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From: Marc Zyngier <maz@kernel.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: DTML <devicetree@vger.kernel.org>,
	Hector Martin <marcan@marcan.st>,
	"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 15/18] irqchip/apple-aic: Add support for the Apple Interrupt Controller
Date: Mon, 08 Feb 2021 11:36:02 +0000	[thread overview]
Message-ID: <87a6selrkt.wl-maz@kernel.org> (raw)
In-Reply-To: <CAK8P3a25eFFrMG-9QknFZ6Ckc3-gkiLK=jQdnyTMgn-z4X0RHQ@mail.gmail.com>

On Mon, 08 Feb 2021 10:29:23 +0000,
Arnd Bergmann <arnd@kernel.org> wrote:
> 
> On Mon, Feb 8, 2021 at 10:25 AM Marc Zyngier <maz@kernel.org> wrote:
> > On Thu, 04 Feb 2021 20:39:48 +0000, Hector Martin <marcan@marcan.st> wrote:
> 
> > > +{
> > > +     return readl(ic->base + reg);
> >
> > Please consider using the _relaxed accessors, as I don't think any of
> > these interacts with memory (apart from IPIs, of course).
> 
> MSI interrupts require serializing with DMA, so at the minimum I think there
> needs to be something that ensures that DMA from device into memory
> has completed before delivering the completion interrupt to a driver. This
> may already be implied when the AIC is entered, but this is hard to know
> without actual hardware specs.

If there is a sync with memory required, it should happen at the point
where it is Acked, not when masked/unmasked or anything else. And
given that you want to sync with an external agent (the DMA producer),
the DMB generated by readl won't save you, as it only orders CPU
accesses AFAICT.

So if MSIs require some additional synchronisation we probably need a
DSB somewhere if the HW doesn't guarantee ordering of DMA vs
MSIs. Whether it does or not is anyone's bet.

Thanks,

	M.

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

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  parent reply	other threads:[~2021-02-08 11:37 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
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 [this message]
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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