From: Arnd Bergmann <arnd@kernel.org>
To: "Hector Martin 'marcan'" <marcan@marcan.st>
Cc: DTML <devicetree@vger.kernel.org>, Marc Zyngier <maz@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
SoC Team <soc@kernel.org>, Rob Herring <robh+dt@kernel.org>,
Olof Johansson <olof@lixom.net>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 10/18] arm64: Introduce FIQ support
Date: Sun, 7 Feb 2021 13:25:03 +0100 [thread overview]
Message-ID: <CAK8P3a1R51_nqfMWG7SxScJNJEQ3qvp-cynABKEDaQ4O9REM=Q@mail.gmail.com> (raw)
In-Reply-To: <cb721f28-d5e9-3381-2d04-746c0aa2a0d3@marcan.st>
On Sun, Feb 7, 2021 at 9:36 AM Hector Martin 'marcan' <marcan@marcan.st> wrote:
> On 07/02/2021 01.22, Arnd Bergmann wrote:
> > * In the fiq handler code, check if normal interrupts were enabled
> > when the fiq hit. Normally they are enabled, so just proceed to
> > handle the timer and ipi directly
> >
> > * if irq was disabled, defer the handling by doing a self-ipi
> > through the aic's ipi method, and handle it from there
> > when dealing with the next interrupt once interrupts get
> > enabled.
> >
> > This would be similar to the soft-disable feature on powerpc, which
> > never actually turns off interrupts from regular kernel code but
> > just checks a flag in local_irq_enable that gets set when a
> > hardirq happened.
>
> Case #2 seems messy. In AIC, we'd have to either:
>
> * Disable FIQs, and hope that doesn't confuse any save/restore code
> going on, then set a flag and check it in *both* the IRQ and FIQ path
> since either might trigger depending on what happens next, or
> * Mask the relevant timer, which we'd then need to make sure does not
> confuse the timer code (Unmask it again when we fire the interrupt? But
> what if the timer code intended to mask it in the interim?)
I'm not quite following here. The IRQ should be disabled the entire time
while handling that self-IPI and the timer top half code, so if we get
another FIQ while handling the timer from the IRQ path, it will lead
either yet another self-IPI or it will be ignored in case the previous timer
event has not been Acked yet. I would expect that both cases are
race-free here, the only time that the FIQ needs to be disabled is
while actually handling the FIQ. Did I miss something?
> Plus I don't know if the vector entry code and other scaffolding between
> the vector and the AIC driver would be happy with, effectively,
> recursive interrupts. This could work with a carefully controlled path
> to make sure it doesn't break things, but I'm not so sure about the
> current "just point FIQ and IRQ to the same place" approach here.
If we do what I described above, the FIQ and IRQ entry would have
to be separate and only arrive in the same code path when calling
into drivers/clocksource/arm_arch_timer.c. It's not recursive there
because that part is only called when IRQ is disabled, and no IRQ
is being executed while the FIQ hits.
Arnd
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next prev parent reply other threads:[~2021-02-07 12:26 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 20:39 [PATCH 00/18] Apple M1 SoC platform bring-up Hector Martin
2021-02-04 20:39 ` [PATCH 01/18] dt-bindings: vendor-prefixes: add AAPL prefix Hector Martin
2021-02-08 10:27 ` Krzysztof Kozlowski
2021-02-08 17:32 ` Rob Herring
2021-02-08 18:12 ` Krzysztof Kozlowski
2021-02-08 19:59 ` Arnd Bergmann
2021-02-08 23:17 ` Hector Martin
2021-02-04 20:39 ` [PATCH 02/18] dt-bindings: arm: cpus: Add AAPL, firestorm & icestorm compatibles Hector Martin
2021-02-04 20:39 ` [PATCH 03/18] dt-bindings: arm: AAPL: Add bindings for Apple ARM platforms Hector Martin
2021-02-04 20:39 ` [PATCH 04/18] arm64: Kconfig: Introduce CONFIG_ARCH_APPLE Hector Martin
2021-02-06 13:17 ` Marc Zyngier
2021-02-07 8:05 ` Hector Martin 'marcan'
2021-02-04 20:39 ` [PATCH 05/18] tty: serial: samsung_tty: add support for Apple UARTs Hector Martin
2021-02-04 23:55 ` kernel test robot
2021-02-05 9:44 ` Hector Martin 'marcan'
2021-02-05 2:19 ` kernel test robot
2021-02-06 13:15 ` Marc Zyngier
2021-02-07 9:12 ` Hector Martin 'marcan'
2021-02-07 9:26 ` Hector Martin 'marcan'
2021-02-08 9:36 ` Krzysztof Kozlowski
2021-02-08 16:14 ` Hector Martin
2021-02-08 10:34 ` Marc Zyngier
2021-02-08 16:18 ` Hector Martin
2021-02-08 16:46 ` Greg Kroah-Hartman
2021-02-08 23:22 ` Hector Martin
2021-02-08 10:54 ` Krzysztof Kozlowski
2021-02-08 16:10 ` Hector Martin
2021-02-08 18:37 ` Krzysztof Kozlowski
2021-02-08 23:23 ` Hector Martin
2021-02-04 20:39 ` [PATCH 06/18] dt-bindings: serial: samsung: Add AAPL, s5l-uart compatible Hector Martin
2021-02-04 20:39 ` [PATCH 07/18] tty: serial: samsung_tty: enable for ARCH_APPLE Hector Martin
2021-02-04 21:16 ` Arnd Bergmann
2021-02-04 21:27 ` Hector Martin 'marcan'
2021-02-04 20:39 ` [PATCH 08/18] arm64: cpufeature: Add a feature for FIQ support Hector Martin
2021-02-06 13:58 ` Marc Zyngier
2021-02-07 8:28 ` Hector Martin 'marcan'
2021-02-08 11:29 ` Marc Zyngier
2021-02-08 15:51 ` Hector Martin
2021-02-04 20:39 ` [PATCH 09/18] arm64: cputype: Add CPU types for the Apple M1 big/little cores Hector Martin
2021-02-04 20:39 ` [PATCH 10/18] arm64: Introduce FIQ support Hector Martin
2021-02-06 15:37 ` Marc Zyngier
2021-02-06 16:22 ` Arnd Bergmann
2021-02-07 8:36 ` Hector Martin 'marcan'
2021-02-07 12:25 ` Arnd Bergmann [this message]
2021-02-07 15:38 ` Hector Martin 'marcan'
2021-02-07 18:49 ` Arnd Bergmann
2021-02-08 23:34 ` Hector Martin
2021-02-07 8:47 ` Hector Martin 'marcan'
2021-02-08 11:30 ` Marc Zyngier
2021-02-04 20:39 ` [PATCH 11/18] arm64: Kconfig: Require FIQ support for ARCH_APPLE Hector Martin
2021-02-06 15:46 ` Marc Zyngier
2021-02-07 9:23 ` Hector Martin 'marcan'
2021-02-08 12:05 ` Marc Zyngier
2021-02-08 15:48 ` Hector Martin
2021-02-04 20:39 ` [PATCH 12/18] arm64: setup: Use nGnRnE IO mappings for fixmap on Apple platforms Hector Martin
2021-02-04 22:25 ` Arnd Bergmann
2021-02-04 20:39 ` [PATCH 13/18] arm64: ioremap: use nGnRnE mappings on platforms that require it Hector Martin
2021-02-04 22:21 ` Arnd Bergmann
2021-02-08 22:57 ` Arnd Bergmann
2021-02-08 23:20 ` Mark Kettenis
2021-02-09 0:25 ` Hector Martin
2021-02-09 9:15 ` Arnd Bergmann
2021-02-09 9:58 ` Mark Kettenis
2021-02-09 11:22 ` Hector Martin
2021-02-09 9:35 ` Arnd Bergmann
2021-02-10 12:24 ` Hector Martin
2021-02-10 13:40 ` Mark Kettenis
2021-02-04 20:39 ` [PATCH 14/18] dt-bindings: interrupt-controller: Add DT bindings for apple-aic Hector Martin
2021-02-09 23:07 ` Rob Herring
2021-02-04 20:39 ` [PATCH 15/18] irqchip/apple-aic: Add support for the Apple Interrupt Controller Hector Martin
2021-02-04 21:37 ` Arnd Bergmann
2021-02-04 22:04 ` Hector Martin 'marcan'
2021-02-04 23:04 ` Arnd Bergmann
2021-02-05 7:41 ` Hector Martin 'marcan'
2021-02-05 10:33 ` Arnd Bergmann
2021-02-05 2:27 ` kernel test robot
2021-02-05 9:45 ` Hector Martin 'marcan'
2021-02-08 9:25 ` Marc Zyngier
2021-02-08 10:29 ` Arnd Bergmann
2021-02-08 11:13 ` Hector Martin 'marcan'
2021-02-08 11:21 ` Arnd Bergmann
2021-02-08 11:36 ` Marc Zyngier
2021-02-08 12:17 ` Arnd Bergmann
2021-02-08 15:31 ` Hector Martin
2021-02-09 6:20 ` Hector Martin
2021-02-04 20:39 ` [PATCH 16/18] irqchip/apple-aic: Add SMP / IPI support Hector Martin
2021-02-04 20:39 ` [PATCH 17/18] dt-bindings: display: add AAPL,simple-framebuffer Hector Martin
2021-02-04 20:39 ` [PATCH 18/18] arm64: apple: Add initial Mac Mini 2020 (M1) devicetree Hector Martin
2021-02-04 21:29 ` Arnd Bergmann
2021-02-04 21:44 ` Hector Martin 'marcan'
2021-02-04 23:08 ` Arnd Bergmann
2021-02-05 7:11 ` Hector Martin 'marcan'
2021-02-05 12:43 ` Arnd Bergmann
2021-02-08 11:04 ` Krzysztof Kozlowski
2021-02-08 11:56 ` Hector Martin 'marcan'
2021-02-08 12:13 ` Krzysztof Kozlowski
2021-02-08 12:40 ` Arnd Bergmann
2021-02-08 14:12 ` Hector Martin
2021-02-08 17:58 ` Rob Herring
2021-02-09 0:32 ` Hector Martin
2021-02-08 19:14 ` Rob Herring
2021-02-09 0:49 ` Hector Martin
2021-02-09 2:05 ` Rob Herring
2021-02-10 10:19 ` Tony Lindgren
2021-02-10 11:07 ` Hector Martin
2021-02-10 11:34 ` Tony Lindgren
2021-02-10 11:43 ` Hector Martin
2021-02-10 12:24 ` Daniel Palmer
2021-02-10 12:54 ` Tony Lindgren
2021-02-10 12:56 ` Hector Martin
2021-02-10 12:55 ` Krzysztof Kozlowski
2021-02-10 13:19 ` Tony Lindgren
2021-02-10 13:25 ` Krzysztof Kozlowski
2021-02-08 12:27 ` Marc Zyngier
2021-02-08 14:53 ` Hector Martin
2021-02-08 15:36 ` Marc Zyngier
2021-02-04 22:43 ` [PATCH 00/18] Apple M1 SoC platform bring-up Arnd Bergmann
2021-02-05 11:35 ` Hector Martin 'marcan'
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