Add installation instructions for Raspberry Pi 4, covering what hardware

you will currently need to run OpenBSD on the board, steps to take, and
what you should expect to see.  ok kettenis@

1 files changed, 32 insertions, 3 deletions

diff --git a/distrib/notes/arm64/prep b/distrib/notes/arm64/prep
index 5ffd54879aa..e74ad22f3a6 100644
--- a/distrib/notes/arm64/prep
+++ b/distrib/notes/arm64/prep
@@ -1,4 +1,4 @@
-dnl	$OpenBSD: prep,v 1.9 2020/04/15 11:41:08 kettenis Exp $
+dnl	$OpenBSD: prep,v 1.10 2020/04/19 23:41:19 sthen Exp $
 Please be aware that OpenBSD support for this platform is far from
 complete.
 
@@ -24,11 +24,11 @@ Booting from an SD card:
   storage devices.  Under OpenBSD, it will appear as a ``sd'' device, for
   example sd1.
   
-  Use the dd(1) utility to copy the miniroot to the hard drive.
+  Use the dd(1) utility to copy the miniroot to the SD card.
   The command would likely be, under OpenBSD:
   	dd if=miniroot{:--:}OSrev.fs of=/dev/rsd1c bs=1m
   
-  When you have connected the serial to you computer, a command such
+  When you have connected the serial to your computer, a command such
   as "cu -l cuaU0 -s 115200" (assuming cuaU0 is your serial port device)
   should connect you to the board's console.
 
@@ -49,6 +49,35 @@ script.
 The bootloader will then run and try to load sd0a:/bsd off an FFS
 filesystem after a timeout.
 
+Install on Raspberry Pi 4:
+
+  You will need a microSD card (only a small one is needed), a USB
+  storage device, a TTL serial interface adapter (e.g. CP2102 USB-UART
+  converter), and a cable to attach this to the TXD/RXD/GND pins on the
+  https://pinout.xyz/ header on the board.
+
+  Follow the installation instructions at https://github.com/pftf/RPi4
+  to install UEFI firmware to a FAT-formatted microSD card.
+
+  Use the dd(1) utility to copy the miniroot to the USB storage device.
+  The command would likely be, under OpenBSD:
+	dd if=miniroot{:--:}OSrev.fs of=/dev/rsd1c bs=1m
+
+  When you have connected the serial to your computer, a command such
+  as "cu -l cuaU0 -s 115200" (assuming cuaU0 is your serial port device)
+  should connect you to the board's console.
+
+  Shortly after powering the board, you should see messages on the serial
+  console starting with "Initialising SDRAM" followed by messages from the
+  UEFI firmware.  If you have a monitor connected to the HDMI port, you
+  should see a multi-coloured screen followed by UEFI firmware output.
+  If you do not see this, re-check your UEFI firmware installation.
+
+  OpenBSD should boot automatically soon after loading the UEFI firmware.
+  If a monitor is connected you will see messages from the boot loader,
+  but after the kernel has started running you will only see output on
+  the serial console.
+
 Install on systems without a supported miniroot:
 
   If a miniroot is not available for your system you will have to modify