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From: Arnd Bergmann <arnd@kernel.org>
To: Rob Herring <robh@kernel.org>
Cc: Hector Martin <marcan@marcan.st>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Marc Zyngier <maz@kernel.org>, Olof Johansson <olof@lixom.net>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Mark Kettenis <mark.kettenis@xs4all.nl>,
	Tony Lindgren <tony@atomide.com>,
	Mohamed Mediouni <mohamed.mediouni@caramail.com>,
	Stan Skowronek <stan@corellium.com>,
	Alexander Graf <graf@amazon.com>, Will Deacon <will@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christoph Hellwig <hch@infradead.org>,
	"David S. Miller" <davem@davemloft.net>,
	DTML <devicetree@vger.kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"open list:GENERIC INCLUDE/ASM HEADER FILES" 
	<linux-arch@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted
Date: Thu, 11 Mar 2021 10:12:02 +0100	[thread overview]
Message-ID: <CAK8P3a2HWbHc-aGHk792TVh6ea2j+aKswYrB6EBsjPA6fH1=xA@mail.gmail.com> (raw)
In-Reply-To: <CAL_Jsq+X7JPm-xrxmy5bGKSuLO59yk6S=EuXmdMn0FwhpZAD7A@mail.gmail.com>

On Wed, Mar 10, 2021 at 6:01 PM Rob Herring <robh@kernel.org> wrote:
>
> On Wed, Mar 10, 2021 at 1:27 AM Hector Martin <marcan@marcan.st> wrote:
> >
> > On 10/03/2021 07.06, Rob Herring wrote:
> > >> My main concern here is that this creates an inconsistency in the device
> > >> tree representation that only works because PCI drivers happen not to
> > >> use these code paths. Logically, having "nonposted-mmio" above the PCI
> > >> controller would imply that it applies to that bus too. Sure, it doesn't
> > >> matter for Linux since it is ignored, but this creates an implicit
> > >> exception that PCI buses always use posted modes.
> > >
> > > We could be stricter that "nonposted-mmio" must be in the immediate
> > > parent. That's kind of in line with how addressing already works.
> > > Every level has to have 'ranges' to be an MMIO address, and the
> > > address cell size is set by the immediate parent.
> > >
> > >> Then if a device comes along that due to some twisted fabric logic needs
> > >> nonposted nGnRnE mappings for PCIe (even though the actual PCIe ops will
> > >> end up posted at the bus anyway)... how do we represent that? Declare
> > >> that another "nonposted-mmio" on the PCIe bus means "no, really, use
> > >> nonposted mmio for this"?
> > >
> > > If we're strict, yes. The PCI host bridge would have to have "nonposted-mmio".
> >
> > Works for me; then let's just make it non-recursive.
> >
> > Do you think we can get rid of the Apple-only optimization if we do
> > this? It would mean only looking at the parent during address
> > resolution, not recursing all the way to the top, so presumably the
> > performance impact would be quite minimal.

Works for me.

> Yeah, that should be fine. I'd keep an IS_ENABLED() config check
> though. Then I'll also know if anyone else needs this.

Ok, makes sense.

Conceptually, I'd like to then see a check that verifies that the
property is only set for nodes whose parent also has it set, since
that is how AXI defines it: A bus can wait for the ack from its
child node, or it can acknowledge the write to its parent early.
However, this breaks down as soon as a bus does the early ack:
all its children by definition use posted writes (as seen by the
CPU), even if they wait for stores that come from other masters.

Does this make sense to you?

       Arnd

  reply	other threads:[~2021-03-11  9:13 UTC|newest]

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04 21:38 [RFT PATCH v3 00/27] Apple M1 SoC platform bring-up Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 01/27] arm64: Cope with CPUs stuck in VHE mode Hector Martin
2021-03-24 18:05   ` Will Deacon
2021-03-24 20:00     ` Marc Zyngier
2021-03-26  7:54       ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 02/27] dt-bindings: vendor-prefixes: Add apple prefix Hector Martin
2021-03-08 20:26   ` Rob Herring
2021-03-04 21:38 ` [RFT PATCH v3 03/27] dt-bindings: arm: apple: Add bindings for Apple ARM platforms Hector Martin
2021-03-05 10:16   ` Linus Walleij
2021-03-08 20:27   ` Rob Herring
2021-03-04 21:38 ` [RFT PATCH v3 04/27] dt-bindings: arm: cpus: Add apple,firestorm & icestorm compatibles Hector Martin
2021-03-08 20:27   ` Rob Herring
2021-03-04 21:38 ` [RFT PATCH v3 05/27] arm64: cputype: Add CPU implementor & types for the Apple M1 cores Hector Martin
2021-03-24 18:13   ` Will Deacon
2021-03-04 21:38 ` [RFT PATCH v3 06/27] dt-bindings: timer: arm,arch_timer: Add interrupt-names support Hector Martin
2021-03-05 10:18   ` Linus Walleij
2021-03-08 11:12   ` Marc Zyngier
2021-03-08 17:14   ` Tony Lindgren
2021-03-08 20:38   ` Rob Herring
2021-03-08 22:42     ` Marc Zyngier
2021-03-09 16:11       ` Rob Herring
2021-03-09 20:28         ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 07/27] arm64: arch_timer: implement support for interrupt-names Hector Martin
2021-03-05 10:19   ` Linus Walleij
2021-03-08 11:13   ` Marc Zyngier
2021-03-04 21:38 ` [RFT PATCH v3 08/27] asm-generic/io.h: Add a non-posted variant of ioremap() Hector Martin
2021-03-05 14:45   ` Andy Shevchenko
2021-03-05 15:19     ` Hector Martin
2021-03-08 11:20   ` Marc Zyngier
2021-03-24 18:12   ` Will Deacon
2021-03-24 19:09     ` Arnd Bergmann
2021-03-25 14:07       ` Hector Martin
2021-03-25 14:49         ` Will Deacon
2021-03-04 21:38 ` [RFT PATCH v3 09/27] docs: driver-api: device-io: Document I/O access functions Hector Martin
2021-03-05 10:22   ` Linus Walleij
2021-03-04 21:38 ` [RFT PATCH v3 10/27] docs: driver-api: device-io: Document ioremap() variants & access funcs Hector Martin
2021-03-05 10:25   ` Linus Walleij
2021-03-05 15:09     ` Andy Shevchenko
2021-03-05 15:51       ` Arnd Bergmann
2021-03-09 20:29         ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 11/27] arm64: Implement ioremap_np() to map MMIO as nGnRnE Hector Martin
2021-03-08 11:22   ` Marc Zyngier
2021-03-24 18:18   ` Will Deacon
2021-03-04 21:38 ` [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted Hector Martin
2021-03-05 10:28   ` Linus Walleij
2021-03-05 15:13   ` Andy Shevchenko
2021-03-05 15:55     ` Hector Martin
2021-03-05 16:08       ` Andy Shevchenko
2021-03-05 16:43         ` Arnd Bergmann
2021-03-05 17:19           ` Hector Martin
2021-03-05 16:05     ` Rob Herring
2021-03-05 17:39   ` Rob Herring
2021-03-05 18:18     ` Hector Martin
2021-03-05 21:17       ` Arnd Bergmann
2021-03-08 15:56         ` Rob Herring
2021-03-08 20:29           ` Arnd Bergmann
2021-03-08 21:13             ` Rob Herring
2021-03-08 21:56               ` Arnd Bergmann
2021-03-09 15:48                 ` Rob Herring
2021-03-09 20:23                   ` Hector Martin
2021-03-09 22:06                     ` Rob Herring
2021-03-10  8:26                       ` Hector Martin
2021-03-10 17:01                         ` Rob Herring
2021-03-11  9:12                           ` Arnd Bergmann [this message]
2021-03-11 12:11                             ` Hector Martin
2021-03-11 13:35                               ` Arnd Bergmann
2021-03-11 16:07                             ` Rob Herring
2021-03-11 16:48                               ` Arnd Bergmann
2021-03-11 18:10                                 ` Rob Herring
2021-03-12 10:20                                   ` Arnd Bergmann
2021-03-09 11:14               ` Linus Walleij
2021-03-09 12:41                 ` Arnd Bergmann
2021-03-09 15:40                   ` Linus Walleij
2021-03-04 21:38 ` [RFT PATCH v3 13/27] arm64: Add Apple vendor-specific system registers Hector Martin
2021-03-24 18:38   ` Will Deacon
2021-03-24 18:59     ` Mark Rutland
2021-03-24 19:04       ` Will Deacon
2021-03-26  6:23         ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 14/27] arm64: move ICH_ sysreg bits from arm-gic-v3.h to sysreg.h Hector Martin
2021-03-08 11:39   ` Marc Zyngier
2021-03-24 18:23   ` Will Deacon
2021-03-04 21:38 ` [RFT PATCH v3 15/27] dt-bindings: interrupt-controller: Add DT bindings for apple-aic Hector Martin
2021-03-08 21:16   ` Rob Herring
2021-03-04 21:38 ` [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller Hector Martin
2021-03-05 15:05   ` Andy Shevchenko
2021-03-08 11:50     ` Marc Zyngier
2021-03-08 12:02       ` Andy Shevchenko
2021-03-26 13:40     ` Hector Martin
2021-03-08 13:31   ` Marc Zyngier
2021-03-26  7:57     ` Hector Martin
2021-03-24 19:57   ` Will Deacon
2021-03-26  8:58     ` Hector Martin
2021-03-29 12:04       ` Will Deacon
2021-04-01 13:16         ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 17/27] arm64: Kconfig: Introduce CONFIG_ARCH_APPLE Hector Martin
2021-03-08 15:35   ` Marc Zyngier
2021-03-09 20:30     ` Hector Martin
2021-03-04 21:38 ` [RFT PATCH v3 18/27] tty: serial: samsung_tty: Separate S3C64XX ops structure Hector Martin
2021-03-05 10:30   ` Krzysztof Kozlowski
2021-03-04 21:38 ` [RFT PATCH v3 19/27] tty: serial: samsung_tty: Add ucon_mask parameter Hector Martin
2021-03-05 10:34   ` Krzysztof Kozlowski
2021-03-04 21:38 ` [RFT PATCH v3 20/27] tty: serial: samsung_tty: Add s3c24xx_port_type Hector Martin
2021-03-05 10:49   ` Krzysztof Kozlowski
2021-03-04 21:38 ` [RFT PATCH v3 21/27] tty: serial: samsung_tty: IRQ rework Hector Martin
2021-03-05 10:51   ` Krzysztof Kozlowski
2021-03-05 15:17   ` Andy Shevchenko
2021-03-05 16:16     ` Hector Martin
2021-03-05 16:20       ` Andy Shevchenko
2021-03-05 16:29         ` Hector Martin
2021-03-07 11:34           ` Krzysztof Kozlowski
2021-03-07 16:01             ` Arnd Bergmann
2021-03-07 19:51               ` Krzysztof Kozlowski
2021-03-04 21:38 ` [RFT PATCH v3 22/27] tty: serial: samsung_tty: Use devm_ioremap_resource Hector Martin
2021-03-05 10:54   ` Krzysztof Kozlowski
2021-03-05 15:19     ` Andy Shevchenko
2021-03-04 21:38 ` [RFT PATCH v3 23/27] dt-bindings: serial: samsung: Add apple,s5l-uart compatible Hector Martin
2021-03-08 21:17   ` Rob Herring
2021-03-04 21:38 ` [RFT PATCH v3 24/27] tty: serial: samsung_tty: Add support for Apple UARTs Hector Martin
2021-03-05 10:58   ` Krzysztof Kozlowski
2021-03-05 15:28   ` Andy Shevchenko
2021-03-05 17:04     ` Hector Martin
2021-03-07 11:40       ` Krzysztof Kozlowski
2021-03-04 21:39 ` [RFT PATCH v3 25/27] tty: serial: samsung_tty: Add earlycon " Hector Martin
2021-03-05 10:55   ` Krzysztof Kozlowski
2021-03-10 23:11   ` Linus Walleij
2021-03-04 21:39 ` [RFT PATCH v3 26/27] dt-bindings: display: Add apple,simple-framebuffer Hector Martin
2021-03-08 21:18   ` Rob Herring
2021-03-09 16:37   ` Linus Walleij
2021-03-09 20:35     ` Hector Martin
2021-03-04 21:39 ` [RFT PATCH v3 27/27] arm64: apple: Add initial Apple Mac mini (M1, 2020) devicetree Hector Martin
2021-03-05 11:03   ` Krzysztof Kozlowski
2021-03-05 11:14     ` Hector Martin
2021-03-05 11:45       ` Krzysztof Kozlowski
2021-03-05 15:59       ` Mark Kettenis
2021-03-05 16:50         ` Hector Martin
2021-03-05 10:11 ` [RFT PATCH v3 00/27] Apple M1 SoC platform bring-up Hector Martin

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