ref: f6b4d9b9dc53c2842b23dee80081cb5a874a1138
parent: 4be504ebed25aee25578d461e5b7ac3779fbb049
author: mkf <mkf@cloud9p.org>
date: Sat Aug 10 15:47:24 EDT 2024
some notes on pi
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+.HTML "plan 9 on pi"
+.TL
+template
+
+.AU
+mkf
+
+.AB
+Tips for running plan 9 on raspberry pi
+
+.AE
+
+.LP
+Raspberry pi is a single board computer made raspberry pi people
+somewhere in uk, in 2012(?) richard miller ported plan 9 port.
+this is known as miller's pi. at some point 9front have imported miller's code.
+9front have since got a 64-bit version of bcm kernel.
+this guide covers 9front, more info on miller's is appercited.
+.NH
+installtion
+.LP
+As time of writing by default 9front ships with hjfs on installation image and that image is sized 2Gb.
+You can dd (or cp, or whatever your prefered method may be) that into your sdcard.
+That's all.
+.NH .1
+Resizing the paritions
+.LP
+Hjfs however does not support growing a parition (gefs seems to be the only file system capable of doing so),
+Thus to do so. you may need to do a classic installation, there are many ways for it;
+but the easiest way is to install using a usb thumb drive.
+.IP \(bu
+copy 9front image into your sdcard, we need to do this since we need to have the kernel and boot blobs
+.IP \(bu
+then copy same thing into your sdcard, for file system contents
+.IP \(bu
+boot the pi, select the usb in bootargs
+.IP \(bu
+run inst/start, make the partitions as you would on the sdcard, and install.
+.NH
+ISSUES
+.NH .1
+audio
+.LP
+Pi is odd, audio hardware in pi is perhaps the most odd part of it.
+Use usb audio cards if you can, but if you can't:
+.IP 1.
+3.5mm audio uses a PWM connected to arm core, and offers poor quality:
+but is much simpler. load on cpu sometimes casues noticable effects on PWM,
+and thus audiable and annoying noise.
+.IP 2.
+HDMI audio is much more sophisticated (or horribly complex, depending on your point of view),
+and uses a RPC protocol to communicate with broadcom core. offers better audio.
+.LP
+There are two drivers for PWM, one is located under
+CW /n/extra/src/audiobcm.tgz
+and said to be working for first pi (bcm2385).
+I haven't tested it, but PWM audio interface have been realtively same since
+bcm2385 (with some minor improvments) from arm core's view point.