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 v4:
- Removed redundant MACB_CAPS_EEE guards from macb_get_eee/set_eee;
phylink already returns -EOPNOTSUPP when lpi_capabilities and
lpi_interfaces are not populated. Based on feedback from Russell King.
- Added patch 5 enabling EEE for Mobileye EyeQ5, tested by Théo Lebrun
using a hardware loopback.
Changes from v3:
- Dropped the register-definitions-only patch; LPI counter offsets
(GEM_RXLPI/RXLPITIME/TXLPI/TXLPITIME) now land in the statistics
patch, and TXLPIEN + MACB_CAPS_EEE are introduced alongside the TX
LPI implementation where they are first used. Series is now 4 patches.
- Add Reviewed-by: Théo Lebrun <theo.lebrun@bootlin.com> to all patches.
- Split chained assignment in macb_tx_lpi_set() (suggested by checkpatch).
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.
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. 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. Adds register offset definitions
GEM_RXLPI/RXLPITIME/TXLPI/TXLPITIME (0x270-0x27c).
2. TX LPI engine: Introduces GEM_TXLPIEN (NCR bit 19) and
MACB_CAPS_EEE alongside the implementation that uses them.
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 (IEEE 802.3az Tw_sys_tx).
3. ethtool EEE ops: get_eee/set_eee delegating to phylink for PHY
negotiation and timer management.
4. RP1 enablement: Set MACB_CAPS_EEE for the Raspberry Pi 5's RP1
southbridge (Cadence GEM_GXL rev 0x00070109 + BCM54213PE PHY).
5. EyeQ5 enablement: Set MACB_CAPS_EEE for the Mobileye EyeQ5 GEM
instance, verified with a hardware loopback by Théo Lebrun.
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 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
net: cadence: macb: enable EEE for Mobileye EyeQ5
drivers/net/ethernet/cadence/macb.h | 20 +++++
drivers/net/ethernet/cadence/macb_main.c | 133 ++++++++++++++++++++++++++++++-
2 files changed, 151 insertions(+), 2 deletions(-)
--
2.51.0