Introduction

The UART operations are controlled by the configuration and mode registers. The state of the FIFOs, modem signals, and other controller functions are read using the status, interrupt
status, and modem status registers.The controller is structured with separate RX and TX data paths. Each path includes a 64-byte FIFO. The controller serializes and deserializes data
in the TX and RX FIFOs and includes a mode switch to support various loopback configurations for the RxD and TxD signals. The FIFO interrupt status bits support polling or interrupt
driven handler. Software reads and writes data bytes using the RX and TX data port registers.When using the UART in a modem-like application, the modem control module detects and
generates the modem handshake signals and also controls the receiver and transmitter paths according to the handshaking protocol.
The PS Uart is in Zynq Ultrascale+ MpSoC and Zynq platforms.

HW IP Features

Programmable baud rate generator
64-byte receive and transmit FIFOs
Programmable protocol:° 6, 7, or 8 data bits 1, 1.5, or 2 stop bits
Odd, even, space, mark, or no parity
Parity, framing and overrun error detection
Line-break generation and detection
Interrupts generation
Automatic echo, local loopback, and remote loopback channel modes
Modem control signals: CTS, RTS, DSR, DTR, RI, and DCD

Features supported in driver

Programmable baud rate generator
64-byte receive and transmit FIFOs
Programmable protocol:° 6, 7, or 8 data bits 1, 1.5, or 2 stop bits
Odd, even, space, mark, or no parity
Parity, framing and overrun error detection
Line-break generation and detection
Interrupts generation
Automatic echo, local loopback, and remote loopback channel modes
Modem control signals: CTS, RTS, DSR, DTR, RI, and DCD

Missing Features, Known Issues and Limitations

None

Kernel Configuration

To enable the uart driver in the linux kernel you either have to integrate it or build it as kernel module (.ko). you can enable it with:

CONFIG_SERIAL_XILINX_PS_UART=y
CONFIG_SERIAL_XILINX_PS_UART_CONSOLE=y

When more than two UARTs are required in the system (including PL UARTs) the user should also configure the following configuration item to increase the number of UART ports.
The driver statically allocates port data structures based on this configuration item. A kernel error similar to "Cannot get uart_port structure" may be seen during kernel boot when this is an issue.

CONFIG_SERIAL_XILINX_NR_UARTS=<number of expected UARTs>

Devicetree
Here's how the devicetree entry could look like.

https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/cdns%2Cuart.txt

        uart0: serial@e0000000 {
            compatible = "xlnx,xuartps", "cdns,uart-r1p8";
            clocks = <&clkc 23>, <&clkc 40>;
            clock-names = "uart_clk", "pclk";
            reg = <0xE0000000 0x1000>;
            interrupts = <0 27 4>;
        };

Test procedure

stty-Linux Commands Related to configuration and Testing:

stty -all --> command can be used to display the terminal configuration parameters of a tty device. To display all of the active settings on a tty device.
stty -F /dev/ttyPS0 crtscts /-crtscts) --> Enable/Disable hardware handshaking.
stty -F /dev/ttyPS0 ixon / -ixon --> Enable/Disable XON/XOFF flow control.
stty -F /dev/ttyPS0 clocal / -clocal --> Enable/Disable modem control signals such as DTR/DTS and DCD. This is necessary if you are using a "three wire" serial cable because it does not supply these signals.
stty -F /dev/ttyPS0 cs5 / cs6 / cs7 / cs8 --> Set number of data bits to 5, 6, 7, or 8, respectively.
stty -F /dev/ttyPS0 parodd / -parodd --> Enable odd parity. Disabling this flag enables even parity.
stty -F /dev/ttyPS0 parenb / -parenb --> Enable parity checking. When this flag is negated, no parity is used.
stty -F /dev/ttyPS0 cstopb / -cstopb --> Enable use of two stop bits per character. When this flag is negated, one stop bit per character is used.
stty -F /dev/ttyPS0 echo / -echo --> Enable/Disable echoing of received characters back to sender.

UART BREAK DETECTION:

To test the Uart break detection the above setup is required.
Connect the ep108 serial port with PC serial port with the help of either DB 9 connector or USB to serial cable.
Form PC side with the help of Tera term application go to following options and issue the break signal.
- Contol ----> Send break or Alt + B
With the help of proc file system (proc/tty/driver/xuartps) we can check whether the board serial port is receiving the break signal or not.

root@Xilinx-ZynqMP-EAApr2015:~# cat  /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:16 tx:21556 rx:401 brk:1 RTS|CTS|DTR|DSR|CD

Expected Output

root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:1008 rx:51 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:0 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# [   79.344585] sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) sync(s) show-task-states(t) unmount(u) show-blocked-tasks(w) dump-ftrace-buffer(z)
 
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:1267 rx:64 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:0 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# stty -F /dev/ttyPS0 -a
speed 115200 baud;stty: /dev/ttyPS0
 line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol =
; eol2 = <undef>;
swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon -iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke
root@Xilinx-ZCU102-2015_4:~# stty -F /dev/ttyPS1 -a
speed 9600 baud;stty: /dev/ttyPS1
 line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:2975 rx:162 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:1 brk:1 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# stty -F /dev/ttyPS1 inpck
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:3646 rx:200 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:2 fe:1 brk:1 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:4042 rx:215 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:7 fe:6 brk:1 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# stty -F /dev/ttyPS1 parenb
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:4835 rx:263 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:8 fe:6 pe:1 brk:1 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:5236 rx:278 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:9 fe:6 pe:1 brk:2 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~# cat < /dev/ttyPS1[  363.850712] random: nonblocking pool is initialized
 
^C
root@Xilinx-ZCU102-2015_4:~# cat /proc/tty/driver/xuartps
serinfo:1.0 driver revision:
0: uart:xuartps mmio:0xFF000000 irq:204 tx:5637 rx:293 brk:1 RTS|CTS|DTR|DSR|CD
1: uart:xuartps mmio:0xFF010000 irq:205 tx:0 rx:13 fe:6 pe:5 brk:2 CTS|DSR|CD
root@Xilinx-ZCU102-2015_4:~#

Mainline status

The below commits needs to be upstream
- 2e5cc8e serial: xuartps: Fix the early_console junk character issue.
- 0cd0559 serial: xuartps: Fix the error handling logic in probe().
- 0f44bb0 tty: serial: Added a CONFIG_SERIAL_XILINX_NR_UARTS option.

Change Log

2016.3
Summary:

tty: serial: xuartps: Wait for rx and tx done status

Commits:

0db7a24 tty: serial: xuartps: Wait for rx and tx done status

2016.4

None

2017.1
Summary:

serial: xuartps: Enable uart loopback mode
tty: serial: xilinx: Use mainline driver version
serial: xuartps: Fix interrupt mask issue to handle the RX interrupts properly.
serial: xilinx_uartps: Add pm runtime support
serial: xuartps: Fix the early_console junk character issue
serial: xuartps: Cleanup the clock enable
serial: xuartps: Enable clocks in the pm disable case
serial: xuartps: Enable uart loopback mode
serial: xuartps: Fix the error handling logic in probe().
tty: serial: Added a CONFIG_SERIAL_XILINX_NR_UARTS option.

Commits:

6226051 serial: xuartps: Enable uart loopback mode
25c25a1 tty: serial: xilinx: Use mainline driver version
a96b8d2 serial: xuartps: Fix interrupt mask issue to handle the RX interrupts properly.
870d6d6 serial: xilinx_uartps: Add pm runtime support
2e5cc8e serial: xuartps: Fix the early_console junk character issue
f26b7ab serial: xuartps: Cleanup the clock enable
7bf059f serial: xuartps: Enable clocks in the pm disable case
9fb8e58 serial: xuartps: Enable uart loopback mode
0cd0559 serial: xuartps: Fix the error handling logic in probe().
0f44bb0 tty: serial: Added a CONFIG_SERIAL_XILINX_NR_UARTS option.

2017.2

None

2017.3
Summary:

serial: xilinx_uartps: Fix kernel doc warnings
serial: xilinx_uartps: Fix warnings in the driver

Commits:

0240098 serial: xilinx_uartps: Fix kernel doc warnings
6ba85c7 serial: xilinx_uartps: Fix warnings in the driver

2017.4
Summary:

tty: xilinx_uartps: move to arch_initcall for earlier console

Commits:

ea9d34b tty: xilinx_uartps: move to arch_initcall for earlier console

2018.1
Summary:

serial: xilinx_uartps: Add pm runtime support

Commits:

d62100f serial: xilinx_uartps: Add pm runtime support

2018.2

None

2018.3
Summary:

serial: xuartps: Enable clocks in the pm disable case also
serial: xuartps: Enable uart loopback mode
serial: uartps: Fix kernel doc warnings
tty: xilinx_uartps: move to arch_initcall for earlier console
tty: xilinx_uartps: Enable automatic flow control
serial: uartps: Use dynamic array for console port
serial: uartps: Move cnds_uart_get_port to probe
serial: uartps: Remove static port array
serial: uartps: Do not use static struct uart_driver out of probe()
serial: uartps: Move alias reading higher in probe()
serial: uartps: Change logic how console_port is setup
serial: uartps: Register own uart console and driver structures
serial: uartps: Change uart ID port allocation
serial: uartps: Check if the device is a console

Commits:

7bf059fserial: xuartps: Enable clocks in the pm disable case also
9fb8e58serial: xuartps: Enable uart loopback mode
94094a9 serial: uartps: Fix kernel doc warnings
ea9d34btty: xilinx_uartps: move to arch_initcall for earlier console
5d29fa5tty: xilinx_uartps: Enable automatic flow control
2288a8eserial: uartps: Use dynamic array for console port
47fe24d serial: uartps: Move cnds_uart_get_port to probe
8d2b924serial: uartps: Remove static port array
317f163serial: uartps: Do not use static struct uart_driver out of probe()
b09b499serial: uartps: Move alias reading higher in probe()
00639b5 serial: uartps: Change logic how console_port is setup
2f65317serial: uartps: Register own uart console and driver structures
906433dserial: uartps: Change uart ID port allocation
9ec4aaeserial: uartps: Check if the device is a console

2019.1
Summary:
- serial: uartps: Fix stuck ISR if RX disabled with non-empty FIFO
- serial: xuartps: fix typo in cdns_uart_startup
- serial: xuartps: reduce hardware TX race condition
- serial: xuartps: remove unnecessary register write
- serial: uartps: Remove console_initcall from the driver
- serial: uartps: Move cnds_uart_get_port to probe
- of: base: Change logic in of_alias_get_alias_list()
- serial: uartps: Do not allow use aliases >= MAX_UART_INSTANCES
- serial: uartps: Fix the ignore_status
- serial: uartps: Add support for cts-override

Commits:

d5d53b4serial: uartps: Fix stuck ISR if RX disabled with non-empty FIFO
22032cserial: xuartps: fix typo in cdns_uart_startup
de4ed39serial: xuartps: reduce hardware TX race condition
b41609aserial: xuartps: remove unnecessary register write
7a3741serial: uartps: Remove console_initcall from the driver
1f21072serial: uartps: Move cnds_uart_get_port to probe
e03af1of: base: Change logic in of_alias_get_alias_list()
41cdfeaserial: uartps: Do not allow use aliases >= MAX_UART_INSTANCES

fc5337serial: uartps: Fix the ignore_status
0f3d182serial: uartps: Add support for cts-override

2019.2
Summary:
serial: uartps: Move to fixed major number for uart
serial: uartps: Move the spinlock after the read of the tx empty
serial: uartps: Add a timeout to the tx empty wait
serial: uartps: Prevent writes when the controller is disabled
Commits:
2020.1

Summary:

tty: xilinx_uartps: Add the id to the console
serial: uartps: Use cdns_uart_tx_empty in console_write
serial: uartps: Wait for tx_empty in console setup
serial: uartps: Revert dynamic port allocation
serial: uartps: Add TACTIVE check in cdns_uart_tx_empty function
serial: uartps: Remove unconditional wait inside set_termios

Commits:

2020.2

Summary:

Revert "tty: xilinx_uartps: Fix missing id assignment to the console"
tty: xilinx_uartps: Really fix id assignment

Commits:

PS UART

Introduction

HW IP Features

Features supported in driver

Missing Features, Known Issues and Limitations

Kernel Configuration

Test procedure

Expected Output

Mainline status

Change Log

Related Links