From: Will Deacon <will@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Hector Martin <marcan@marcan.st>,
linux-kernel@vger.kernel.org,
Mohamed Mediouni <mohamed.mediouni@caramail.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Stan Skowronek <stan@corellium.com>
Subject: Re: [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors
Date: Thu, 21 Jan 2021 18:22:37 +0000 [thread overview]
Message-ID: <20210121182236.GC22963@willie-the-truck> (raw)
In-Reply-To: <f2b1cb981e7c3d42a9f815c2d2be08bb@kernel.org>
On Thu, Jan 21, 2021 at 06:15:06PM +0000, Marc Zyngier wrote:
> On 2021-01-21 17:55, Will Deacon wrote:
> > On Thu, Jan 21, 2021 at 04:25:54PM +0000, Marc Zyngier wrote:
> > > On 2021-01-21 15:12, Mohamed Mediouni wrote:
> > > > Please ignore that patch.
> > > >
> > > > It turns out that the PCIe controller on Apple M1 expects posted
> > > > writes and so the memory range for it ought to be set nGnRE.
> > > > So, we need to use nGnRnE for on-chip MMIO and nGnRE for PCIe BARs.
> > > >
> > > > The MAIR approach isn’t adequate for such a thing, so we’ll have to
> > > > look elsewhere.
> > >
> > > Well, there isn't many alternative to having a memory type defined
> > > in MAIR if you want to access your PCIe devices with specific
> > > semantics.
> > >
> > > It probably means defining a memory type for PCI only, but:
> > > - we only have a single free MT entry, and I'm not sure we can
> > > afford to waste this on a specific platform (can we re-purpose
> > > GRE instead?),
> >
> > We already have an nGnRnE MAIR for config space accesses.
>
> I'm confused. If M1 needs nGnRE for PCI, and overrides nGnRE to nE
> for its in-SoC accesses, where does nGnRE goes?
>
> Or do you propose that it is the page tables that get a different
> MT index?
Right, I'm just saying that we already have an nGnRnE MAIR configuration
so there's no need to worry about running out of entries if we need both
nGnRE and nGnRnE to co-exist. The nasty part is how to plumb this into
the mappings only for on-chip MMIO; I guess either a new API or we get
ioremap() to pick the memory type based on the address :/
Will
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next prev parent reply other threads:[~2021-01-21 18:24 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 13:27 [RFC PATCH 0/7] Linux on Apple Silicon Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 1/7] arm64: kernel: FIQ support Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 2/7] arm64: kernel: Add a WFI hook Mohamed Mediouni
2021-01-20 16:46 ` Alexander Graf
[not found] ` <94C20F55-D3B8-4349-B26F-9EA8AAEBF639@caramail.com>
2021-01-21 12:33 ` Hector Martin 'marcan'
2021-01-21 10:52 ` Arnd Bergmann
2021-01-21 11:01 ` Mohamed Mediouni
2021-01-21 11:36 ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors Mohamed Mediouni
2021-01-20 16:47 ` Alexander Graf
2021-01-20 18:06 ` Mohamed Mediouni
2021-01-20 18:10 ` Alexander Graf
2021-01-21 11:27 ` Will Deacon
2021-01-21 11:38 ` Arnd Bergmann
2021-01-21 11:44 ` Marc Zyngier
2021-01-21 12:47 ` Will Deacon
2021-01-21 15:12 ` Mohamed Mediouni
2021-01-21 16:25 ` Marc Zyngier
2021-01-21 17:55 ` Will Deacon
2021-01-21 18:15 ` Marc Zyngier
2021-01-21 18:22 ` Mohamed Mediouni
2021-01-21 18:22 ` Will Deacon [this message]
2021-01-20 13:27 ` [RFC PATCH 4/7] irqchip/apple-aic: Add support for Apple AIC Mohamed Mediouni
2021-01-20 17:11 ` Alexander Graf
2021-01-20 18:04 ` Mohamed Mediouni
2021-01-20 20:16 ` Andrew Lunn
2021-01-20 21:18 ` Stan Skowronek
2021-01-21 9:48 ` Linus Walleij
2021-01-21 10:37 ` Arnd Bergmann
2021-01-21 15:29 ` Hector Martin 'marcan'
2021-01-21 17:09 ` Rob Herring
2021-01-21 17:45 ` Rob Herring
2021-01-21 16:44 ` Rob Herring
2021-01-21 16:53 ` Hector Martin 'marcan'
2021-01-20 13:27 ` [RFC PATCH 5/7] arm64/Kconfig: Add Apple Silicon SoC platform Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 6/7] arm64: kernel: Apple CPU start driver Mohamed Mediouni
2021-01-21 11:14 ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver Mohamed Mediouni
2021-01-21 12:44 ` Arnd Bergmann
2021-01-21 12:50 ` Mohamed Mediouni
2021-01-21 13:00 ` Arnd Bergmann
2021-01-21 13:01 ` Hector Martin 'marcan'
2021-01-21 13:22 ` Marc Zyngier
2021-01-21 13:32 ` Mark Rutland
2021-01-21 14:05 ` Marc Zyngier
2021-01-21 13:34 ` Mohamed Mediouni
2021-01-21 14:10 ` Marc Zyngier
2021-01-21 15:09 ` Arnd Bergmann
2021-01-21 15:18 ` Mohamed Mediouni
2021-01-21 16:40 ` Rob Herring
2021-01-21 16:43 ` Mohamed Mediouni
2021-01-21 17:37 ` Rob Herring
2021-01-21 18:08 ` Mohamed Mediouni
2021-01-21 18:57 ` Rob Herring
2021-02-02 19:15 ` Linus Walleij
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