JorgeGzm opened a new pull request, #19930:
URL: https://github.com/apache/nuttx/pull/19930
## Summary
Two independent fixes to the STM32H7 Ethernet driver, split out of #19911
at review request.
**Never transmit a reply into a full TX ring**
`stm32_receive()` replies to ARP, IPv4 and IPv6 straight from the RX path
without checking whether a TX descriptor is free. Under sustained load the
reply overwrites a descriptor the DMA still owns and the link stalls until
the interface is reset.
All three reply paths now check `stm32_txringfull()` first. That check has
to consider `des0` as well as the OWN bit: a descriptor already consumed by
the DMA but not yet reclaimed still has its buffer pointer set, and
treating it as free is what corrupts the ring.
**Allow restricting autonegotiation to 10BASE-T full duplex**
New `CONFIG_STM32_AUTONEG_10FD_ONLY`, default n. On a board whose display
generates enough noise to corrupt 100BASE-TX, throughput collapses with
whatever is on the screen. Advertising only 10BASE-T full duplex makes both
ends negotiate a link that survives the interference.
It advertises rather than forcing the MCR, so the two ends still agree. A
forced setting on one side produces a duplex mismatch, which looks exactly
like a bad cable and is much harder to diagnose.
## Impact
No functional change for existing users. Both are confined to
`arch/arm/src/stm32h7/stm32_ethernet.c` and the shared
`arch/arm/src/common/stm32/Kconfig.eth`; the new option defaults to n, so
nothing changes unless a board opts in.
The TX ring guard costs one descriptor read per received packet that gets
a reply.
## Testing
Host: Linux, arm-none-eabi-gcc 13.2.
Board: linum-stm32h753bi (STM32H753BI, 1024x600 RGB panel), `netnsh`.
TX ring: sustained ping flood and TCP transfer while the panel was being
redrawn. Before the change the link stalled and only a reset recovered it.
After, the interface stayed up for the whole run.
Autonegotiation: measured throughput with the panel showing static content
against animated content.
nsh> ifconfig
eth0 Link encap:Ethernet HWaddr 00:e0:de:ad:be:ef at RUNNING mtu 1486
inet addr:192.168.15.4 DRaddr:192.168.15.1 Mask:255.255.255.0
stm32_eth: link full-duplex 100 Mbps (default)
stm32_eth: link full-duplex 10 Mbps
(CONFIG_STM32_AUTONEG_10FD_ONLY=y)
With 100BASE-TX the transfer rate varied by up to 200x depending on screen
content. With the option enabled the link is slower on paper and steady in
practice.
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