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From: Kurt Kanzenbach <kurt@linutronix.de>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
"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
Subject: Re: [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support
Date: Tue, 25 Aug 2020 11:55:37 +0200 [thread overview]
Message-ID: <871rjv123q.fsf@kurt> (raw)
In-Reply-To: <20200825093830.r2zlpowtmhgwm6rz@skbuf>
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On Tue Aug 25 2020, Vladimir Oltean wrote:
> On Tue, Aug 25, 2020 at 11:33:53AM +0200, Kurt Kanzenbach wrote:
>> On Tue Aug 25 2020, Vladimir Oltean wrote:
>> > On Thu, Aug 20, 2020 at 10:11:15AM +0200, Kurt Kanzenbach wrote:
>> >
>> > Explain again how this works, please? The hrtimer measures the CLOCK_TAI
>> > of the CPU, but you are offloading the CLOCK_TAI domain of the NIC? So
>> > you are assuming that the CPU and the NIC PHC are synchronized? What if
>> > they aren't?
>>
>> Yes, I assume that's synchronized with e.g. phc2sys.
>>
>
> My intuition tells me that this isn't the user's expectation, and that
> it should do the right thing even if it's not synchronized to the system
> clock.
I get your point. But how to do it? We would need a timer based on the
PTP clock in the switch.
>
>> >
>> > And what if the base-time is in the past, do you deal with that (how
>> > does the hardware deal with a base-time in the past)?
>> > A base-time in the past (example: 0) should work: you should advance the
>> > base-time into the nearest future multiple of the cycle-time, to at
>> > least preserve phase correctness of the schedule.
>>
>> If the hrtimer is programmed with a value in the past, it fires
>> instantly.
>
> Yes, it does.
>
>> The callback is executed and the start time is programmed.
>>
>
> With a valid value from the hardware's perspective?
Yes. That's no problem.
Thanks,
Kurt
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next prev parent reply other threads:[~2020-08-25 9:55 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 [this message]
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
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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