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

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

Add Energy Efficient Ethernet (IEEE 802.3az) support to the Cadence GEM
(macb) driver. 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, as recommended by Microchip's GMAC documentation.

The series is structured as follows:

  1. Register definitions: LPI counter offsets (0x270-0x27c), TXLPIEN
     bitfield (NCR bit 19), and a 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: A delayed_work-based idle timer that enters LPI
     after 250ms of TX inactivity and wakes before transmit with a
     conservative 50us PHY wake delay. LPI entry is deferred 1 second
     after link-up per IEEE 802.3az.

  4. ethtool EEE ops: get_eee/set_eee delegating to phylink for PHY
     negotiation; the MAC-level TXLPIEN is controlled only from the
     phylink mac_link_up/mac_link_down callbacks.

  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 with iperf3 throughput/latency benchmarks,
ethtool --show-eee / --set-eee, ethtool -S LPI counter verification,
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      |  23 ++++
 drivers/net/ethernet/cadence/macb_main.c | 160 ++++++++++++++++++++++-
 2 files changed, 180 insertions(+), 3 deletions(-)

-- 
2.39.5