[PATCH net-next v2] net: stmmac: dwxgmac2: add XGMAC timestamp interrupt support

[Zxyan Zhu <zxyan0222@gmail.com>]

DWXGMAC2 uses XGMAC_TIMESTAMP_STATUS at offset 0xd20, while the
generic stmmac PTP handler reads the dwmac4 offset GMAC_TIMESTAMP_STATUS
(0xb20).  Before this change, the DWXGMAC2 and DWXLGMAC2 hwif entries
used &stmmac_ptp, whose timestamp_interrupt callback read the wrong
register and whose config_hw_tstamping callback never enabled the
XGMAC timestamp interrupt (XGMAC_TSIE was not in XGMAC_INT_DEFAULT_EN).
As a result, auxiliary snapshot events were never reported on XGMAC
platforms.

Add a dedicated DWXGMAC2 timestamp interrupt handler that:
- reads XGMAC_TIMESTAMP_STATUS before checking
  STMMAC_FLAG_EXT_SNAPSHOT_EN, so that the timestamp interrupt status is
  cleared even when auxiliary snapshots are disabled
- derives the pending auxiliary snapshot count from the persistent
  ATSNS field instead of the transient AUXTSTRIG status bit
- generates the corresponding PTP_CLOCK_EXTTS events

Also enable XGMAC_TSIE in XGMAC_INT_DEFAULT_EN and hook the new
handler into the DWXGMAC2 and DWXLGMAC2 hwif entries.

Signed-off-by: Zxyan Zhu <zxyan0222@gmail.com>
---
v1: https://lore.kernel.org/netdev/20260806-dwxgmac2-timestamp-irq-v1-1-c051c79c9d90@gmail.com/
v2:
- reads XGMAC_TIMESTAMP_STATUS before checking
  STMMAC_FLAG_EXT_SNAPSHOT_EN, so that the timestamp interrupt status is
  cleared even when auxiliary snapshots are disabled.
- Drop the unnecessary (u64) cast in dwxgmac2_get_mac_tx_timestamp().
- Reword the changelog to describe the real problem: the generic handler
  read the wrong register offset (0xb20 vs 0xd20) and the interrupt was
  never enabled, so auxiliary snapshot reporting never worked on XGMAC.
- Update the comment to clarify that TXTSC is cleared by
  XGMAC_TXTIMESTAMP_SEC, not by XGMAC_TIMESTAMP_STATUS.
---
 .../net/ethernet/stmicro/stmmac/dwxgmac2.h    |  2 +-
 .../ethernet/stmicro/stmmac/dwxgmac2_core.c   | 43 +++++++++++++++++++
 drivers/net/ethernet/stmicro/stmmac/hwif.c    |  4 +-
 drivers/net/ethernet/stmicro/stmmac/hwif.h    |  1 +
 .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 12 ++++++
 .../net/ethernet/stmicro/stmmac/stmmac_ptp.h  |  1 +
 6 files changed, 60 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
index 61b6d45a02f5..76e2860a9517 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
@@ -87,7 +87,7 @@
 #define XGMAC_TSIE			BIT(12)
 #define XGMAC_LPIIE			BIT(5)
 #define XGMAC_PMTIE			BIT(4)
-#define XGMAC_INT_DEFAULT_EN		(XGMAC_LPIIE | XGMAC_PMTIE)
+#define XGMAC_INT_DEFAULT_EN		(XGMAC_LPIIE | XGMAC_PMTIE | XGMAC_TSIE)
 #define XGMAC_Qx_TX_FLOW_CTRL(x)	(0x00000070 + (x) * 4)
 #define XGMAC_PT			GENMASK(31, 16)
 #define XGMAC_TFE			BIT(1)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
index f02b434bbd50..b849cebf9b29 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
@@ -1154,6 +1154,49 @@ static int dwxgmac2_get_mac_tx_timestamp(struct mac_device_info *hw, u64 *ts)
 	return 0;
 }
 
+void dwxgmac2_timestamp_interrupt(struct stmmac_priv *priv)
+{
+	u32 ts_status, pending_snapshots, acr_value, channel;
+	struct ptp_clock_event event;
+	unsigned long flags;
+	u64 ptp_time;
+	int i;
+
+	/* Read XGMAC_TIMESTAMP_STATUS to get the AUX snapshot
+	 * count.  This read also clears the TSIS bit in
+	 * XGMAC_INT_STATUS.
+	 * TX timestamp polling may have already cleared TSIS
+	 * and AUXTSTRIG, so rely on ATSNS instead.
+	 * TXTSC is cleared by XGMAC_TXTIMESTAMP_SEC, not by
+	 * this register, so there is no conflict.
+	 */
+	ts_status = readl(priv->ioaddr + XGMAC_TIMESTAMP_STATUS);
+
+	if (!(priv->plat->flags & STMMAC_FLAG_EXT_SNAPSHOT_EN))
+		return;
+
+	pending_snapshots = FIELD_GET(XGMAC_TIMESTAMP_ATSNS_MASK, ts_status);
+	if (!pending_snapshots)
+		return;
+
+	acr_value = readl(priv->ptpaddr + PTP_ACR);
+	channel = FIELD_GET(PTP_ACR_MASK, acr_value);
+	if (!channel)
+		return;
+	channel = ilog2(channel);
+
+	for (i = 0; i < pending_snapshots; i++) {
+		read_lock_irqsave(&priv->ptp_lock, flags);
+		stmmac_get_ptptime(priv, priv->ptpaddr, &ptp_time);
+		read_unlock_irqrestore(&priv->ptp_lock, flags);
+
+		event.type = PTP_CLOCK_EXTTS;
+		event.index = channel;
+		event.timestamp = ptp_time;
+		ptp_clock_event(priv->ptp_clock, &event);
+	}
+}
+
 static int dwxgmac2_flex_pps_config(void __iomem *ioaddr, int index,
 				    struct stmmac_pps_cfg *cfg, bool enable,
 				    u32 sub_second_inc, u32 systime_flags)
diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.c b/drivers/net/ethernet/stmicro/stmmac/hwif.c
index 511b0fd5e834..9718582b8480 100644
--- a/drivers/net/ethernet/stmicro/stmmac/hwif.c
+++ b/drivers/net/ethernet/stmicro/stmmac/hwif.c
@@ -258,7 +258,7 @@ static const struct stmmac_hwif_entry {
 		.dma = &dwxgmac210_dma_ops,
 		.mac = &dwxgmac210_ops,
 		.vlan = &dwxgmac210_vlan_ops,
-		.hwtimestamp = &stmmac_ptp,
+		.hwtimestamp = &dwxgmac2_ptp,
 		.ptp = &stmmac_ptp_clock_ops,
 		.mode = NULL,
 		.tc = &dwmac510_tc_ops,
@@ -280,7 +280,7 @@ static const struct stmmac_hwif_entry {
 		.dma = &dwxgmac210_dma_ops,
 		.mac = &dwxlgmac2_ops,
 		.vlan = &dwxlgmac2_vlan_ops,
-		.hwtimestamp = &stmmac_ptp,
+		.hwtimestamp = &dwxgmac2_ptp,
 		.ptp = &stmmac_ptp_clock_ops,
 		.mode = NULL,
 		.tc = &dwmac510_tc_ops,
diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h b/drivers/net/ethernet/stmicro/stmmac/hwif.h
index e6317b94fff7..818ab3daa91c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/hwif.h
+++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h
@@ -671,6 +671,7 @@ extern const struct stmmac_desc_ops ndesc_ops;
 
 extern const struct stmmac_hwtimestamp stmmac_ptp;
 extern const struct stmmac_hwtimestamp dwmac1000_ptp;
+extern const struct stmmac_hwtimestamp dwxgmac2_ptp;
 
 extern const struct stmmac_mode_ops ring_mode_ops;
 extern const struct stmmac_mode_ops chain_mode_ops;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index b9a985fa772c..9d7d24259abd 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -277,3 +277,15 @@ const struct stmmac_hwtimestamp dwmac1000_ptp = {
 	.get_ptptime = dwmac1000_get_ptptime,
 	.timestamp_interrupt = dwmac1000_timestamp_interrupt,
 };
+
+const struct stmmac_hwtimestamp dwxgmac2_ptp = {
+	.config_hw_tstamping = config_hw_tstamping,
+	.init_systime = init_systime,
+	.config_sub_second_increment = config_sub_second_increment,
+	.config_addend = config_addend,
+	.adjust_systime = adjust_systime,
+	.get_systime = get_systime,
+	.get_ptptime = get_ptptime,
+	.timestamp_interrupt = dwxgmac2_timestamp_interrupt,
+	.hwtstamp_correct_latency = hwtstamp_correct_latency,
+};
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
index 3fe0e3a80e80..dade09614163 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
@@ -103,6 +103,7 @@ int dwmac1000_ptp_enable(struct ptp_clock_info *ptp,
 
 void dwmac1000_get_ptptime(void __iomem *ptpaddr, u64 *ptp_time);
 void dwmac1000_timestamp_interrupt(struct stmmac_priv *priv);
+void dwxgmac2_timestamp_interrupt(struct stmmac_priv *priv);
 
 extern const struct ptp_clock_info stmmac_ptp_clock_ops;
 extern const struct ptp_clock_info dwmac1000_ptp_clock_ops;
-- 
2.34.1