[PATCH net-next v2 0/5] net: cadence: macb: add IEEE 802.3az EEE support

[PATCH net-next v2 0/5] net: cadence: macb: add IEEE 802.3az EEE support

[Nicolai Buchwitz]

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 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      |  21 ++++
 drivers/net/ethernet/cadence/macb_main.c | 135 ++++++++++++++++++++++-
 2 files changed, 155 insertions(+), 1 deletion(-)

-- 
2.51.0

[PATCH net-next v2 1/5] net: cadence: macb: add EEE register definitions and capability flag

[Nicolai Buchwitz]

Add register and bitfield definitions for the Cadence GEM MAC's
IEEE 802.3az Energy Efficient Ethernet (EEE) support:

- LPI statistics counter registers (GEM_RXLPI, GEM_RXLPITIME,
  GEM_TXLPI, GEM_TXLPITIME) at offsets 0x270-0x27c
- TX LPI enable bitfield (GEM_TXLPIEN) in the NCR register (bit 19),
  which directly asserts/deasserts LPI on the transmit path
- MACB_CAPS_EEE capability flag to gate EEE support per platform

These registers are present in all Cadence GEM revisions that support
EEE (verified on SAMA5D2, SAME70, PIC32CZ, and RP1 variants).

No functional change.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/cadence/macb.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 87414a2ddf6e..729751d424c2 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -170,6 +170,10 @@
 #define GEM_PCSANNPTX		0x021c /* PCS AN Next Page TX */
 #define GEM_PCSANNPLP		0x0220 /* PCS AN Next Page LP */
 #define GEM_PCSANEXTSTS		0x023c /* PCS AN Extended Status */
+#define GEM_RXLPI		0x0270 /* RX LPI Transitions */
+#define GEM_RXLPITIME		0x0274 /* RX LPI Time */
+#define GEM_TXLPI		0x0278 /* TX LPI Transitions */
+#define GEM_TXLPITIME		0x027c /* TX LPI Time */
 #define GEM_DCFG1		0x0280 /* Design Config 1 */
 #define GEM_DCFG2		0x0284 /* Design Config 2 */
 #define GEM_DCFG3		0x0288 /* Design Config 3 */
@@ -305,6 +309,8 @@
 #define MACB_IRXFCS_SIZE	1
 
 /* GEM specific NCR bitfields. */
+#define GEM_TXLPIEN_OFFSET		19
+#define GEM_TXLPIEN_SIZE		1
 #define GEM_ENABLE_HS_MAC_OFFSET	31
 #define GEM_ENABLE_HS_MAC_SIZE		1
 
@@ -779,6 +785,7 @@
 #define MACB_CAPS_DMA_PTP			BIT(22)
 #define MACB_CAPS_RSC				BIT(23)
 #define MACB_CAPS_NO_LSO			BIT(24)
+#define MACB_CAPS_EEE				BIT(25)
 
 /* LSO settings */
 #define MACB_LSO_UFO_ENABLE			0x01
-- 
2.51.0

[PATCH net-next v2 2/5] net: cadence: macb: add EEE LPI statistics counters

[Nicolai Buchwitz]

Expose the GEM MAC's EEE Low Power Idle hardware counters through
ethtool -S:

- rx_lpi_transitions: number of RX LPI entry events
- rx_lpi_time: cumulative time spent in RX LPI
- tx_lpi_transitions: number of TX LPI entry events (TXLPIEN 0->1)
- tx_lpi_time: cumulative time in TX LPI

These are clear-on-read hardware registers at offsets 0x270-0x27c,
automatically collected by the existing gem_statistics read loop.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/cadence/macb.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 729751d424c2..e3520e5aec67 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1050,6 +1050,10 @@ struct gem_stats {
 	u64	rx_ip_header_checksum_errors;
 	u64	rx_tcp_checksum_errors;
 	u64	rx_udp_checksum_errors;
+	u64	rx_lpi_transitions;
+	u64	rx_lpi_time;
+	u64	tx_lpi_transitions;
+	u64	tx_lpi_time;
 };
 
 /* Describes the name and offset of an individual statistic register, as
@@ -1149,6 +1153,10 @@ static const struct gem_statistic gem_statistics[] = {
 			    GEM_BIT(NDS_RXERR)),
 	GEM_STAT_TITLE_BITS(RXUDPCCNT, "rx_udp_checksum_errors",
 			    GEM_BIT(NDS_RXERR)),
+	GEM_STAT_TITLE(RXLPI, "rx_lpi_transitions"),
+	GEM_STAT_TITLE(RXLPITIME, "rx_lpi_time"),
+	GEM_STAT_TITLE(TXLPI, "tx_lpi_transitions"),
+	GEM_STAT_TITLE(TXLPITIME, "tx_lpi_time"),
 };
 
 #define GEM_STATS_LEN ARRAY_SIZE(gem_statistics)
-- 
2.51.0

[PATCH net-next v2 3/5] net: cadence: macb: implement EEE TX LPI support

[Nicolai Buchwitz]

Implement Energy Efficient Ethernet TX Low Power Idle using phylink's
managed EEE framework. The Cadence GEM MAC has no built-in idle timer
- TXLPIEN (NCR bit 19) immediately blocks all TX when set and the MAC
does NOT auto-wake - so the driver uses a software delayed_work timer
for idle detection.

The TX LPI lifecycle:
  - phylink calls mac_enable_tx_lpi() after link-up with the negotiated
    timer value. The driver defers the first LPI entry by 1 second per
    IEEE 802.3az section 22.7a.
  - macb_tx_complete() reschedules the idle timer after each TX drain.
  - macb_start_xmit() wakes from LPI by clearing TXLPIEN, cancelling
    the pending work, and waiting 50us (conservative Tw_sys) before
    initiating the transmit.
  - phylink calls mac_disable_tx_lpi() before link-down, which cancels
    the work and clears TXLPIEN.

The phylink_config is populated with LPI capabilities (MII, GMII, RGMII
modes; 100FD and 1000FD speeds) and a 250ms default idle timer, gated
on MACB_CAPS_EEE.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/cadence/macb.h      |   6 ++
 drivers/net/ethernet/cadence/macb_main.c | 110 +++++++++++++++++++++++
 2 files changed, 116 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index e3520e5aec67..a17e537cdeb6 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1372,6 +1372,12 @@ struct macb {
 
 	struct work_struct	hresp_err_bh_work;
 
+	/* EEE / LPI state */
+	bool			eee_active;
+	bool			tx_lpi_enabled;
+	struct delayed_work	tx_lpi_work;
+	u32			tx_lpi_timer;
+
 	int	rx_bd_rd_prefetch;
 	int	tx_bd_rd_prefetch;
 
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 43cd013bb70e..fb64a97725b1 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -10,6 +10,7 @@
 #include <linux/clk-provider.h>
 #include <linux/clk.h>
 #include <linux/crc32.h>
+#include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/etherdevice.h>
 #include <linux/firmware/xlnx-zynqmp.h>
@@ -589,6 +590,92 @@ static const struct phylink_pcs_ops macb_phylink_pcs_ops = {
 	.pcs_config = macb_pcs_config,
 };
 
+static void macb_tx_lpi_set(struct macb *bp, bool enable)
+{
+	unsigned long flags;
+	u32 ncr;
+
+	spin_lock_irqsave(&bp->lock, flags);
+	ncr = macb_readl(bp, NCR);
+	if (enable)
+		ncr |= GEM_BIT(TXLPIEN);
+	else
+		ncr &= ~GEM_BIT(TXLPIEN);
+	macb_writel(bp, NCR, ncr);
+	bp->tx_lpi_enabled = enable;
+	spin_unlock_irqrestore(&bp->lock, flags);
+}
+
+static bool macb_tx_all_queues_idle(struct macb *bp)
+{
+	unsigned int q;
+
+	for (q = 0; q < bp->num_queues; q++) {
+		struct macb_queue *queue = &bp->queues[q];
+
+		if (queue->tx_head != queue->tx_tail)
+			return false;
+	}
+	return true;
+}
+
+static void macb_tx_lpi_work_fn(struct work_struct *work)
+{
+	struct macb *bp = container_of(work, struct macb, tx_lpi_work.work);
+
+	if (bp->eee_active && macb_tx_all_queues_idle(bp))
+		macb_tx_lpi_set(bp, true);
+}
+
+static void macb_tx_lpi_schedule(struct macb *bp)
+{
+	if (bp->eee_active)
+		mod_delayed_work(system_wq, &bp->tx_lpi_work,
+				 usecs_to_jiffies(bp->tx_lpi_timer));
+}
+
+/* Wake from LPI before transmitting. The MAC must deassert TXLPIEN
+ * and wait for the PHY to exit LPI before any frame can be sent.
+ * IEEE 802.3az Tw_sys is ~17us for 1000BASE-T, ~30us for 100BASE-TX;
+ * we use a conservative 50us.
+ */
+static void macb_tx_lpi_wake(struct macb *bp)
+{
+	if (!bp->tx_lpi_enabled)
+		return;
+
+	macb_tx_lpi_set(bp, false);
+	cancel_delayed_work(&bp->tx_lpi_work);
+	udelay(50);
+}
+
+static void macb_mac_disable_tx_lpi(struct phylink_config *config)
+{
+	struct net_device *ndev = to_net_dev(config->dev);
+	struct macb *bp = netdev_priv(ndev);
+
+	bp->eee_active = false;
+	cancel_delayed_work_sync(&bp->tx_lpi_work);
+	macb_tx_lpi_set(bp, false);
+}
+
+static int macb_mac_enable_tx_lpi(struct phylink_config *config, u32 timer,
+				  bool tx_clk_stop)
+{
+	struct net_device *ndev = to_net_dev(config->dev);
+	struct macb *bp = netdev_priv(ndev);
+
+	bp->tx_lpi_timer = timer;
+	bp->eee_active = true;
+
+	/* Defer initial LPI entry by 1 second after link-up per
+	 * IEEE 802.3az section 22.7a.
+	 */
+	mod_delayed_work(system_wq, &bp->tx_lpi_work, msecs_to_jiffies(1000));
+
+	return 0;
+}
+
 static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 			    const struct phylink_link_state *state)
 {
@@ -753,6 +840,8 @@ static const struct phylink_mac_ops macb_phylink_ops = {
 	.mac_config = macb_mac_config,
 	.mac_link_down = macb_mac_link_down,
 	.mac_link_up = macb_mac_link_up,
+	.mac_disable_tx_lpi = macb_mac_disable_tx_lpi,
+	.mac_enable_tx_lpi = macb_mac_enable_tx_lpi,
 };
 
 static bool macb_phy_handle_exists(struct device_node *dn)
@@ -848,6 +937,18 @@ static int macb_mii_probe(struct net_device *dev)
 		}
 	}
 
+	/* Configure EEE LPI if supported */
+	if (bp->caps & MACB_CAPS_EEE) {
+		__set_bit(PHY_INTERFACE_MODE_MII,
+			  bp->phylink_config.lpi_interfaces);
+		__set_bit(PHY_INTERFACE_MODE_GMII,
+			  bp->phylink_config.lpi_interfaces);
+		phy_interface_set_rgmii(bp->phylink_config.lpi_interfaces);
+		bp->phylink_config.lpi_capabilities = MAC_100FD | MAC_1000FD;
+		bp->phylink_config.lpi_timer_default = 250000;
+		bp->phylink_config.eee_enabled_default = true;
+	}
+
 	bp->phylink = phylink_create(&bp->phylink_config, bp->pdev->dev.fwnode,
 				     bp->phy_interface, &macb_phylink_ops);
 	if (IS_ERR(bp->phylink)) {
@@ -1244,6 +1345,9 @@ static int macb_tx_complete(struct macb_queue *queue, int budget)
 		netif_wake_subqueue(bp->dev, queue_index);
 	spin_unlock_irqrestore(&queue->tx_ptr_lock, flags);
 
+	if (packets)
+		macb_tx_lpi_schedule(bp);
+
 	return packets;
 }
 
@@ -2349,6 +2453,8 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	netdev_tx_sent_queue(netdev_get_tx_queue(bp->dev, queue_index),
 			     skb->len);
 
+	macb_tx_lpi_wake(bp);
+
 	spin_lock(&bp->lock);
 	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
 	spin_unlock(&bp->lock);
@@ -3010,6 +3116,8 @@ static int macb_close(struct net_device *dev)
 		netdev_tx_reset_queue(netdev_get_tx_queue(dev, q));
 	}
 
+	cancel_delayed_work_sync(&bp->tx_lpi_work);
+
 	phylink_stop(bp->phylink);
 	phylink_disconnect_phy(bp->phylink);
 
@@ -5616,6 +5724,7 @@ static int macb_probe(struct platform_device *pdev)
 	}
 
 	INIT_WORK(&bp->hresp_err_bh_work, macb_hresp_error_task);
+	INIT_DELAYED_WORK(&bp->tx_lpi_work, macb_tx_lpi_work_fn);
 
 	netdev_info(dev, "Cadence %s rev 0x%08x at 0x%08lx irq %d (%pM)\n",
 		    macb_is_gem(bp) ? "GEM" : "MACB", macb_readl(bp, MID),
@@ -5659,6 +5768,7 @@ static void macb_remove(struct platform_device *pdev)
 		mdiobus_free(bp->mii_bus);
 
 		device_set_wakeup_enable(&bp->pdev->dev, 0);
+		cancel_delayed_work_sync(&bp->tx_lpi_work);
 		cancel_work_sync(&bp->hresp_err_bh_work);
 		pm_runtime_disable(&pdev->dev);
 		pm_runtime_dont_use_autosuspend(&pdev->dev);
-- 
2.51.0

[PATCH net-next v2 4/5] net: cadence: macb: add ethtool EEE support

[Nicolai Buchwitz]

Implement ethtool get_eee and set_eee operations for the Cadence GEM
MAC, delegating to phylink for PHY-level EEE negotiation state.

The MAC-level LPI control (TXLPIEN) is not manipulated directly in the
ethtool ops - phylink manages the full EEE lifecycle through the
mac_enable_tx_lpi / mac_disable_tx_lpi callbacks.

Both ops are gated on MACB_CAPS_EEE; platforms without the capability
flag return -EOPNOTSUPP.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/cadence/macb_main.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index fb64a97725b1..87097100b88c 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4032,6 +4032,26 @@ static const struct ethtool_ops macb_ethtool_ops = {
 	.set_ringparam		= macb_set_ringparam,
 };
 
+static int macb_get_eee(struct net_device *dev, struct ethtool_keee *eee)
+{
+	struct macb *bp = netdev_priv(dev);
+
+	if (!(bp->caps & MACB_CAPS_EEE))
+		return -EOPNOTSUPP;
+
+	return phylink_ethtool_get_eee(bp->phylink, eee);
+}
+
+static int macb_set_eee(struct net_device *dev, struct ethtool_keee *eee)
+{
+	struct macb *bp = netdev_priv(dev);
+
+	if (!(bp->caps & MACB_CAPS_EEE))
+		return -EOPNOTSUPP;
+
+	return phylink_ethtool_set_eee(bp->phylink, eee);
+}
+
 static const struct ethtool_ops gem_ethtool_ops = {
 	.get_regs_len		= macb_get_regs_len,
 	.get_regs		= macb_get_regs,
@@ -4053,6 +4073,8 @@ static const struct ethtool_ops gem_ethtool_ops = {
 	.get_rxnfc			= gem_get_rxnfc,
 	.set_rxnfc			= gem_set_rxnfc,
 	.get_rx_ring_count		= gem_get_rx_ring_count,
+	.get_eee		= macb_get_eee,
+	.set_eee		= macb_set_eee,
 };
 
 static int macb_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
-- 
2.51.0

[PATCH net-next v2 5/5] net: cadence: macb: enable EEE for Raspberry Pi RP1

[Nicolai Buchwitz]

Enable IEEE 802.3az Energy Efficient Ethernet on the Raspberry Pi 5's
RP1 southbridge by adding MACB_CAPS_EEE to its platform config.

The RP1 contains a Cadence GEM_GXL MAC (revision 0x00070109) paired
with a Broadcom BCM54213PE PHY, both of which support EEE at
1000BASE-T and 100BASE-TX.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/cadence/macb_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 87097100b88c..2bf27a266e16 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -5516,7 +5516,8 @@ static const struct macb_config eyeq5_config = {
 static const struct macb_config raspberrypi_rp1_config = {
 	.caps = MACB_CAPS_GIGABIT_MODE_AVAILABLE | MACB_CAPS_CLK_HW_CHG |
 		MACB_CAPS_JUMBO |
-		MACB_CAPS_GEM_HAS_PTP,
+		MACB_CAPS_GEM_HAS_PTP |
+		MACB_CAPS_EEE,
 	.dma_burst_length = 16,
 	.clk_init = macb_clk_init,
 	.init = macb_init,
-- 
2.51.0

Re: [PATCH net-next v2 3/5] net: cadence: macb: implement EEE TX LPI support

[Russell King (Oracle)]

On Tue, Feb 24, 2026 at 10:18:19AM +0100, Nicolai Buchwitz wrote:
> Implement Energy Efficient Ethernet TX Low Power Idle using phylink's
> managed EEE framework. The Cadence GEM MAC has no built-in idle timer
> - TXLPIEN (NCR bit 19) immediately blocks all TX when set and the MAC
> does NOT auto-wake - so the driver uses a software delayed_work timer
> for idle detection.
> 
> The TX LPI lifecycle:
>   - phylink calls mac_enable_tx_lpi() after link-up with the negotiated
>     timer value. The driver defers the first LPI entry by 1 second per
>     IEEE 802.3az section 22.7a.
>   - macb_tx_complete() reschedules the idle timer after each TX drain.
>   - macb_start_xmit() wakes from LPI by clearing TXLPIEN, cancelling
>     the pending work, and waiting 50us (conservative Tw_sys) before
>     initiating the transmit.
>   - phylink calls mac_disable_tx_lpi() before link-down, which cancels
>     the work and clears TXLPIEN.
> 
> The phylink_config is populated with LPI capabilities (MII, GMII, RGMII
> modes; 100FD and 1000FD speeds) and a 250ms default idle timer, gated
> on MACB_CAPS_EEE.

Much better, thanks. One suggestion:

> +static void macb_tx_lpi_set(struct macb *bp, bool enable)

bool return type.

> +{
> +	unsigned long flags;
> +	u32 ncr;

	u32 old, ncr;

> +
> +	spin_lock_irqsave(&bp->lock, flags);
> +	ncr = macb_readl(bp, NCR);

	old = ncr;

> +	if (enable)
> +		ncr |= GEM_BIT(TXLPIEN);
> +	else
> +		ncr &= ~GEM_BIT(TXLPIEN);

	if (old != ncr)
> +	macb_writel(bp, NCR, ncr);
> +	bp->tx_lpi_enabled = enable;

No need for tx_lpi_enabled

> +	spin_unlock_irqrestore(&bp->lock, flags);

	return old != ncr;

> +}

...

> +/* Wake from LPI before transmitting. The MAC must deassert TXLPIEN
> + * and wait for the PHY to exit LPI before any frame can be sent.
> + * IEEE 802.3az Tw_sys is ~17us for 1000BASE-T, ~30us for 100BASE-TX;
> + * we use a conservative 50us.
> + */
> +static void macb_tx_lpi_wake(struct macb *bp)
> +{
> +	if (!bp->tx_lpi_enabled)
> +		return;

No need for this if().

> +
> +	macb_tx_lpi_set(bp, false);

instead:
	if (!macb_tx_lpi_set(bp, false))
		return;

The presence of the spinlock in macb_tx_lpi_set() suggests that there
could be races, so keeping the state completely inside the spinlock
region would be sensible.

> +	cancel_delayed_work(&bp->tx_lpi_work);

I wonder whether this is reliable on its own. cancel_delayed_work()
documentation says:

 * Note:
 * The work callback function may still be running on return, unless
 * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
 * use cancel_delayed_work_sync() to wait on it.

That means macb_tx_lpi_work_fn() could have just been entered at the
point that cancel_delayed_work() has been called. Would that cause a
problem, e.g. setting LPI mode again, or would we be guaranteed that
macb_tx_all_queues_idle() returns false preventing LPI mode being set
again?

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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Re: [PATCH net-next v2 3/5] net: cadence: macb: implement EEE TX LPI support

[Nicolai Buchwitz]

On 24.2.2026 11:17, Russell King (Oracle) wrote:
> On Tue, Feb 24, 2026 at 10:18:19AM +0100, Nicolai Buchwitz wrote:
>> Implement Energy Efficient Ethernet TX Low Power Idle using phylink's
>> managed EEE framework. The Cadence GEM MAC has no built-in idle timer
>> - TXLPIEN (NCR bit 19) immediately blocks all TX when set and the MAC
>> does NOT auto-wake - so the driver uses a software delayed_work timer
>> for idle detection.
>> 
>> The TX LPI lifecycle:
>>   - phylink calls mac_enable_tx_lpi() after link-up with the 
>> negotiated
>>     timer value. The driver defers the first LPI entry by 1 second per
>>     IEEE 802.3az section 22.7a.
>>   - macb_tx_complete() reschedules the idle timer after each TX drain.
>>   - macb_start_xmit() wakes from LPI by clearing TXLPIEN, cancelling
>>     the pending work, and waiting 50us (conservative Tw_sys) before
>>     initiating the transmit.
>>   - phylink calls mac_disable_tx_lpi() before link-down, which cancels
>>     the work and clears TXLPIEN.
>> 
>> The phylink_config is populated with LPI capabilities (MII, GMII, 
>> RGMII
>> modes; 100FD and 1000FD speeds) and a 250ms default idle timer, gated
>> on MACB_CAPS_EEE.
> 
> Much better, thanks. One suggestion:

Thanks for the quick feedback! I will address this in a v3 of this 
series.

> 
>> +static void macb_tx_lpi_set(struct macb *bp, bool enable)
> 
> bool return type.
> 
>> +{
>> +	unsigned long flags;
>> +	u32 ncr;
> 
> 	u32 old, ncr;
> 
>> +
>> +	spin_lock_irqsave(&bp->lock, flags);
>> +	ncr = macb_readl(bp, NCR);
> 
> 	old = ncr;
> 
>> +	if (enable)
>> +		ncr |= GEM_BIT(TXLPIEN);
>> +	else
>> +		ncr &= ~GEM_BIT(TXLPIEN);
> 
> 	if (old != ncr)
>> +	macb_writel(bp, NCR, ncr);
>> +	bp->tx_lpi_enabled = enable;
> 
> No need for tx_lpi_enabled
> 
>> +	spin_unlock_irqrestore(&bp->lock, flags);
> 
> 	return old != ncr;
> 
>> +}
> 
> ...
> 
>> +/* Wake from LPI before transmitting. The MAC must deassert TXLPIEN
>> + * and wait for the PHY to exit LPI before any frame can be sent.
>> + * IEEE 802.3az Tw_sys is ~17us for 1000BASE-T, ~30us for 100BASE-TX;
>> + * we use a conservative 50us.
>> + */
>> +static void macb_tx_lpi_wake(struct macb *bp)
>> +{
>> +	if (!bp->tx_lpi_enabled)
>> +		return;
> 
> No need for this if().
> 
>> +
>> +	macb_tx_lpi_set(bp, false);
> 
> instead:
> 	if (!macb_tx_lpi_set(bp, false))
> 		return;
> 
> The presence of the spinlock in macb_tx_lpi_set() suggests that there
> could be races, so keeping the state completely inside the spinlock
> region would be sensible.
> 
>> +	cancel_delayed_work(&bp->tx_lpi_work);
> 
> I wonder whether this is reliable on its own. cancel_delayed_work()
> documentation says:
> 
>  * Note:
>  * The work callback function may still be running on return, unless
>  * it returns %true and the work doesn't re-arm itself.  Explicitly 
> flush or
>  * use cancel_delayed_work_sync() to wait on it.
> 
> That means macb_tx_lpi_work_fn() could have just been entered at the
> point that cancel_delayed_work() has been called. Would that cause a
> problem, e.g. setting LPI mode again, or would we be guaranteed that
> macb_tx_all_queues_idle() returns false preventing LPI mode being set
> again?

AFAIK, the race shouldn't be an issue here because macb_tx_lpi_wake()
is called from macb_start_xmit() after the TX descriptors have been
written and tx_head has been advanced (there's a wmb() before the
call to ensure visibility). So if macb_tx_lpi_work_fn() happens to
be running concurrently, macb_tx_all_queues_idle() will see
tx_head != tx_tail and return false, preventing LPI from being
re-enabled.

> 
> Thanks.

Nicolai