    ifdtool -n layout.txt factory-sys.rom
+
+Then a flash image with a new IFD will be in ``factory-sys.rom.new``.
+
+Flash the IFD of the system flash:
+
+    flashrom -p <programmer> --ifd -i fd -w factory-sys.rom.new
+
+Then flash the coreboot image:
+
+    # first extend the 12M coreboot.rom to 16M
+    fallocate -l 16M build/coreboot.rom
+    flashrom -p <programmer> --ifd -i bios -w build/coreboot.rom
+
+After coreboot is installed, the coreboot firmware can be updated with internal flashing:
+
+    flashrom -p internal --ifd -i bios --noverify-all -w build/coreboot.rom
+
+## Debugging
+
+The board can be debugged with EHCI debug. The EHCI debug port is the USB port on the left.
+
+## Test status
+
+### Untested
+
+- NFC module
+- Fingerprint reader
+- Smart Card reader
+
+### Working
+
+- mainboards with i3-5010U, i5-5300U CPU, 16G+8G DDR3L memory
+- SATA and M.2 SATA disk
+- PCIe SSD
+- Webcam
+- Touch screen
+- Audio output from speaker and headphone jack
+- Intel GbE (needs a modified refcode documented in [Blobs used in Intel Broadwell boards])
+- WLAN
+- WWAN
+- SD card reader
+- Internal LCD, DisplayPort and VGA video outputs
+- Dock
+- USB
+- Keyboard and touchpad
+- EC ACPI
+- S3 resume
+- TPM
+- Arch Linux with Linux 5.11.16
+- Broadwell MRC version 2.6.0 Build 0 and refcode from Purism Librem 13 v1
+- Graphics initialization with libgfxinit
+- Payload: SeaBIOS 1.16.2
+- EC firmware: KBC Revision 96.54 from OEM firmware version 01.05
+- Internal flashing under coreboot
+
+## Technology
+
+```eval_rst
++------------------+-----------------------------+
+| SoC              | Intel Broadwell             |
++------------------+-----------------------------+
+| EC               | SMSC MEC1324                |
++------------------+-----------------------------+
+| Coprocessor      | Intel Management Engine     |
++------------------+-----------------------------+
+```
+
+[HP EliteBook 820 G2]: https://support.hp.com/us-en/product/HP-EliteBook-820-G2-Notebook-PC/7343192/
+[Blobs used in Intel Broadwell boards]: ../../soc/intel/broadwell/blobs.md
+[Maintenance and Service Guide]: http://h10032.www1.hp.com/ctg/Manual/c04775894.pdf
+[STM32-based flash programmer]: https://github.com/dword1511/stm32-vserprog
+[HP Sure Start]: hp_sure_start.md

Documentation/mainboard/index.md

@@ -85,6 +85,7 @@ The boards in this section are not real mainboards, but emulators.
 - [EliteBook 2560p](hp/2560p.md)
 - [EliteBook 8760w](hp/8760w.md)
 - [EliteBook Folio 9480m](hp/folio_9480m.md)
+- [EliteBook 820 G2](hp/elitebook_820_g2.md)
 
 ## Intel