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From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oupton@google.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Shier <pshier@google.com>,
	Raghavendra Rao Ananta <rananta@google.com>,
	Ricardo Koller <ricarkol@google.com>
Subject: Re: [PATCH v2] clocksource/arm_arch_timer: Fix masking for high freq counters
Date: Sun, 08 Aug 2021 11:40:30 +0100	[thread overview]
Message-ID: <87lf5c1aox.wl-maz@kernel.org> (raw)
In-Reply-To: <CAOQ_QsiECN7iVDyiyos12tk__viGkFhH9b6ZfkZVAYjeKhB=pQ@mail.gmail.com>

On Sun, 08 Aug 2021 02:14:35 +0100,
Oliver Upton <oupton@google.com> wrote:

> The only other sane idea that I could come up with is providing this
> information to the kernel through DT, although that would leave ACPI
> systems behind.

It also has the disadvantage that a large number of DT timer nodes are
a mess of cargo-culted, copy-pasted idioms, and that adding another
property would only make it worse. I'm more confident with something
that can be either:

- checked from EL2 using CNTVOFF, which is complicated, doesn't work
  at EL1, and leaves us in a weird state if we have different counter
  width views in the system (BL is such a wonderful concept)

- or computed from first principle based on the requirements of the
  architecture.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oupton@google.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Shier <pshier@google.com>,
	Raghavendra Rao Ananta <rananta@google.com>,
	Ricardo Koller <ricarkol@google.com>
Subject: Re: [PATCH v2] clocksource/arm_arch_timer: Fix masking for high freq counters
Date: Sun, 08 Aug 2021 11:40:30 +0100	[thread overview]
Message-ID: <87lf5c1aox.wl-maz@kernel.org> (raw)
In-Reply-To: <CAOQ_QsiECN7iVDyiyos12tk__viGkFhH9b6ZfkZVAYjeKhB=pQ@mail.gmail.com>

On Sun, 08 Aug 2021 02:14:35 +0100,
Oliver Upton <oupton@google.com> wrote:

> The only other sane idea that I could come up with is providing this
> information to the kernel through DT, although that would leave ACPI
> systems behind.

It also has the disadvantage that a large number of DT timer nodes are
a mess of cargo-culted, copy-pasted idioms, and that adding another
property would only make it worse. I'm more confident with something
that can be either:

- checked from EL2 using CNTVOFF, which is complicated, doesn't work
  at EL1, and leaves us in a weird state if we have different counter
  width views in the system (BL is such a wonderful concept)

- or computed from first principle based on the requirements of the
  architecture.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-08-08 10:42 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-07 19:14 [PATCH v2] clocksource/arm_arch_timer: Fix masking for high freq counters Oliver Upton
2021-08-07 19:14 ` Oliver Upton
2021-08-07 22:30 ` Linus Walleij
2021-08-07 22:30   ` Linus Walleij
2021-08-08  1:14   ` Oliver Upton
2021-08-08  1:14     ` Oliver Upton
2021-08-08 10:40     ` Marc Zyngier [this message]
2021-08-08 10:40       ` Marc Zyngier
2021-08-08 19:01       ` Oliver Upton
2021-08-08 19:01         ` Oliver Upton
2021-08-09 10:45         ` Marc Zyngier
2021-08-09 10:45           ` Marc Zyngier
2021-08-09 15:08           ` Oliver Upton
2021-08-09 15:08             ` Oliver Upton
2021-08-08 10:29   ` Marc Zyngier
2021-08-08 10:29     ` Marc Zyngier
2021-08-09 11:07 ` Marc Zyngier
2021-08-09 11:07   ` Marc Zyngier
2021-10-24 15:39 ` [tip: timers/core] clocksource/drivers/arm_arch_timer: " tip-bot2 for Oliver Upton

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