From: Hector Martin <marcan@marcan.st>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>, SoC Team <soc@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Rob Herring <robh+dt@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
DTML <devicetree@vger.kernel.org>,
Olof Johansson <olof@lixom.net>
Subject: Re: [PATCH 10/18] arm64: Introduce FIQ support
Date: Tue, 9 Feb 2021 08:34:11 +0900 [thread overview]
Message-ID: <2eecb7cb-1065-9eab-adad-409f10906062@marcan.st> (raw)
In-Reply-To: <CAK8P3a1vmUJ0EpzU2+u2gy8WHCVV5ur9u-oTzU2BP=ddbXQeLQ@mail.gmail.com>
On 08/02/2021 03.49, Arnd Bergmann wrote:
> Ok, I had not realized the timer was level triggered. In case of the
> timer, I suppose it could be either masked or acknowledged from the
> fiq top-half handler when deferring to irq, but I agree that it means a
> layering violation in either case.
>
> What might still work is an approach where FIQ is normally enabled,
> and local_irq_disable() leaves it on, while local_irq_enable() turns
> it on regardless of the current state.
>
> In this case, the fiq handler could run the timer function if interrupts
> are enabled but just turn off fiqs when they are turned off, waiting
> for the next local_irq_enable() to get us back in the state where
> the handler can run. Not sure if that would buy us anything though,
> or if that still requires platform specific conditionals in common code.
It looks like Marc is just leaning towards making the IRQ and FIQ masks
track each other unconditionally on all platforms anyway, so I'm going
to try that for v2 (which is certainly the simpler solution). If this
ends up somehow breaking any other platform we can deal with it in the
way that makes most sense, once we know how it breaks :)
>> * An exception seems to be non-HV timer interrupts firing while we have
>> a VM guest running (HCR_EL2.TGE=0). This causes a single FIQ, and no
>> more, which suggests there is a mask bit for guest timer FIQs somewhere
>> that gets automatically set when the FIQ is delivered to the CPU core.
>> I've yet to find where this bit lives, I'll be doing a brute force sweep
>> of system register space soon to see if I can find it, and if there is
>> anything else useful near it.
>
> Right. Maybe you can even find a bit that switches between FIQ and
> IRQ mode for the timer, as that would solve the problem completely.
> I think it's not that rare for irqchips to be configurable to either route
> an interrupt one way or the other.
That seems increasingly unlikely here; I tried poking all the AIC config
bits and nothing switched those to FIQ (which is the converse). It looks
like Apple has done something like use FIQ for all core-internal
interrupt sources, and IRQ for AIC, and this is all seemingly quite
hardwired.
In particular, a subtlety I discovered about how flipping TGE to 1 with
a guest timer interrupt pending only takes effect properly (i.e. FIQ
fires, and you get a FIQ storm if unhandled, no auto-masking) after
subsequently issuing an isb, makes me think all this FIQ stuff is
seriously deeply tied into the instruction pipeline. It's probably not
an IRQ line any more...
--
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub
WARNING: multiple messages have this Message-ID (diff)
From: Hector Martin <marcan@marcan.st>
To: Arnd Bergmann <arnd@kernel.org>
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: Tue, 9 Feb 2021 08:34:11 +0900 [thread overview]
Message-ID: <2eecb7cb-1065-9eab-adad-409f10906062@marcan.st> (raw)
Message-ID: <20210208233411.A8A2HJvL1-gWqW9nO1YkQ9CfTrfz2IpP8eMY_2vC-80@z> (raw)
In-Reply-To: <CAK8P3a1vmUJ0EpzU2+u2gy8WHCVV5ur9u-oTzU2BP=ddbXQeLQ@mail.gmail.com>
On 08/02/2021 03.49, Arnd Bergmann wrote:
> Ok, I had not realized the timer was level triggered. In case of the
> timer, I suppose it could be either masked or acknowledged from the
> fiq top-half handler when deferring to irq, but I agree that it means a
> layering violation in either case.
>
> What might still work is an approach where FIQ is normally enabled,
> and local_irq_disable() leaves it on, while local_irq_enable() turns
> it on regardless of the current state.
>
> In this case, the fiq handler could run the timer function if interrupts
> are enabled but just turn off fiqs when they are turned off, waiting
> for the next local_irq_enable() to get us back in the state where
> the handler can run. Not sure if that would buy us anything though,
> or if that still requires platform specific conditionals in common code.
It looks like Marc is just leaning towards making the IRQ and FIQ masks
track each other unconditionally on all platforms anyway, so I'm going
to try that for v2 (which is certainly the simpler solution). If this
ends up somehow breaking any other platform we can deal with it in the
way that makes most sense, once we know how it breaks :)
>> * An exception seems to be non-HV timer interrupts firing while we have
>> a VM guest running (HCR_EL2.TGE=0). This causes a single FIQ, and no
>> more, which suggests there is a mask bit for guest timer FIQs somewhere
>> that gets automatically set when the FIQ is delivered to the CPU core.
>> I've yet to find where this bit lives, I'll be doing a brute force sweep
>> of system register space soon to see if I can find it, and if there is
>> anything else useful near it.
>
> Right. Maybe you can even find a bit that switches between FIQ and
> IRQ mode for the timer, as that would solve the problem completely.
> I think it's not that rare for irqchips to be configurable to either route
> an interrupt one way or the other.
That seems increasingly unlikely here; I tried poking all the AIC config
bits and nothing switched those to FIQ (which is the converse). It looks
like Apple has done something like use FIQ for all core-internal
interrupt sources, and IRQ for AIC, and this is all seemingly quite
hardwired.
In particular, a subtlety I discovered about how flipping TGE to 1 with
a guest timer interrupt pending only takes effect properly (i.e. FIQ
fires, and you get a FIQ storm if unhandled, no auto-masking) after
subsequently issuing an isb, makes me think all this FIQ stuff is
seriously deeply tied into the instruction pipeline. It's probably not
an IRQ line any more...
--
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub
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linux-arm-kernel mailing list
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next prev parent reply other threads:[~2021-02-08 23:35 UTC|newest]
Thread overview: 240+ 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 ` Hector Martin
2021-02-04 20:39 ` [PATCH 01/18] dt-bindings: vendor-prefixes: add AAPL prefix Hector Martin
2021-02-04 20:39 ` Hector Martin
2021-02-08 10:27 ` Krzysztof Kozlowski
2021-02-08 10:27 ` Krzysztof Kozlowski
2021-02-08 17:32 ` Rob Herring
2021-02-08 17:32 ` Rob Herring
2021-02-08 18:12 ` Krzysztof Kozlowski
2021-02-08 18:12 ` Krzysztof Kozlowski
2021-02-08 19:59 ` Arnd Bergmann
2021-02-08 19:59 ` Arnd Bergmann
2021-02-08 23:17 ` Hector Martin
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 02/18] dt-bindings: arm: cpus: Add AAPL, firestorm " 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 ` Hector Martin
2021-02-04 20:39 ` [PATCH 04/18] arm64: Kconfig: Introduce CONFIG_ARCH_APPLE Hector Martin
2021-02-04 20:39 ` Hector Martin
2021-02-06 13:17 ` Marc Zyngier
2021-02-06 13:17 ` Marc Zyngier
2021-02-07 8:05 ` Hector Martin 'marcan'
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 20:39 ` Hector Martin
2021-02-04 23:55 ` kernel test robot
2021-02-04 23:55 ` kernel test robot
2021-02-04 23:55 ` kernel test robot
2021-02-05 9:44 ` Hector Martin 'marcan'
2021-02-05 9:44 ` Hector Martin 'marcan'
2021-02-05 2:19 ` kernel test robot
2021-02-05 2:19 ` kernel test robot
2021-02-05 2:19 ` kernel test robot
2021-02-06 13:15 ` Marc Zyngier
2021-02-06 13:15 ` Marc Zyngier
2021-02-07 9:12 ` Hector Martin 'marcan'
2021-02-07 9:12 ` Hector Martin 'marcan'
2021-02-07 9:26 ` Hector Martin 'marcan'
2021-02-07 9:26 ` Hector Martin 'marcan'
2021-02-08 9:36 ` Krzysztof Kozlowski
2021-02-08 9:36 ` Krzysztof Kozlowski
2021-02-08 16:14 ` Hector Martin
2021-02-08 16:14 ` Hector Martin
2021-02-08 10:34 ` Marc Zyngier
2021-02-08 10:34 ` Marc Zyngier
2021-02-08 16:18 ` Hector Martin
2021-02-08 16:18 ` Hector Martin
2021-02-08 16:46 ` Greg Kroah-Hartman
2021-02-08 16:46 ` Greg Kroah-Hartman
2021-02-08 23:22 ` Hector Martin
2021-02-08 23:22 ` Hector Martin
2021-02-08 10:54 ` Krzysztof Kozlowski
2021-02-08 10:54 ` Krzysztof Kozlowski
2021-02-08 16:10 ` Hector Martin
2021-02-08 16:10 ` Hector Martin
2021-02-08 18:37 ` Krzysztof Kozlowski
2021-02-08 18:37 ` Krzysztof Kozlowski
2021-02-08 23:23 ` Hector Martin
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 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 20:39 ` Hector Martin
2021-02-04 21:16 ` Arnd Bergmann
2021-02-04 21:16 ` Arnd Bergmann
2021-02-04 21:27 ` Hector Martin 'marcan'
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
2021-02-04 20:39 ` Hector Martin
2021-02-06 13:58 ` Marc Zyngier
2021-02-06 13:58 ` Marc Zyngier
2021-02-07 8:28 ` Hector Martin 'marcan'
2021-02-07 8:28 ` Hector Martin 'marcan'
2021-02-08 11:29 ` Marc Zyngier
2021-02-08 11:29 ` Marc Zyngier
2021-02-08 15:51 ` Hector Martin
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 ` Hector Martin
2021-02-04 20:39 ` [PATCH 10/18] arm64: Introduce FIQ support Hector Martin
2021-02-04 20:39 ` Hector Martin
2021-02-06 15:37 ` Marc Zyngier
2021-02-06 15:37 ` Marc Zyngier
2021-02-06 16:22 ` Arnd Bergmann
2021-02-06 16:22 ` Arnd Bergmann
2021-02-07 8:36 ` Hector Martin 'marcan'
2021-02-07 8:36 ` Hector Martin 'marcan'
2021-02-07 12:25 ` Arnd Bergmann
2021-02-07 12:25 ` Arnd Bergmann
2021-02-07 15:38 ` Hector Martin 'marcan'
2021-02-07 15:38 ` Hector Martin 'marcan'
2021-02-07 18:49 ` Arnd Bergmann
2021-02-07 18:49 ` Arnd Bergmann
2021-02-08 23:34 ` Hector Martin [this message]
2021-02-08 23:34 ` Hector Martin
2021-02-07 8:47 ` Hector Martin 'marcan'
2021-02-07 8:47 ` Hector Martin 'marcan'
2021-02-08 11:30 ` Marc Zyngier
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
2021-02-04 20:39 ` Hector Martin
2021-02-06 15:46 ` Marc Zyngier
2021-02-06 15:46 ` Marc Zyngier
2021-02-07 9:23 ` Hector Martin 'marcan'
2021-02-07 9:23 ` Hector Martin 'marcan'
2021-02-08 12:05 ` Marc Zyngier
2021-02-08 12:05 ` Marc Zyngier
2021-02-08 15:48 ` Hector Martin
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 20:39 ` Hector Martin
2021-02-04 22:25 ` Arnd Bergmann
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 20:39 ` Hector Martin
2021-02-04 22:21 ` Arnd Bergmann
2021-02-04 22:21 ` Arnd Bergmann
2021-02-08 22:57 ` Arnd Bergmann
2021-02-08 22:57 ` Arnd Bergmann
2021-02-08 23:20 ` Mark Kettenis
2021-02-08 23:20 ` Mark Kettenis
2021-02-09 0:25 ` Hector Martin
2021-02-09 0:25 ` Hector Martin
2021-02-09 9:15 ` Arnd Bergmann
2021-02-09 9:15 ` Arnd Bergmann
2021-02-09 9:58 ` Mark Kettenis
2021-02-09 9:58 ` Mark Kettenis
2021-02-09 11:22 ` Hector Martin
2021-02-09 11:22 ` Hector Martin
2021-02-09 9:35 ` Arnd Bergmann
2021-02-09 9:35 ` Arnd Bergmann
2021-02-10 12:24 ` Hector Martin
2021-02-10 12:24 ` Hector Martin
2021-02-10 13:40 ` Mark Kettenis
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
2021-02-04 20:39 ` Hector Martin
2021-02-09 23:07 ` Rob Herring
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 20:39 ` Hector Martin
2021-02-04 21:37 ` Arnd Bergmann
2021-02-04 21:37 ` Arnd Bergmann
2021-02-04 22:04 ` Hector Martin 'marcan'
2021-02-04 22:04 ` Hector Martin 'marcan'
2021-02-04 23:04 ` Arnd Bergmann
2021-02-04 23:04 ` Arnd Bergmann
2021-02-05 7:41 ` Hector Martin 'marcan'
2021-02-05 7:41 ` Hector Martin 'marcan'
2021-02-05 10:33 ` Arnd Bergmann
2021-02-05 10:33 ` Arnd Bergmann
2021-02-05 2:27 ` kernel test robot
2021-02-05 2:27 ` kernel test robot
2021-02-05 2:27 ` kernel test robot
2021-02-05 9:45 ` Hector Martin 'marcan'
2021-02-05 9:45 ` Hector Martin 'marcan'
2021-02-08 9:25 ` Marc Zyngier
2021-02-08 9:25 ` Marc Zyngier
2021-02-08 10:29 ` Arnd Bergmann
2021-02-08 10:29 ` Arnd Bergmann
2021-02-08 11:13 ` Hector Martin 'marcan'
2021-02-08 11:13 ` Hector Martin 'marcan'
2021-02-08 11:21 ` Arnd Bergmann
2021-02-08 11:21 ` Arnd Bergmann
2021-02-08 11:36 ` Marc Zyngier
2021-02-08 11:36 ` Marc Zyngier
2021-02-08 12:17 ` Arnd Bergmann
2021-02-08 12:17 ` Arnd Bergmann
2021-02-08 15:31 ` Hector Martin
2021-02-08 15:31 ` Hector Martin
2021-02-09 6:20 ` 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 ` Hector Martin
2021-02-04 20:39 ` [PATCH 17/18] dt-bindings: display: add AAPL,simple-framebuffer Hector Martin
2021-02-04 20:39 ` Hector Martin
2021-02-04 20:39 ` [PATCH 18/18] arm64: apple: Add initial Mac Mini 2020 (M1) devicetree Hector Martin
2021-02-04 20:39 ` Hector Martin
2021-02-04 21:29 ` Arnd Bergmann
2021-02-04 21:29 ` Arnd Bergmann
2021-02-04 21:44 ` Hector Martin 'marcan'
2021-02-04 21:44 ` Hector Martin 'marcan'
2021-02-04 23:08 ` Arnd Bergmann
2021-02-04 23:08 ` Arnd Bergmann
2021-02-05 7:11 ` Hector Martin 'marcan'
2021-02-05 7:11 ` Hector Martin 'marcan'
2021-02-05 12:43 ` Arnd Bergmann
2021-02-05 12:43 ` Arnd Bergmann
2021-02-08 11:04 ` Krzysztof Kozlowski
2021-02-08 11:04 ` Krzysztof Kozlowski
2021-02-08 11:56 ` Hector Martin 'marcan'
2021-02-08 11:56 ` Hector Martin 'marcan'
2021-02-08 12:13 ` Krzysztof Kozlowski
2021-02-08 12:13 ` Krzysztof Kozlowski
2021-02-08 12:40 ` Arnd Bergmann
2021-02-08 12:40 ` Arnd Bergmann
2021-02-08 14:12 ` Hector Martin
2021-02-08 14:12 ` Hector Martin
2021-02-08 17:58 ` Rob Herring
2021-02-08 17:58 ` Rob Herring
2021-02-09 0:32 ` Hector Martin
2021-02-09 0:32 ` Hector Martin
2021-02-08 19:14 ` Rob Herring
2021-02-08 19:14 ` Rob Herring
2021-02-09 0:49 ` Hector Martin
2021-02-09 0:49 ` Hector Martin
2021-02-09 2:05 ` Rob Herring
2021-02-09 2:05 ` Rob Herring
2021-02-10 10:19 ` Tony Lindgren
2021-02-10 10:19 ` Tony Lindgren
2021-02-10 11:07 ` Hector Martin
2021-02-10 11:07 ` Hector Martin
2021-02-10 11:34 ` Tony Lindgren
2021-02-10 11:34 ` Tony Lindgren
2021-02-10 11:43 ` Hector Martin
2021-02-10 11:43 ` Hector Martin
2021-02-10 12:24 ` Daniel Palmer
2021-02-10 12:24 ` Daniel Palmer
2021-02-10 12:24 ` Daniel Palmer
2021-02-10 12:54 ` Tony Lindgren
2021-02-10 12:54 ` Tony Lindgren
2021-02-10 12:56 ` Hector Martin
2021-02-10 12:56 ` Hector Martin
2021-02-10 12:55 ` Krzysztof Kozlowski
2021-02-10 12:55 ` Krzysztof Kozlowski
2021-02-10 13:19 ` Tony Lindgren
2021-02-10 13:19 ` Tony Lindgren
2021-02-10 13:25 ` Krzysztof Kozlowski
2021-02-10 13:25 ` Krzysztof Kozlowski
2021-02-08 12:27 ` Marc Zyngier
2021-02-08 12:27 ` Marc Zyngier
2021-02-08 14:53 ` Hector Martin
2021-02-08 14:53 ` Hector Martin
2021-02-08 15:36 ` Marc Zyngier
2021-02-08 15:36 ` Marc Zyngier
2021-02-04 22:43 ` [PATCH 00/18] Apple M1 SoC platform bring-up Arnd Bergmann
2021-02-04 22:43 ` Arnd Bergmann
2021-02-05 11:35 ` Hector Martin 'marcan'
2021-02-05 11:35 ` Hector Martin 'marcan'
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