netdev - Re: [PATCH net-next v3 1/1] net: stmmac: Add support for external trigger timestamping

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Message-ID: <20210411151055.GA5719@hoboy.vegasvil.org>
Date:   Sun, 11 Apr 2021 08:10:55 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Wong Vee Khee <vee.khee.wong@...ux.intel.com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 1/1] net: stmmac: Add support for external
 trigger timestamping

On Sun, Apr 11, 2021 at 10:40:28AM +0800, Wong Vee Khee wrote:
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> index 60566598d644..60e17fd24aba 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> @@ -296,6 +296,13 @@ static int intel_crosststamp(ktime_t *device,
>  
>  	intel_priv = priv->plat->bsp_priv;
>  
> +	/* Both internal crosstimestamping and external triggered event
> +	 * timestamping cannot be run concurrently.
> +	 */
> +	if (priv->plat->ext_snapshot_en)
> +		return -EBUSY;
> +
> +	mutex_lock(&priv->aux_ts_lock);

Lock, then ...

>  	/* Enable Internal snapshot trigger */
>  	acr_value = readl(ptpaddr + PTP_ACR);
>  	acr_value &= ~PTP_ACR_MASK;
> @@ -321,6 +328,7 @@ static int intel_crosststamp(ktime_t *device,
>  	acr_value = readl(ptpaddr + PTP_ACR);
>  	acr_value |= PTP_ACR_ATSFC;
>  	writel(acr_value, ptpaddr + PTP_ACR);
> +	mutex_unlock(&priv->aux_ts_lock);

unlock, then ...
  
>  	/* Trigger Internal snapshot signal
>  	 * Create a rising edge by just toggle the GPO1 to low
> @@ -355,6 +363,8 @@ static int intel_crosststamp(ktime_t *device,
>  		*system = convert_art_to_tsc(art_time);
>  	}
>  
> +	/* Release the mutex */
> +	mutex_unlock(&priv->aux_ts_lock);

unlock again?  Huh?

> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index c49debb62b05..abadcd8cdc41 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -239,6 +239,9 @@ struct stmmac_priv {
>  	int use_riwt;
>  	int irq_wake;
>  	spinlock_t ptp_lock;
> +	/* Mutex lock for Auxiliary Snapshots */
> +	struct mutex aux_ts_lock;

In the comment, please be specific about which data are protected.
For example:

	/* Protects auxiliary snapshot registers from concurrent access. */

> @@ -163,6 +166,43 @@ static void get_ptptime(void __iomem *ptpaddr, u64 *ptp_time)
>  	*ptp_time = ns;
>  }
>  
> +static void timestamp_interrupt(struct stmmac_priv *priv)
> +{
> +	struct ptp_clock_event event;
> +	unsigned long flags;
> +	u32 num_snapshot;
> +	u32 ts_status;
> +	u32 tsync_int;

Please group same types together (u32) in a one-line list.

> +	u64 ptp_time;
> +	int i;
> +
> +	tsync_int = readl(priv->ioaddr + GMAC_INT_STATUS) & GMAC_INT_TSIE;
> +
> +	if (!tsync_int)
> +		return;
> +
> +	/* Read timestamp status to clear interrupt from either external
> +	 * timestamp or start/end of PPS.
> +	 */
> +	ts_status = readl(priv->ioaddr + GMAC_TIMESTAMP_STATUS);

Reading this register has a side effect of clearing status?  If so,
doesn't it need protection against concurrent access?

The function, intel_crosststamp() also reads this bit.

> +	if (!priv->plat->ext_snapshot_en)
> +		return;

Doesn't this test come too late?  Setting ts_status just cleared the
bit used by the other code path.

> +	num_snapshot = (ts_status & GMAC_TIMESTAMP_ATSNS_MASK) >>
> +		       GMAC_TIMESTAMP_ATSNS_SHIFT;
> +
> +	for (i = 0; i < num_snapshot; i++) {
> +		spin_lock_irqsave(&priv->ptp_lock, flags);
> +		get_ptptime(priv->ptpaddr, &ptp_time);
> +		spin_unlock_irqrestore(&priv->ptp_lock, flags);
> +		event.type = PTP_CLOCK_EXTTS;
> +		event.index = 0;
> +		event.timestamp = ptp_time;
> +		ptp_clock_event(priv->ptp_clock, &event);
> +	}
> +}
> +

> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
> index b164ae22e35f..d668c33a0746 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
> @@ -135,9 +135,13 @@ static int stmmac_enable(struct ptp_clock_info *ptp,
>  {
>  	struct stmmac_priv *priv =
>  	    container_of(ptp, struct stmmac_priv, ptp_clock_ops);
> +	void __iomem *ptpaddr = priv->ptpaddr;
> +	void __iomem *ioaddr = priv->hw->pcsr;
>  	struct stmmac_pps_cfg *cfg;
>  	int ret = -EOPNOTSUPP;
>  	unsigned long flags;
> +	u32 intr_value;
> +	u32 acr_value;

Please group same types together.

Thanks,
Richard