cpu/sam4s: add initial support with SAM4S-XPRO board

[dylad]

Contribution description

This PR adds initial support for SAM4s MCUs from Microchip (formerly Atmel) and its sam4s-xpro board.
There are a bit old already, but still produced by Microchip and their headers files are already in-tree.

This family is pretty close to SAM3 (which we already support through arduino-due) except that this is a Cortex-M4 which runs a little faster.

Since peripherals are the same, I've moved GPIOs, Timer and UART driver to cpu/sam_common.
I plan to move the remaining drivers (if relevant) in followup PRs.

Testing procedure

Get a sam4s-xpro and run any tests involving UART/Timers/GPIOs.

For the record here is the output of tests/sys/shell running on sam4s-xpro:

make BOARD=sam4s-xpro -C tests/sys/shell flash term                          INT ✘  1m 4s 
make: Entering directory '/home/dylan/work/RIOT/tests/sys/shell'
Building application "tests_shell" for "sam4s-xpro" with CPU "sam4s".

"make" -C /home/dylan/work/RIOT/pkg/cmsis/ 
"make" -C /home/dylan/work/RIOT/boards/common/init
"make" -C /home/dylan/work/RIOT/boards/sam4s-xpro
"make" -C /home/dylan/work/RIOT/core
"make" -C /home/dylan/work/RIOT/core/lib
"make" -C /home/dylan/work/RIOT/cpu/sam4s
"make" -C /home/dylan/work/RIOT/cpu/cortexm_common
"make" -C /home/dylan/work/RIOT/cpu/cortexm_common/periph
"make" -C /home/dylan/work/RIOT/cpu/sam4s/periph
"make" -C /home/dylan/work/RIOT/cpu/sam_common
"make" -C /home/dylan/work/RIOT/cpu/sam_common/periph
"make" -C /home/dylan/work/RIOT/drivers
"make" -C /home/dylan/work/RIOT/drivers/periph_common
"make" -C /home/dylan/work/RIOT/sys
"make" -C /home/dylan/work/RIOT/sys/app_metadata
"make" -C /home/dylan/work/RIOT/sys/auto_init
"make" -C /home/dylan/work/RIOT/sys/div
"make" -C /home/dylan/work/RIOT/sys/frac
"make" -C /home/dylan/work/RIOT/sys/isrpipe
"make" -C /home/dylan/work/RIOT/sys/libc
"make" -C /home/dylan/work/RIOT/sys/malloc_thread_safe
"make" -C /home/dylan/work/RIOT/sys/newlib_syscalls_default
"make" -C /home/dylan/work/RIOT/sys/preprocessor
"make" -C /home/dylan/work/RIOT/sys/ps
"make" -C /home/dylan/work/RIOT/sys/shell
"make" -C /home/dylan/work/RIOT/sys/shell/cmds
"make" -C /home/dylan/work/RIOT/sys/stdio
"make" -C /home/dylan/work/RIOT/sys/stdio_uart
"make" -C /home/dylan/work/RIOT/sys/test_utils/interactive_sync
"make" -C /home/dylan/work/RIOT/sys/test_utils/print_stack_usage
"make" -C /home/dylan/work/RIOT/sys/tsrb
"make" -C /home/dylan/work/RIOT/sys/ztimer
  text    data     bss     dec     hex filename
 13008     160    2820   15988    3e74 /home/dylan/work/RIOT/tests/sys/shell/bin/sam4s-xpro/tests_shell.elf
/home/dylan/work/RIOT/dist/tools/openocd/openocd.sh flash /home/dylan/work/RIOT/tests/sys/shell/bin/sam4s-xpro/tests_shell.elf
### Flashing Target ###
Open On-Chip Debugger 0.12.0
Licensed under GNU GPL v2
For bug reports, read
       http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport "swd". To override use 'transport select <transport>'.
Info : CMSIS-DAP: SWD supported
Info : CMSIS-DAP: FW Version = 02.01.0157
Info : CMSIS-DAP: Serial# = ATML1803040200000875
Info : CMSIS-DAP: Interface Initialised (SWD)
Info : SWCLK/TCK = 1 SWDIO/TMS = 1 TDI = 1 TDO = 1 nTRST = 0 nRESET = 1
Info : CMSIS-DAP: Interface ready
Info : clock speed 500 kHz
Info : SWD DPIDR 0x2ba01477
Info : [ATSAM4SD32C.cpu] Cortex-M4 r0p1 processor detected
Info : [ATSAM4SD32C.cpu] target has 6 breakpoints, 4 watchpoints
Info : starting gdb server for ATSAM4SD32C.cpu on 0
Info : Listening on port 46877 for gdb connections
   TargetName         Type       Endian TapName            State       
--  ------------------ ---------- ------ ------------------ ------------
0* ATSAM4SD32C.cpu    cortex_m   little ATSAM4SD32C.cpu    running

[ATSAM4SD32C.cpu] halted due to debug-request, current mode: Thread 
xPSR: 0x01000000 pc: 0x00400784 msp: 0x20000200
Info : sam4 does not auto-erase while programming (Erasing relevant sectors)
Info : sam4 First: 0x00000000 Last: 0x00000001
Info : Erasing sector: 0x00000000
Info : Erasing sector: 0x00000001
auto erase enabled
wrote 16384 bytes from file /home/dylan/work/RIOT/tests/sys/shell/bin/sam4s-xpro/tests_shell.elf in 1.024621s (15.616 KiB/s)

verified 13168 bytes in 0.613142s (20.973 KiB/s)

shutdown command invoked
Done flashing
/home/dylan/work/RIOT/dist/tools/pyterm/pyterm -p "/dev/ttyACM0" -b "115200" -ln "/tmp/pyterm-dylan" -rn "2025-02-08_13.46.12-tests_shell-sam4s-xpro"  
Twisted not available, please install it if you want to use pyterm's JSON capabilities
2025-02-08 13:46:12,211 # Connect to serial port /dev/ttyACM0
Welcome to pyterm!
Type '/exit' to exit.
2025-02-08 13:46:13,730 # main(): This is RIOT! (Version: 2025.04-devel-89-g2f0cb-pr/cpu/sam4s/add_support)
2025-02-08 13:46:13,731 # test_shell.
> ps
2025-02-08 13:46:15,345 # ps
2025-02-08 13:46:15,347 #       pid | state    Q | pri 
2025-02-08 13:46:15,349 #         1 | running  Q |   7
> help
2025-02-08 13:46:17,646 # help
2025-02-08 13:46:17,649 # Command              Description
2025-02-08 13:46:17,652 # ---------------------------------------
2025-02-08 13:46:17,656 # bufsize              Get the shell's buffer size
2025-02-08 13:46:17,659 # start_test           starts a test
2025-02-08 13:46:17,662 # end_test             ends a test
2025-02-08 13:46:17,666 # echo                 prints the input command
2025-02-08 13:46:17,670 # empty                print nothing on command
2025-02-08 13:46:17,674 # periodic             periodically print command
2025-02-08 13:46:17,678 # xfa_test1            xfa test command 1
2025-02-08 13:46:17,682 # xfa_test2            xfa test command 2
2025-02-08 13:46:17,686 # app_metadata         Returns application metadata
2025-02-08 13:46:17,690 # pm                   interact with layered PM subsystem
2025-02-08 13:46:17,696 # ps                   Prints information about running threads.
2025-02-08 13:46:17,700 # version              Prints current RIOT_VERSION
2025-02-08 13:46:17,704 # reboot               Reboot the node
> periodic
2025-02-08 13:46:20,555 # periodic
> 2025-02-08 13:46:21,055 # test
2025-02-08 13:46:21,556 # test
2025-02-08 13:46:22,056 # test
2025-02-08 13:46:22,556 # test
2025-02-08 13:46:23,056 # test

Issues/PRs references

None.

[crasbe]

I don't have the hardware to test this, but just two things I noticed while glancing over this.

[riot-ci]

Murdock results

✔️ PASSED

363fb75 boards/sam4s-xpro: introduce initial board support

Success	Failures	Total	Runtime
10271	0	10271	09m:03s

Artifacts

• Documentation preview

[dylad]

static-tests are happy !

[benpicco]

Looks good to me, feel free to squash!

[dylad]

I've addressed @benpicco's comments and squashed.

[dylad]

Ah Murdock catches something.
I'll fix it later today.