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

From: Wong Vee Khee <vee.khee.wong@linux.intel.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S . Miller" <davem@davemloft.net>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Voon Weifeng <weifeng.voon@intel.com>,
	Ong Boon Leong <boon.leong.ong@intel.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	Richard Cochran <richardcochran@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next v2 1/1] net: stmmac: Add support for external trigger timestamping
Date: Sat, 10 Apr 2021 21:16:09 +0800	[thread overview]
Message-ID: <20210410131609.GA12931@linux.intel.com> (raw)
In-Reply-To: <20210409175004.2fceacdd@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

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.