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

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

On 8/10/26 12:02, Zxyan Zhu wrote:
> 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>

If there's an interrupt storm, then this should probably be a fix for -net
with a Fixes tag.

Maxime

> ---
> 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;