Re: [PATCH net-next v3 0/5] net: cadence: macb: add IEEE 802.3az EEE support

[Nicolai Buchwitz <nb@tipi-net.de>]

On 25.2.2026 10:15, Nicolai Buchwitz wrote:
> Add Energy Efficient Ethernet (IEEE 802.3az) support to the Cadence GEM
> (macb) driver using phylink's managed EEE framework. The GEM MAC has
> hardware LPI registers but no built-in idle timer, so the driver
> implements software-managed TX LPI using a delayed_work timer while
> delegating EEE negotiation and ethtool state to phylink.
> 
> Changes from v2:
>   - macb_tx_lpi_set() now returns bool indicating whether the register
>     value actually changed, avoiding redundant writes.
>   - Removed tx_lpi_enabled field from struct macb; LPI state is tracked
>     entirely within the spinlock-protected register read/modify/write.
>   - macb_tx_lpi_wake() uses the return value of macb_tx_lpi_set() to
>     skip the cancel/udelay when TXLPIEN was already clear.
>   All changes based on feedback from Russell King.
> 

Apologies for the missing subject prefix and version tags on this
series - should have been [PATCH net-next v3]. I'm still fairly new
to the kernel mailing list workflow and building up the muscle memory
around git-format-patch/send-email. I'll resend as v4 with the proper
tags. In the meantime, feedback on the code itself is very welcome.

> Changes from v1:
>   - Rewrote to use phylink managed EEE (mac_enable_tx_lpi /
>     mac_disable_tx_lpi callbacks) instead of the obsolete
>     phy_init_eee() approach, as recommended by Russell King.
>   - ethtool get_eee/set_eee are now pure phylink passthroughs.
>   - Removed all manual EEE state tracking from mac_link_up/down;
>     phylink handles the lifecycle.
> 
> The series is structured as follows:
> 
>   1. Register definitions: LPI counter offsets (0x270-0x27c), TXLPIEN
>      bitfield (NCR bit 19), and MACB_CAPS_EEE capability flag.
> 
>   2. LPI statistics: Expose the four hardware EEE counters (RX/TX LPI
>      transitions and time) through ethtool -S, accumulated in software
>      since they are clear-on-read.
> 
>   3. TX LPI engine: phylink mac_enable_tx_lpi / mac_disable_tx_lpi
>      callbacks with a delayed_work-based idle timer. LPI entry is
>      deferred 1 second after link-up per IEEE 802.3az. Wake before
>      transmit with a conservative 50us PHY wake delay.
> 
>   4. ethtool EEE ops: get_eee/set_eee delegating to phylink for PHY
>      negotiation and timer management.
> 
>   5. RP1 enablement: Set MACB_CAPS_EEE for the Raspberry Pi 5's RP1
>      southbridge (Cadence GEM_GXL rev 0x00070109 + BCM54213PE PHY).
> 
> Tested on Raspberry Pi 5 (1000BASE-T, BCM54213PE PHY, 250ms LPI timer):
> 
>   iperf3 throughput (no regression):
>     TCP TX: 937.8 Mbit/s (EEE on) vs 937.0 Mbit/s (EEE off)
>     TCP RX: 936.5 Mbit/s both
> 
>   Latency (ping RTT, small expected increase from LPI wake):
>     1s interval:  0.273 ms (EEE on) vs 0.181 ms (EEE off)
>     10ms interval: 0.206 ms (EEE on) vs 0.168 ms (EEE off)
>     flood ping:   0.200 ms (EEE on) vs 0.156 ms (EEE off)
> 
>   LPI counters (ethtool -S, 1s-interval ping, EEE on):
>     tx_lpi_transitions: 112
>     tx_lpi_time: 15574651
> 
>   Zero packet loss across all tests. Also verified with
>   ethtool --show-eee / --set-eee and cable unplug/replug cycling.
> 
> Nicolai Buchwitz (5):
>   net: cadence: macb: add EEE register definitions and capability flag
>   net: cadence: macb: add EEE LPI statistics counters
>   net: cadence: macb: implement EEE TX LPI support
>   net: cadence: macb: add ethtool EEE support
>   net: cadence: macb: enable EEE for Raspberry Pi RP1
> 
>  drivers/net/ethernet/cadence/macb.h      |  20 ++++
>  drivers/net/ethernet/cadence/macb_main.c | 136 ++++++++++++++++++++++-
>  2 files changed, 155 insertions(+), 1 deletion(-)

Nicolai