# HP ProBook 6550b, serial port uart0 missing



## Juha Nurmela (Nov 20, 2015)

The laptop has one serial port, but it shows up nowhere. Nothing special visible with `boot -v` and nothing by *inb*:ing from 0x3F8...F, just 0xFF. BIOS settings checked (I think) thoroughly. I've read about `acpidump` but that path frightens me.

Anyone know if it's worthwhile to study the _ASL_, _DSDT_ etc, or to get a copy of Windows and hope for a non-volatile setting therein.

Juha

Ugly solution in laptop compat thread https://forums.freebsd.org/threads/17308/page-5#post-304594


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## tingo (Nov 20, 2015)

No unknown devices in `# pciconf -l` output?


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## wblock@ (Nov 20, 2015)

It would not appear as a device or sysctl called uart0 on FreeBSD, it would be /dev/cuau0.

Is the port enabled in the BIOS?  What does `sysctl dev.uart` show?


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## Juha Nurmela (Nov 20, 2015)

```
FreeBSD 10.1-RELEASE-p10 #0: ...  i386
```
Something that should have been said in the first post.

```
none0@pci0:0:22:0:  class=0x078000 card=0x146d103c chip=0x3b648086 rev=0x06 hdr=0x00
  vendor  = 'Intel Corporation'
  device  = '5 Series/3400 Series Chipset HECI Controller'
  class  = simple comms
  bar  [10] = type Memory, range 64, base 0xd4824000, size 16, enabled
isab0@pci0:0:31:0:  class=0x060100 card=0x146d103c chip=0x3b0b8086 rev=0x05 hdr=0x00
  vendor  = 'Intel Corporation'
  device  = 'Mobile 5 Series Chipset LPC Interface Controller'
  class  = bridge
  subclass  = PCI-ISA
```
I don't know what the first one is, but googling HECI didn't look promising. Second one, LPC, contains the serial port, I think. Paralllel port *does* show up. There's no physical LPT connector though without a dock 


```
hopo # sysctl -a |grep uart
device  uart_ns8250
device  uart
```

Ah... I have *not* yet tried to use the driver as a module.

All BIOS settings that even remotely look like affecting serial ports have been tried.
It is possible that I missed one permutation, though.

I think (in a rut?)  there's some non-standard knob in the *DSDT*, which must be enabled for the uart to function.
`acpidump` `asl` and company just look so ugly, that I prefer a nicely working laptop without uart to a brick. I should have looked around in the pre-installed Windows first, instead of immediately overwriting it.

There is also a module `acpi_hp` and device /dev/hpcmi which might be related. Reading hpcmi takes about 5 seconds, 5 seconds busy in the read system call, and result is 169 newlines and nothing else.

Thanks,
Juha


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