From: Jon Hunter <jonathanh@nvidia.com>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
John <therealgraysky@proton.me>,
Daniel Drake <dan@reactivated.net>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Florian Fainelli <florian.fainelli@broadcom.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Mark Rutland <mark.rutland@arm.com>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: Workaround bcm2712 broken EL2 virtual timer
Date: Thu, 23 Jul 2026 11:22:54 +0100 [thread overview]
Message-ID: <e5a32fcc-ca3c-4b54-a790-d2eef2c636e5@nvidia.com> (raw)
In-Reply-To: <865x26do37.wl-maz@kernel.org>
On 23/07/2026 10:58, Marc Zyngier wrote:
...
>>>> I have posted something similar for Tegra [0], but because this is not
>>>> expected to work, I wanted to avoid the warnings here. We test for
>>>
>>> "not expected to work"? In which parallel universe is that a thing?
>>
>> FWIU, at least for Tegra194, we have a CPU and GIC pairing where the
>> CPU supports this but the GIC does not.
>
> Oh please, you know better than this.
>
> It isn't the GIC that defines the number of supported PPIs, it is the
> *integrator*. I.e. you. The GIC (GIC400 in this example) has full
> support for 16 PPIs per CPU.
Hmmm, I am looking at this spec [0] and it says ...
"The GIC-400 implements the interrupt types:
16 Software Generated Interrupts (SGIs).
6 external Private Peripheral Interrupts (PPIs) for each processor.
1 internal PPI for each processor."
The table in [1] shows interrupts for non-sec, sec, virt and hypervisor
timers, but I don't see a hyp-virt.
> I have a collection of VHE-capable machines with GIC400 that correctly
> implement the EL2 virtual timer PPI (if even Amlogic and AllWinner can
> get this right, really *anybody* can). My conclusion is that someone
> couldn't be bothered to drag a wire from one end to the other.
OK, so most likely I am still missing something here.
[0]
https://developer.arm.com/documentation/ddi0471/b/introduction/about-the-gic-400?lang=en
[1]
https://developer.arm.com/documentation/ddi0471/b/functional-description/interrupt-inputs-to-the-gic-400/ppis?lang=en
--
nvpublic
next prev parent reply other threads:[~2026-07-23 10:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260710080958.491620-1-maz@kernel.org>
2026-07-22 14:14 ` [PATCH] clocksource/drivers/arm_arch_timer: Workaround bcm2712 broken EL2 virtual timer Jon Hunter
2026-07-22 20:22 ` Marc Zyngier
2026-07-23 9:24 ` Jon Hunter
2026-07-23 9:58 ` Marc Zyngier
2026-07-23 10:22 ` Jon Hunter [this message]
2026-07-23 10:46 ` Marc Zyngier
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=e5a32fcc-ca3c-4b54-a790-d2eef2c636e5@nvidia.com \
--to=jonathanh@nvidia.com \
--cc=dan@reactivated.net \
--cc=daniel.lezcano@linaro.org \
--cc=florian.fainelli@broadcom.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tegra@vger.kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=tglx@linutronix.de \
--cc=therealgraysky@proton.me \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox