cpu/efm32: add ethernet driver

[basilfx]

Contribution description

Note

Development of this PR happens in parallel to the LPC1768 ethernet driver in #22305. Any feedback on this one is likely applicable to the other one as well. I will try to keep both PRs in sync where it matters.

This PR adds an ethernet driver for the EFM32. While working on the LPC1768 version, I decided to also add support for the EFM32.

What is provided:

• Low-level driver with netdev driver on top of it.
• Separate modules (efm32_eth_link_up, efm32_eth_auto) like the STM32.
• lwIP/GNRC auto-initialization.
• Kconfig tunables for buffers/timeouts/etc.

Testing procedure

The only EFM32 board with ethernet in RIOT's code base, is the SLSTK3701a.

Like the LPC1768 ethernet driver, I would rather receive feedback on the general structure and adoption. I will then do my best to collect as much evidence as possible.

Testing has been performed as follows:

• Compile tests (mixes options and toolchains, see below)
• Benchmark UDP
• Driver test in tests/drivers/efm32_eth
• Ping test (including fragmentation and large frames, >12 hours)
• lwIP iPerf (depends on examples/networking/misc/lwiperf: add application #22286).
• IPv4/IPv6.
• Monkey testing (link up/down etc).

Based on this, I believe it is in a working state.

With efm32_eth_auto enabled, the link speed is ~7.5-10 MBit/sec (measured using lwIP iPerf).

Compile test

#!/bin/sh

set -e

BOARD=slstk3701a make -C tests/drivers/efm32_eth -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_link_up make -C tests/drivers/efm32_eth -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_auto make -C tests/drivers/efm32_eth -j 14

BOARD=slstk3701a make -C examples/networking/misc/benchmark_udp -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_link_up make -C examples/networking/misc/benchmark_udp -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_auto make -C examples/networking/misc/benchmark_udp -j 14

BOARD=slstk3701a LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14

# lwIP IPerf application is still a PR
# BOARD=slstk3701a LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14
# BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14
# BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14

BOARD=slstk3701a LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14
BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14

TOOLCHAIN=llvm BOARD=slstk3701a make -C tests/drivers/efm32_eth -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_link_up make -C tests/drivers/efm32_eth -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_auto make -C tests/drivers/efm32_eth -j 14

TOOLCHAIN=llvm BOARD=slstk3701a make -C examples/networking/misc/benchmark_udp -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_link_up make -C examples/networking/misc/benchmark_udp -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_auto make -C examples/networking/misc/benchmark_udp -j 14

TOOLCHAIN=llvm BOARD=slstk3701a LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP=1 make -C examples/networking/misc/benchmark_udp -j 14

# lwIP IPerf application is still a PR
# TOOLCHAIN=llvm BOARD=slstk3701a LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14
# TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14
# TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/networking/misc/lwiperf -j 14

TOOLCHAIN=llvm BOARD=slstk3701a LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_link_up LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14
TOOLCHAIN=llvm BOARD=slstk3701a USEMODULE=efm32_eth_auto LWIP_IPV4=1 LWIP_IPV6=1 make -C examples/basic/default -j 14

Issues/PRs references

None

Declaration of AI-Tools / LLMs usage:

AI-Tools / LLMs that were used are:

• Claude Code generated the first (non-working) version of the driver in cpu/efm32. I then refined, reworked and tested it myself. I did ask Claude Code to analyze bugs I encountered during testing. The final PR review was also done with Claude Code, but changes were applied manually. The test application, auto-init adoption and several other parts are simply copy-paste of existing drivers.

[riot-ci]

Murdock results

❌ FAILED

0f63ccf features: add efm32_eth to features

Success	Failures	Total	Runtime
2463	0	10343	03m:59s

Artifacts

[benpicco]

Looking good, just some nits

[basilfx]

Some comments on the LPC1768 driver also apply here, so I will do some minor fixups to align both drivers next week. Thanks @benpicco.

[basilfx]

Update on the preliminary test results: a ping test with 16-byte increases up to 2048 bytes has been running non-stop for the past two-ish weeks. Apart from a few switch reboots (UniFi stuff), the MCU did not crash/reboot.

[basilfx]

@benpicco I think I have covered all comments so far. Can I do an intermediate squash?

Mean while, I will start with final testing. Now that the lwiperf example is in, I can also do some 'load' tests.

[benpicco]

Sure, please squash

[basilfx]

Update on the test reults: #22305 (comment)

[basilfx]

@benpicco the last three fixup commits are the changes I did since the intermediate squash. Most of them are a consequence of the changes I did to the LPC1768 driver too.

This branch is currently tested again.

[basilfx]

Adding wait for PR because #22305 must be merged first, and #22344 too.

[basilfx]

Hmm, this seems to fail due to config.h being included via periph_cpu.c, that contains static_assert(..).

Guess that this is somewhat related to #9371 and MicroPython not using -std=c11 yet. See if we can fix that :-)