Hello,
I noticed an issue with the following USB to serial adapter when
autosuspend is enabled for that device:
ID 04b4:0008 Cypress Semiconductor Corp. CDC ACM serial port
The problem is that the device silently drops any data received from
the serial connection whenever there is a pause in communication for
longer than one or two seconds. Then one needs to either touch the
device (e.g., /dev/ttyACM0) or send some characters via USB to receive
data again.
The problem can be circumvented by the following udev rule:
ACTION=="add|change", SUBSYSTEM=="usb", ATTR{idVendor}=="04b4", ATTR{idProduct}=="0008", TEST=="power/control", ATTR{power/control}="on"
Is this something that should already be applied by the kernel?
I'm running Linux 6.1.8. Below you find outputs of lspci and lsusb for
the relevant devices.
lspci -v for the USB controler:
06:00.4 USB controller: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne USB 3.1 (prog-if 30 [XHCI])
Subsystem: Lenovo Device 5082
Flags: bus master, fast devsel, latency 0, IRQ 75, IOMMU group 7
Memory at fd100000 (64-bit, non-prefetchable) [size=1M]
Capabilities: [48] Vendor Specific Information: Len=08 <?>
Capabilities: [50] Power Management version 3
Capabilities: [64] Express Endpoint, MSI 00
Capabilities: [a0] MSI: Enable- Count=1/8 Maskable- 64bit+
Capabilities: [c0] MSI-X: Enable+ Count=8 Masked-
Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
Kernel driver in use: xhci_hcd
Kernel modules: xhci_pci
lsusb -v for the USB device:
Bus 006 Device 010: ID 04b4:0008 Cypress Semiconductor Corp. CDC ACM serial port
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 2 Communications
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x04b4 Cypress Semiconductor Corp.
idProduct 0x0008 CDC ACM serial port
bcdDevice 0.00
iManufacturer 1 2012 Cypress Semiconductor
iProduct 2 Cypress-USB2UART-Ver1.0G
iSerial 4 827211C2091B
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x0043
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 3 USB-UART Configuration
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 2 Communications
bInterfaceSubClass 2 Abstract (modem)
bInterfaceProtocol 1 AT-commands (v.25ter)
iInterface 0
CDC Header:
bcdCDC 1.10
CDC ACM:
bmCapabilities 0x02
line coding and serial state
CDC Union:
bMasterInterface 0
bSlaveInterface 1
CDC Call Management:
bmCapabilities 0x00
bDataInterface 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0010 1x 16 bytes
bInterval 2
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 10 CDC Data
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x03 EP 3 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0000
(Bus Powered)
Best regards,
Michael
