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From: Thomas Gleixner <tglx@linutronix.de>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Maarten ter Huurne <maarten@treewalker.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	od@zcrc.me, linux-kernel@vger.kernel.org,
	Mathieu Malaterre <malat@debian.org>,
	Artur Rojek <contact@artur-rojek.eu>
Subject: Re: [PATCH v3] clocksource: Add driver for the Ingenic JZ47xx OST
Date: Wed, 15 Jan 2020 22:50:19 +0100	[thread overview]
Message-ID: <87muaoxuck.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1579121936.3.1@crapouillou.net>

Paul Cercueil <paul@crapouillou.net> writes:
> Le mer., janv. 15, 2020 at 20:54, Thomas Gleixner <tglx@linutronix.de> 
>> That lock still a massive contention point as clock readouts can be 
>> pretty
>> frequent depending on workloads. Just think about tracing ...
>> 
>> So I really would avoid both the lock and that ugly 64bit readout 
>> thing.
>
> The 64bit readout thing is gone in V3.
>
> The lock cannot go away unless we have a way to retrieve the underlying 
> mmio pointer from the regmap, which the regmap maintainers will never 
> accept. So I can't really change that now. Besides, 
> drivers/clocksource/ingenic-timer.c also registers a clocksource that's 
> read with the regmap, and nobody complained.

I don't complain. I just told you that a spinlock in that code path is
really suboptimal.

I missed the one in the other driver, but the same problem exists there.

Thanks,

        tglx

  reply	other threads:[~2020-01-15 21:50 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 15:06 [PATCH v3] clocksource: Add driver for the Ingenic JZ47xx OST Paul Cercueil
2020-01-15 13:44 ` Daniel Lezcano
2020-01-15 13:57   ` Paul Cercueil
2020-01-15 17:48     ` Maarten ter Huurne
2020-01-15 17:54       ` Paul Cercueil
2020-01-15 19:54         ` Thomas Gleixner
2020-01-15 20:58           ` Paul Cercueil
2020-01-15 21:50             ` Thomas Gleixner [this message]
2020-02-08  7:09             ` Daniel Lezcano
2020-02-08 13:23               ` Paul Cercueil

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