ref: 887ae1a17b54babf6a0946872bf6faaac1427be1
dir: /sys/src/9/bcm/words/
raspberry pi
broadcom 2835 SoC (based on 2708)
arm1176jzf-s (v6 arch) 700MHz cpu, apparently dual-issue, with vfp2
videocore 4 gpu
l1 I & D VIPT caches
16K each: 4-way, 128 sets, 32-byte lines
l1 D is write-through, l1 I is write-back
unified l2 PIPT cache 128K: 4-way?, 1024? sets, 32-byte lines, mostly for gpu
(by default CPU doesn't see it)
we arrange that device register accesses are uncached.
256MB of dram at physical address 0, shared with gpu
non-16550 uart for console
uart serial voltages are wrong (3.3v but rs232 is nominally 12v);
could use usb serial (ick).
there's no real ethernet controller, so we have to use usb ether,
and the usb controller is nastier than usual.
There's a serial port (115200b/s) on P1 connector pins (GND,TXD,RXD) =
(6,8,10). These are 3v TTL signals: use a level-shifter to convert to
RS232, or a USB-to-TTL-serial adapter. Add the line "console=0
b115200" to the /cfg/pxe file on the server, or the parameter
"console='0 b115200'" to cmdline.txt on the SD card.
9pi is a Plan 9 terminal, which can boot with local fossil root on the
sd card (/dev/sdM0), or with root from a Plan 9 file server via tcp.
9picpu is a Plan 9 cpu server, which could be used in a headless
configuration without screen, keyboard or mouse.
9pifat is a minimal configuration which boots a shell script boot.rc
with root in /plan9 on the dos partition, maybe useful for embedded
applications where a full Plan 9 system is not needed.
Network booting with u-boot:
start with a normal rpi u-boot sd (e.g. raspberry-pi-uboot-20120707).
update the start.elf with a version from a newer rpi distro (see below).
mk installall
add new system to ndb
see booting(8)
Booting from sd card:
- start with a normal rpi distro sd (e.g. 2012-08-16-wheezy-raspbian)
[NB: versions of start.elf earlier than this may not be compatible]
- copy 9pi to sd's root directory
- add or change "kernel=" line in config.txt to "kernel=9pi"
- plan9.ini is built from the "kernel arguments" in cmdline.txt - each
var=value entry becomes one plan9.ini line, so entries with spaces will
need single quotes.
physical mem map
hex addr size what
----
0 256MB sdram, cached
00000000 64 exception vectors
00000100 7936 boot ATAGs (inc. cmdline.txt)
00002000 4K Mach
00003000 1K L2 page table for exception vectors
00003400 1K videocore mailbox buffer
00003800 2K FIQ stack
00004000 16K L1 page table for kernel
00008000 - default kernel load address
01000000 16K u-boot env
20000000 16M peripherals
20003000 system timer(s)
20007000 dma
2000B000 arm control: intr, timers 0 & 1, semas, doorbells, mboxes
20100000 power, reset, watchdog
20200000 gpio
20201000 uart0
20202000 mmc
20215040 uart1 (mini uart)
20300000 eMMC
20600000 smi
20980000 otg usb
40000000 l2 cache only
7e00b000 arm control
7e2000c0 jtag
7e201000? pl011 usrt
7e215000 aux: uart1, spi[12]
80000000
c0000000 bypass caches
virtual mem map (from cpu address map & mmu mappings)
hex addr size what
----
0 512MB user process address space
7e000000 16M i/o registers
80000000 <=224M kernel ram (reserve some for GPU)
c0000000 256MB kzero, mapped to 0
ffff0000 4K exception vectors
Linux params at *R2 (default 0x100) are a sequence of ATAGs
struct atag {
u32int size; /* size of ATAG in words, including header */
u32int tag; /* ATAG_CORE is first, ATAG_NONE is last */
u32int data[size-2];
};
00000000 ATAG_NONE
54410001 ATAG_CORE
54410002 ATAG_MEM
54410009 ATAG_CMDLINE
uart dmas 15, 14
intrs (96)
irq1
0 timer0
1 timer1
2 timer2
3 timer3
8 isp
9 usb
16 dma0
17 dma1
⋯
28 dma12
29 aux: uart1
30 arm
31 vpu dma
irq2
35 sdc
36 dsio
40 hdmi0
41 hdmi1
48 smi
56 sdio
57 uart1 aka "vc uart"
irq0
64 timer
65 mbox
66 doorbell0
67 doorbell1
75 usb
77 dma2
78 dma3
82 sdio
83 uart0