diff options
Diffstat (limited to 'Documentation/misc-devices/aspeed-uart-routing.txt')
| -rw-r--r-- | Documentation/misc-devices/aspeed-uart-routing.txt | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/misc-devices/aspeed-uart-routing.txt b/Documentation/misc-devices/aspeed-uart-routing.txt new file mode 100644 index 000000000000..cf1c2a466875 --- /dev/null +++ b/Documentation/misc-devices/aspeed-uart-routing.txt @@ -0,0 +1,49 @@ +Kernel driver aspeed-uart-routing +================================= + +Supported chips: +ASPEED AST2500/AST2600 + +Author: +Google LLC + +Description +----------- + +The Aspeed AST2500/AST2600 allows to dynamically route the inputs for the +built-in UARTS and physical serial I/O ports. + +This allows, for example, to connect the output of UART to another UART. +This can be used to enable host<->BMC communication via UARTs, e.g. to allow +access to the host's serial console. + +This driver is for the BMC side. The sysfs files allow the BMC userspace +which owns the system configuration policy, to configure how UARTs and +physical serial I/O ports are routed. + +The driver provides the following files in sysfs: +uart1 Configure the input signal to UART1. +uart2 Configure the input signal to UART2. +uart3 Configure the input signal to UART3. +uart4 Configure the input signal to UART4. +uart5 Configure the input signal to UART5. +io1 Configure the input signal to physical serial port 1. +io2 Configure the input signal to physical serial port 2. +io3 Configure the input signal to physical serial port 3. +io4 Configure the input signal to physical serial port 4. +io5 Configure the input signal to physical serial port 5. + +When read, each file shows the list of available options with the currently +selected option marked by square brackets "[]". The list of available options +depends on the selected file. + +Example: +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 +[io1] io2 io3 io4 uart2 uart3 uart4 io6 + +In this case, UART1 gets its input signal from IO1 (physical serial port 1). + +$ echo -n "uart3" \ + >/sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1 +io1 io2 io3 io4 uart2 [uart3] uart4 io6 |