net: cadence: macb: implement EEE TX LPI support

The GEM MAC has hardware LPI registers (NCR bit 19: TXLPIEN) but no
built-in idle timer, so asserting TXLPIEN blocks all TX immediately
with no automatic wake. A software idle timer is required, as noted
in Microchip documentation (section 40.6.19): "It is best to use
firmware to control LPI."

Implement phylink managed EEE using the mac_enable_tx_lpi and
mac_disable_tx_lpi callbacks:

- macb_tx_lpi_set(): sets or clears TXLPIEN; requires bp->lock to be
  held by the caller (asserted with lockdep_assert_held). Returns bool
  indicating whether the register actually changed, avoiding redundant
  writes and unnecessary udelay on the xmit fast path.

- macb_tx_lpi_work_fn(): delayed_work handler that enters LPI if all
  TX queues are idle and EEE is still active. Takes bp->lock with
  irqsave before calling macb_tx_lpi_set().

- macb_tx_lpi_schedule(): arms the work timer using the LPI timer
  value provided by phylink (default 250 ms). Called from
  macb_tx_complete() after each TX drain so the idle countdown
  restarts whenever the ring goes quiet.

- macb_tx_lpi_wake(): called from macb_start_xmit() under bp->lock,
  immediately before TSTART. Returns early if eee_active is false to
  avoid a register read on the common path when EEE is disabled.
  Clears TXLPIEN and applies a 50 us udelay for PHY wake (IEEE
  802.3az Tw_sys_tx is 16.5 us for 1000BASE-T / 30 us for
  100BASE-TX; GEM has no hardware enforcement). Only delays when
  TXLPIEN was actually set. The delay is placed after tx_head is
  advanced so the work_fn's queue-idle check sees a non-empty ring
  and cannot race back into LPI before the frame is transmitted.

- mac_enable_tx_lpi: stores the timer and sets eee_active under
  bp->lock, then defers the first LPI entry by 1 second per IEEE
  802.3az section 22.7a.

- mac_disable_tx_lpi: cancels the work (sync, without the lock to
  avoid deadlock with the work_fn), then takes bp->lock to clear
  eee_active and deassert TXLPIEN.

Populate phylink_config lpi_interfaces (MII, GMII, RGMII variants)
and lpi_capabilities (MAC_100FD | MAC_1000FD) so phylink can
negotiate EEE with the PHY and call the callbacks appropriately.
Set lpi_timer_default to 250000 us and eee_enabled_default to true.

Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Reviewed-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Link: https://patch.msgid.link/20260304105432.631186-3-nb@tipi-net.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 19aa98d01c8ccd302f54d0795b7b3582a1d35fa4..c69828b27dae6b7a9d6c299204b22ce1ef4a5e65 100644 (file)
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -309,6 +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
 
@@ -783,6 +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
@@ -1369,6 +1372,11 @@ struct macb {
 
        struct work_struct      hresp_err_bh_work;
 
+       /* EEE / LPI state */
+       bool                    eee_active;
+       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 17f0ad3d7a0924a7dc2fc0a13505aff7d2499ffa..4e776c67f408f0012f03787e5537a1eda8747310 100644 (file)
--- 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>
@@ -621,6 +622,107 @@ static const struct phylink_pcs_ops macb_phylink_pcs_ops = {
        .pcs_config = macb_pcs_config,
 };
 
+static bool macb_tx_lpi_set(struct macb *bp, bool enable)
+{
+       u32 old, ncr;
+
+       lockdep_assert_held(&bp->lock);
+
+       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);
+
+       return old != ncr;
+}
+
+static bool macb_tx_all_queues_idle(struct macb *bp)
+{
+       struct macb_queue *queue;
+       unsigned int q;
+
+       for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
+               if (READ_ONCE(queue->tx_head) != READ_ONCE(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);
+       unsigned long flags;
+
+       spin_lock_irqsave(&bp->lock, flags);
+       if (bp->eee_active && macb_tx_all_queues_idle(bp))
+               macb_tx_lpi_set(bp, true);
+       spin_unlock_irqrestore(&bp->lock, flags);
+}
+
+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)
+{
+       lockdep_assert_held(&bp->lock);
+
+       if (!bp->eee_active)
+               return;
+
+       if (!macb_tx_lpi_set(bp, false))
+               return;
+
+       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);
+       unsigned long flags;
+
+       cancel_delayed_work_sync(&bp->tx_lpi_work);
+
+       spin_lock_irqsave(&bp->lock, flags);
+       bp->eee_active = false;
+       macb_tx_lpi_set(bp, false);
+       spin_unlock_irqrestore(&bp->lock, flags);
+}
+
+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);
+       unsigned long flags;
+
+       spin_lock_irqsave(&bp->lock, flags);
+       bp->tx_lpi_timer = timer;
+       bp->eee_active = true;
+       spin_unlock_irqrestore(&bp->lock, flags);
+
+       /* 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)
 {
@@ -769,6 +871,8 @@ 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)
@@ -864,6 +968,18 @@ 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)) {
@@ -1260,6 +1376,9 @@ 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;
 }
 
@@ -2366,6 +2485,7 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
                             skb->len);
 
        spin_lock(&bp->lock);
+       macb_tx_lpi_wake(bp);
        macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
        spin_unlock(&bp->lock);
 
@@ -3026,6 +3146,8 @@ 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);
 
@@ -5629,6 +5751,7 @@ 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),
@@ -5672,6 +5795,7 @@ 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);