Re: Using serial port on RPi

[John Klos <john%ziaspace.com@localhost>]

> > I'd like to use the primary serial port on a Raspberry Pi 3. However, I
> > haven't quite figured out how to tell the kernel to not use the serial
> > port to mirror the graphics console.
>
> Use a kernel without option WSDISPLAY_MULTICONS.

That's great!

Interestingly, I still get a segment of the kernel's boot messages on the 
serial port:

[   1.0000030] com0 at simplebus1: BCM AUX UART, 1-byte FIFO
[   1.0000030] com0: console
[   1.0000030] com0: interrupting on icu irq 29
[   1.0000030] mmcpwrseq0 at simplebus0: couldn't get reset GPIOs
[   1.0000030] /soc/thermal@7e212000 at simplebus1 not configured
[   1.0000030] bcmdmac0 at simplebus1: DMA0 DMA2 DMA4 DMA5 DMA8 DMA9 DMA10 DMA11
[   1.0000030] /soc/power at simplebus1 not configured
[   1.0000030] /phy at simplebus0 not configured
[   1.0000030] bsciic0 at simplebus1: Broadcom Serial Controller
[   1.0000030] bsciic0: interrupting on icu irq 53
[   1.0000030] iic0 at bsciic0: I2C bus
[   1.0000030] bcmmbox0 at simplebus1: VC mailbox
[   1.0000030] bcmmbox0: interrupting on icu irq 65
[   1.0000030] vcmbox0 at bcmmbox0
[   1.0000030] /soc/timer@7e003000 at simplebus1 not configured
[   1.0000030] /soc/txp@7e004000 at simplebus1 not configured
[   1.0000030] bcmsdhost0 at simplebus1: SD HOST controller
[   1.0000030] bcmsdhost0: interrupting on icu irq 56
[   1.0000030] bsciic1 at simplebus1: Broadcom Serial Controller
[   1.0000030] bsciic1: interrupting on icu irq 53
[   1.0000030] iic1 at bsciic1: I2C bus
[   1.0000030] /soc/pwm@7e20c000 at simplebus1 not configured
[   1.0000030] sdhc0 at simplebus1: SDHC controller
[   1.0000030] sdhc0: interrupting on icu irq 62
[   1.0000030] bsciic2 at simplebus1: Broadcom Serial Controller
[   1.0000030] bsciic2: interrupting on icu irq 53
[   1.0000030] iic2 at bsciic2: I2C bus
[   1.0000030] dwctwo0 at simplebus1: USB controller
[   1.0000030] dwctwo0: interrupting on icu irq 9
[   1.0000030] bcmpmwdog0 at simplebus1: Power management, Reset and Watchdog controller
[   1.0000030] /soc/vec@7e806000 at simplebus1 not configured
[   1.0000030] /soc/hdmi@7e902000 at simplebus1 not configured
[   1.0000030] /soc/gpu at simplebus1 not configured
[   1.0000030] genfb0 at simplebus1: switching to framebuffer console

I suppose this is fine as long as I delay the booting of the machine to 
which it'll be connected so this output doesn't stop the booting of that 
machine.

It points out another issue: removing WSDISPLAY_MULTICONS means the system 
can be halted without the inevitable USB panic about half the time. With 
WSDISPLAY_MULTICONS, every halt leads to a panic if any USB device is 
plugged in:

[  45.1604394] syncing disks... done
[  45.1804451] unmounting file systems...
[  45.4805224] unmounting done
[  45.4905286] The operating system has halted.
[  45.5005297] Please press any key to reboot.
[  46.4607325] Skipping crash dump on recursive panic
[  46.4607325] panic: usbd_transfer: not done
[  46.4707344] cpu1: Begin traceback...
[  46.4707344] trace fp ffffc0007f053b30
[  46.4807367] fp ffffc0007f053b60 vpanic() at ffffc0000057e5d8 netbsd:vpanic+0x178
[  46.4907394] fp ffffc0007f053bc0 panic() at ffffc0000057e6e4 netbsd:panic+0x44
[  46.5107457] fp ffffc0007f053c50 usbd_transfer() at ffffc000001791f4 netbsd:usbd_transfer+0x504
[  46.5207462] fp ffffc0007f053c90 usbd_do_request_len() at ffffc0000017a8d8 netbsd:usbd_do_request_len+0xf8
[  46.5507553] fp ffffc0007f053d00 smsc_readreg.part.0() at ffffc000001ca1ec netbsd:smsc_readreg.part.0+0x3c
[  46.5707601] fp ffffc0007f053d40 smsc_wait_for_bits() at ffffc000001ca2c4 netbsd:smsc_wait_for_bits+0x74
[  46.5907679] fp ffffc0007f053d80 smsc_uno_miibus_readreg() at ffffc000001ca824 netbsd:smsc_uno_miibus_readreg+0x50
[  46.6207747] fp ffffc0007f053dc0 smscphy_service() at ffffc0000038b884 netbsd:smscphy_service+0xe4
[  46.6407795] fp ffffc0007f053e00 mii_tick() at ffffc0000037cb14 netbsd:mii_tick+0x54
[  46.6707911] fp ffffc0007f053e20 usbnet_tick_task() at ffffc00000180f48 netbsd:usbnet_tick_task+0xa8
[  46.6907952] fp ffffc0007f053e70 usb_task_thread() at ffffc00000176c34 netbsd:usb_task_thread+0xd4
[  46.7208066] tf ffffc0007f053ed0 el0_trap() at ffffc000000b57f0 netbsd:el1_trap_exit+0x68
[  46.7408098] cpu1: End traceback...

Thanks! I learned something new today :)

John