1Using PCI serial ports for debugging 2==================================== 3 4Modern systems usually don't come with a built-in serial port anymore. This 5is unconvenient for low level debugging, since the serial port allows access 6to early boot log as well as kernel debugger, even when the display or keyboard 7are not working. 8 9It is fortunately possible to add a serial port over the PCI bus on machines 10which have appropriate expansion ports. This can be done using expresscard, 11mini-PCI, or PCI express ports. 12 13Devices known to work 14--------------------- 15 16Dexlan XMT01A (https://www.accessoires-informatiques.com/Prix/EXPRESSCARD-PCIE-POUR-PORTABLE-23842.html) 17 Uses MOSCHIP 9922 controller 18 19Devices to be tested 20-------------------- 21 22https://smile.amazon.com/Industrial-Desktop-Bracket-Moschip-MCS9922/dp/B003D3MFHM/ 23 24Configuring 25----------- 26 27- Install the card in your computer 28- Boot Haiku and look in the syslog for the PCI bus scan for the device: 29 30.. code-block:: text 31 32 KERN: PCI: [dom 0, bus 5] bus 5, device 0, function 0: vendor 9710, device 9922, revision 00 33 KERN: PCI: class_base 07, class_function 00, class_api 02 34 KERN: PCI: vendor 9710: MosChip Semiconductor Technology Ltd. 35 KERN: PCI: device 9922: MCS9922 PCIe Multi-I/O Controller 36 KERN: PCI: info: Communication controller (Serial controller, 16550) 37 KERN: PCI: line_size 10, latency 00, header_type 80, BIST 00 38 KERN: PCI: ROM base host 00000000, pci 00000000, size 00000000 39 KERN: PCI: cardbus_CIS 00000000, subsystem_id 1000, subsystem_vendor_id a000 40 KERN: PCI: interrupt_line 0b, interrupt_pin 01, min_grant 00, max_latency 00 41 KERN: PCI: base reg 0: host 00004000, pci 0000KERN: 4000, size 00000008, flags 01 42 KERN: PCI: base reg 1: host f1c01000, pci f1c01000, size 00001000, flags 00 43 KERN: PCI: base reg 2: host 00000000, pci 00000000, size 00000000, flags 00 44 KERN: PCI: base reg 3: host 00000000, pci 00000000, size 00000000, flags 00 45 KERN: PCI: base reg 4: host 00000000, pci 00000000, size 00000000, flags 00 46 KERN: PCI: base reg 5: host f1c00000, pci f1c00000, size 00001000, flags 00 47 KERN: PCI: Capabilities: MSI, PM, PCIe 48 KERN: PCI: Extended capabilities: Virtual Channel, Advanced Error Reporting 49 50 51Write down the address of "base reg 0", this is where the serial port registers 52are mapped (it is probably possible to get this information from lspci on Linux 53as well?) 54 55Configure serial debug in config/settings/kernel/drivers/kernel: 56 57.. code-block:: text 58 59 serial_debug_output true 60 serial_debug_speed 115200 61 serial_debug_port 0x4000 62 63Now your kernel is configured to send its output to the serial port. You can 64connect another machine to it (using an USB to serial adapter and a NULL modem 65cable, for example) and use SerialConnect or a similar tool to see the output 66and access the KDL prompt. 67 68Happy debugging! 69