netdev - RE: [PATCH 5/5] net: dsa: ocelot: add hardware timestamping support for Felix

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Date:   Thu, 21 Nov 2019 03:29:35 +0000
From:   "Y.b. Lu" <yangbo.lu@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        "David S . Miller" <davem@...emloft.net>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: RE: [PATCH 5/5] net: dsa: ocelot: add hardware timestamping support
 for Felix

Hi Andrew,

> -----Original Message-----
> From: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org> On
> Behalf Of Andrew Lunn
> Sent: Thursday, November 21, 2019 10:56 AM
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: netdev@...r.kernel.org; Alexandre Belloni
> <alexandre.belloni@...tlin.com>; Microchip Linux Driver Support
> <UNGLinuxDriver@...rochip.com>; David S . Miller <davem@...emloft.net>;
> Vladimir Oltean <vladimir.oltean@....com>; Claudiu Manoil
> <claudiu.manoil@....com>; Vivien Didelot <vivien.didelot@...il.com>;
> Florian Fainelli <f.fainelli@...il.com>; Richard Cochran
> <richardcochran@...il.com>
> Subject: Re: [PATCH 5/5] net: dsa: ocelot: add hardware timestamping support
> for Felix
> 
> > +static irqreturn_t felix_irq_handler(int irq, void *data) {
> > +	struct ocelot *ocelot = (struct ocelot *)data;
> > +
> > +	/* The INTB interrupt is used for both PTP TX timestamp interrupt
> > +	 * and preemption status change interrupt on each port.
> > +	 *
> > +	 * - Get txtstamp if have
> > +	 * - TODO: handle preemption. Without handling it, driver may get
> > +	 *   interrupt storm.
> > +	 */
> 
> I assume there are no register bits to enable/disable these two interrupt
> sources?
> 
> What is preemption?

[Y.b. Lu] For PTP timestamp interrupt, there are not register bits to enable/disable interrupt source, and to clean interrupt status.
That's why use threaded handler with oneshot flag.
For preemption, it is a feature of TSN Qbu. I'm not familiar with it. The function hasn't been supported/enabled in driver.
It seems it has status bit to check, but has no bits to enable/disable interrupt source either.

Thanks.
> 
>      Andrew