Документация EXAR была правильной. Эта плата будет поддерживается современными ядрами Linux. Эта проблема для меня заключалась в том, что мое ядро было настроено на поддержку только 4 последовательных портов, всего.
На Hummingboard встроенные UART использовали первые 4 UART. Я перенастроил ядро на 16 последовательных портов, макс. Восстановил мое ядро, следуя методу, специфичному для Debian . Rebooted.
root@torpedo:~# uname -a Linux torpedo 4.16.2whoi-armhf #1 SMP Wed Apr 18 16:56:21 GMT 2018 armv7l GNU/Linux
Новое ядро установлено и работает ... проверьте шину PCI:
root@torpedo:~# lspci -vv ... 01:00.0 Serial controller: Exar Corp. Device 0354 (rev 03) (prog-if 02 [16550]) Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping- SERR+ FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- Latency: 0, Cache Line Size: 64 bytes Interrupt: pin A routed to IRQ 334 Region 0: Memory at 01100000 (32-bit, non-prefetchable) [size=16K] Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+ Address: 0000000000000000 Data: 0000 Capabilities: [78] Power Management version 3 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold-) Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME- Capabilities: [80] Express (v2) Endpoint, MSI 01 DevCap: MaxPayload 256 bytes, PhantFunc 0, Latency L0s <64ns, L1 <1us ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset- DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported- RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ MaxPayload 128 bytes, MaxReadReq 512 bytes DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend- LnkCap: Port #1, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit Latency L0s <64ns, L1 <1us ClockPM- Surprise- LLActRep- BwNot- LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk- ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt- LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt- DevCap2: Completion Timeout: Not Supported, TimeoutDis-, LTR-, OBFF Not Supported DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis- Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS- Compliance De-emphasis: -6dB LnkSta2: Current De-emphasis Level: -3.5dB, EqualizationComplete-, EqualizationPhase1- EqualizationPhase2-, EqualizationPhase3-, LinkEqualizationRequest- Capabilities: [100 v1] Virtual Channel Caps: LPEVC=0 RefClk=100ns PATEntryBits=1 Arb: Fixed- WRR32- WRR64- WRR128- Ctrl: ArbSelect=Fixed Status: InProgress- VC0: Caps: PATOffset=00 MaxTimeSlots=1 RejSnoopTrans- Arb: Fixed- WRR32- WRR64- WRR128- TWRR128- WRR256- Ctrl: Enable+ ID=0 ArbSelect=Fixed TC/VC=ff Status: NegoPending- InProgress- Kernel driver in use: exar_serial
Похоже, я не сломал шину PCI.
Ядро нашло UART?
root@torpedo:~# dmesg|grep tty [ 0.000000] Kernel command line: root=/dev/mmcblk0p1 rootfstype=ext4 rootwait console=tty1 consoleblank=0 video=mxcfb0:dev=hdmi,1920x1080m60,if=RGB24,bpp=32 rd.dm=0 rd.luks=0 rd.lvm=0 raid=noautodetect pci=nomsi vt.global_cursor_default=0 loglevel=1 [ 0.001375] console [tty1] enabled [ 1.220660] 0000:01:00.0: ttyS0 at MMIO 0x1100000 (irq = 334, base_baud = 7812500) is a XR17V35X [ 1.221093] 0000:01:00.0: ttyS1 at MMIO 0x1100400 (irq = 334, base_baud = 7812500) is a XR17V35X [ 1.221498] 0000:01:00.0: ttyS2 at MMIO 0x1100800 (irq = 334, base_baud = 7812500) is a XR17V35X [ 1.221896] 0000:01:00.0: ttyS3 at MMIO 0x1100c00 (irq = 334, base_baud = 7812500) is a XR17V35X [ 1.222587] 2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 26, base_baud = 5000000) is a IMX [ 1.223350] 21ec000.serial: ttymxc2 at MMIO 0x21ec000 (irq = 70, base_baud = 5000000) is a IMX [ 1.224122] 21f0000.serial: ttymxc3 at MMIO 0x21f0000 (irq = 71, base_baud = 5000000) is a IMX
Здорово. Работает.