linux-kernel - Re: [PATCH net-next v2 1/1] net: stmmac: Add support for external trigger timestamping

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Date:   Sat, 10 Apr 2021 21:16:09 +0800
From:   Wong Vee Khee <vee.khee.wong@...ux.intel.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        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,
        Richard Cochran <richardcochran@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/1] net: stmmac: Add support for external
 trigger timestamping

On Fri, Apr 09, 2021 at 05:50:04PM -0700, Jakub Kicinski wrote:
> Other than the minor nit below LGTM. Let's give Richard one more day.
> 
> On Thu,  8 Apr 2021 01:04:42 +0800 Wong Vee Khee wrote:
> > +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;
> > +	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);
> > +
> > +	if (priv->plat->ext_snapshot_en) {
> 
> Are you intending to add more code after this if? Otherwise you could
> flip the condition and return early instead of having the extra level
> of indentation.
>

Thanks fo the suggestion.
There's no plan to add more code after this as per STMMAC features that
required this interrupt. I will flip the condition.

> > +		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);
> > +		}
> > +	}
> > +}
> 
> Not really related to this patch but how does stmmac set IRQF_SHARED
> and yet not track if it indeed generated the interrupt? Isn't that
> against the rules?
>

Good point! Thanks for pointing that out. I looked at how STMMAC
interrupt handlers are coded, and indeed there are no tracking. Will
work on that and send as a seperate patch in near future.