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From: Kurt Kanzenbach <kurt@linutronix.de>
To: Vinicius Costa Gomes <vinicius.gomes@intel.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Richard Cochran <richardcochran@gmail.com>,
	Kamil Alkhouri <kamil.alkhouri@hs-offenburg.de>,
	ilias.apalodimas@linaro.org, Vladimir Oltean <olteanv@gmail.com>
Subject: Re: [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support
Date: Tue, 25 Aug 2020 11:23:56 +0200	[thread overview]
Message-ID: <87bliz13kj.fsf@kurt> (raw)
In-Reply-To: <87pn7ftx6b.fsf@intel.com>

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On Mon Aug 24 2020, Vinicius Costa Gomes wrote:
> Hi,
>
> Kurt Kanzenbach <kurt@linutronix.de> writes:
>
[snip]
>> +	/* Setup timer for schedule switch: The IP core only allows to set a
>> +	 * cycle start timer 8 seconds in the future. This is why we setup the
>> +	 * hritmer to base_time - 5 seconds. Then, we have enough time to
>> +	 * activate IP core's EST timer.
>> +	 */
>> +	start = ktime_sub_ns(schedule->base_time, (u64)5 * NSEC_PER_SEC);
>> +	hrtimer_start_range_ns(&hellcreek_port->cycle_start_timer, start,
>> +			       NSEC_PER_SEC, HRTIMER_MODE_ABS);
>
> If we are talking about seconds here, I don't think you need to use a
> hrtimer, you could use a workqueue/delayed_work. Should make things a
> bit simpler.

I've used hrtimers for one reason: The hrtimer provides a way to fire at
an absolute base time based on CLOCK_TAI. All the other facilities such
as workqueues, timer list timers, etc do not.

In the typical setup, we run ptp4l as boundary clock (or as TAB which is
work in progress) and phc2sys to synchronize the ptp clock to the Linux
system. Let's assume we setup a TAPRIO schedule with a base time X. Now,
the grand master time changes meaning the timer has to go off earlier or
later.

Thanks,
Kurt

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  reply	other threads:[~2020-08-25  9:24 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-20  8:11 [PATCH v3 0/8] Hirschmann Hellcreek DSA driver Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 1/8] net: dsa: Add tag handling for Hirschmann Hellcreek switches Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 2/8] net: dsa: Add DSA driver " Kurt Kanzenbach
2020-08-24 22:44   ` Andrew Lunn
2020-08-25  9:07     ` Kurt Kanzenbach
2020-08-25 13:56       ` Andrew Lunn
2020-08-25 14:48         ` Kurt Kanzenbach
2020-08-27 10:29           ` Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 3/8] net: dsa: hellcreek: Add PTP clock support Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 4/8] net: dsa: hellcreek: Add support for hardware timestamping Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support Kurt Kanzenbach
2020-08-22 14:39   ` Vladimir Oltean
2020-08-24  6:10     ` Kurt Kanzenbach
2020-08-24 23:45       ` Vinicius Costa Gomes
2020-08-25  9:42         ` Kurt Kanzenbach
2020-08-25 17:58           ` Vinicius Costa Gomes
2020-08-27 10:12             ` Kurt Kanzenbach
2020-08-25  9:46         ` Vladimir Oltean
2020-08-25 10:09           ` Kurt Kanzenbach
2020-08-25 17:33           ` Vinicius Costa Gomes
2020-08-24 22:56   ` Vladimir Oltean
2020-08-25  9:33     ` Kurt Kanzenbach
2020-08-25  9:38       ` Vladimir Oltean
2020-08-25  9:55         ` Kurt Kanzenbach
2020-08-27 16:25           ` Richard Cochran
2020-08-28 12:31             ` Kurt Kanzenbach
2020-08-24 23:57   ` Vinicius Costa Gomes
2020-08-25  9:23     ` Kurt Kanzenbach [this message]
2020-08-25  9:32       ` Vladimir Oltean
2020-09-01 14:20         ` Kurt Kanzenbach
2020-09-01 14:47           ` Vladimir Oltean
2020-08-25 17:50       ` Vinicius Costa Gomes
2020-08-20  8:11 ` [PATCH v3 6/8] net: dsa: hellcreek: Add PTP status LEDs Kurt Kanzenbach
2020-08-24 22:50   ` Andrew Lunn
2020-08-20  8:11 ` [PATCH v3 7/8] dt-bindings: Add vendor prefix for Hirschmann Kurt Kanzenbach
2020-08-20  8:11 ` [PATCH v3 8/8] dt-bindings: net: dsa: Add documentation for Hellcreek switches Kurt Kanzenbach
2020-08-24 22:52   ` Andrew Lunn
2020-08-25 22:28   ` Rob Herring
2020-08-24 21:31 ` [PATCH v3 0/8] Hirschmann Hellcreek DSA driver Jakub Kicinski
2020-08-24 22:02   ` Vladimir Oltean
2020-08-24 22:35     ` David Miller
2020-08-24 22:57       ` Vladimir Oltean
2020-08-25 11:21       ` Kurt Kanzenbach
2020-08-25 17:14         ` Florian Fainelli

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