[ Adding Hans, Rafael, Rob and more people from the below thread. ] On Fri, Oct 26, 2018 at 08:57:22AM +0000, Einar Vading wrote: > Hi, > > I think that this could explain your problem: https://marc.info/?l=linux-acpi&m=152464754828003&w=2 > > "In short, when we added ACPI support to serdev, serdev started claiming > all slave devices to UARTs that happen to described by ACPI. Regardless > of whether there's a kernel driver for them or not." Right. > But I don't know if it is fixed. I'm afraid that discussion didn't go anywhere, so this hasn't been addressed as far as I know. Johan > ________________________________________ > Från: linux-serial-owner@xxxxxxxxxxxxxxx <linux-serial-owner@xxxxxxxxxxxxxxx> för Paul van Tilburg <paulvt@xxxxxxxxxx> > Skickat: den 25 oktober 2018 11:41 > Till: linux-serial@xxxxxxxxxxxxxxx > Ämne: Serial port of dw-abp-uart missing due to serial dev bus activation > > Dear all, > > This is a forward of a Debian bug report at the request of the Debian > kernel maintainers. The original bug report is located here: > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=911831 > > Since the upgrade of our system from Debian 9 (Stretch) to 10 (Buster), > but also from Ubuntu 16.04 LTS (Xenial) to 18.04 LTS (Bionic), the > serial port of our Atom E3950-based board can no longer be used. > > I have traced the cause to the enabling of CONFIG_SERIAL_DEV_BUS=y and > CONFIG_SERIAL_DEV_CTRL_TTYPORT=y in the kernel config of versions > 4.17.0-3 (Debian) and 4.15.0.36.38 (Ubuntu). > > In a working system the dw-abp-uart driver exposes two tty devices: > > # dmesg | grep tty > [ 2.437836] dw-apb-uart.2: ttyS0 at MMIO 0x8121c000 (irq = 4, base_baud = 115200) is a 16550A > [ 2.439193] dw-apb-uart.3: ttyS1 at MMIO 0x8121a000 (irq = 6, base_baud = 115200) is a 16550A > > of which we always use ttyS1. (I do not know why ttyS0 does nothing, > supposedly this system has only one UART?) The corresponding udev info > is: > > looking at device '/devices/pci0000:00/0000:00:18.0/dw-apb-uart.2/tty/ttyS0': > KERNEL=="ttyS0" > SUBSYSTEM=="tty" > DRIVER=="" > > looking at parent device '/devices/pci0000:00/0000:00:18.0/dw-apb-uart.2': > KERNELS=="dw-apb-uart.2" > SUBSYSTEMS=="platform" > DRIVERS=="dw-apb-uart" > ATTRS{driver_override}=="(null)" > > looking at parent device '/devices/pci0000:00/0000:00:18.0': > KERNELS=="0000:00:18.0" > SUBSYSTEMS=="pci" > DRIVERS=="intel-lpss" > ATTRS{ari_enabled}=="0" > ATTRS{broken_parity_status}=="0" > ATTRS{class}=="0x118000" > ATTRS{consistent_dma_mask_bits}=="32" > ATTRS{d3cold_allowed}=="1" > ATTRS{device}=="0x5abc" > ATTRS{dma_mask_bits}=="32" > ATTRS{driver_override}=="(null)" > ATTRS{enable}=="1" > ATTRS{index}=="9" > ATTRS{irq}=="4" > ATTRS{label}=="Onboard - Other" > ATTRS{local_cpulist}=="0-3" > ATTRS{local_cpus}=="f" > ATTRS{msi_bus}=="1" > ATTRS{numa_node}=="-1" > ATTRS{revision}=="0x0b" > ATTRS{subsystem_device}=="0x7270" > ATTRS{subsystem_vendor}=="0x8086" > ATTRS{vendor}=="0x8086" > > looking at device '/devices/pci0000:00/0000:00:18.2/dw-apb-uart.3/tty/ttyS1': > KERNEL=="ttyS1" > SUBSYSTEM=="tty" > DRIVER=="" > > looking at parent device '/devices/pci0000:00/0000:00:18.2/dw-apb-uart.3': > KERNELS=="dw-apb-uart.3" > SUBSYSTEMS=="platform" > DRIVERS=="dw-apb-uart" > ATTRS{driver_override}=="(null)" > > looking at parent device '/devices/pci0000:00/0000:00:18.2': > KERNELS=="0000:00:18.2" > SUBSYSTEMS=="pci" > DRIVERS=="intel-lpss" > ATTRS{ari_enabled}=="0" > ATTRS{broken_parity_status}=="0" > ATTRS{class}=="0x118000" > ATTRS{consistent_dma_mask_bits}=="32" > ATTRS{d3cold_allowed}=="1" > ATTRS{device}=="0x5ac0" > ATTRS{dma_mask_bits}=="32" > ATTRS{driver_override}=="(null)" > ATTRS{enable}=="1" > ATTRS{index}=="10" > ATTRS{irq}=="6" > ATTRS{label}=="Onboard - Other" > ATTRS{local_cpulist}=="0-3" > ATTRS{local_cpus}=="f" > ATTRS{msi_bus}=="1" > ATTRS{numa_node}=="-1" > ATTRS{revision}=="0x0b" > ATTRS{subsystem_device}=="0x7270" > ATTRS{subsystem_vendor}=="0x8086" > ATTRS{vendor}=="0x8086" > > > looking at parent device '/devices/pci0000:00': > KERNELS=="pci0000:00" > SUBSYSTEMS=="" > DRIVERS=="" > > However, when the serial device bus with the serial TTY control port is > enabled, ttyS1 disappears: > > # dmesg | grep tty > [ 2.499748] dw-apb-uart.2: ttyS0 at MMIO 0x8121c000 (irq = 4, base_baud = 115200) is a 16550A > [ 2.500852] dw-apb-uart.3: ttyS1 at MMIO 0x8121a000 (irq = 6, base_baud = 115200) is a 16550A > [ 2.500996] serial serial0: tty port ttyS1 registered > > The difference in the udev info is: > > looking at device '/devices/pci0000:00/0000:00:18.2/dw-apb-uart.3/serial0/serial0-0': > KERNEL=="serial0-0" > SUBSYSTEM=="serial" > DRIVER=="" > > looking at parent device '/devices/pci0000:00/0000:00:18.2/dw-apb-uart.3/serial0': > KERNELS=="serial0" > SUBSYSTEMS=="serial" > DRIVERS=="" > > and there is no longer tty under /sys/devices/pci0000:00/0000:00:18.2/dw-apb-uart.3. > > Attached is the full dmesg output for the broken tty port instance. Let > me know if more information is required. > > I must also note that I am currently not a list member and am not very > knowledgeable about the serial interface internals, so feel free to > point me to any further reading to understand what is going on under the > hood. > > Kind regards, > Paul van Tilburg
