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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: DTML <devicetree@vger.kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	 Will Deacon <will@kernel.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	David Woodhouse <dwmw2@infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	 Christoph Hellwig <hch@infradead.org>,
	Rob Herring <robh+dt@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC 09/13] iommu/arm-smmu: Make use of dev_64bit_mmio_supported()
Date: Tue, 02 Mar 2021 13:42:16 +0100
Message-ID: <5ba9bdddbdee87d501b791309115c2eadaf9be84.camel@suse.de> (raw)
In-Reply-To: <CAK8P3a1t3yCD4vXF803nL=n3Y3hD1MOPOAEZwZA+782N64PXTA@mail.gmail.com>

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Hi Arnd, thanks for the reviews!

On Tue, 2021-03-02 at 10:32 +0100, Arnd Bergmann wrote:
> On Fri, Feb 26, 2021 at 3:03 PM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> wrote:
> 
> >         if (smmu->impl && unlikely(smmu->impl->write_reg))
> >                 smmu->impl->write_reg(smmu, page, offset, val);
> > -       else
> > +       else if (dev_64bit_mmio_supported(smmu->dev))
> >                 writel_relaxed(val, arm_smmu_page(smmu, page) + offset);
> > +       else
> > +               hi_lo_writeq_relaxed(val, arm_smmu_page(smmu, page) + offset);
> >  }
> 
> This is a writel_relaxed(), not a writeq_relaxed(), so I suppose you don't
> have to change it at all.

Yes, that was silly of me. I was worrying about the semantics of the whole
thing, and missed basic stuff like this.

> > +       else if (dev_64bit_mmio_supported(smmu->dev))
> > +               return readq_relaxed(arm_smmu_page(smmu, page) + offset);
> > +       else
> > +               return hi_lo_readq_relaxed(arm_smmu_page(smmu, page) + offset);
> > }
> 
> 
> I see this pattern repeat across multiple drivers. I think Christoph
> had originally
> suggested folding the if/else logic into the writel_relaxed() that is defined in
> include/linux/io-64-nonatomic-hi-lo.h, but of course that doesn't work if you
> need to pass a device pointer.
> 
> It might still make sense to have another wrapper in that same file though,
> something like
> 
> static inline hi_lo_writeq_relaxed_if_possible(struct device *dev, __u64 val,
>                     volatile void __iomem *addr)
> {
>        if (dev_64bit_mmio_supported(smmu->dev)) {
>               readq_relaxed(arm_smmu_page(smmu, page) + offset);
>        } else {
>                writel_relaxed(val >> 32, addr + 4);
>                writel_relaxed(val, addr);
>        }
> }

I like the idea. I'll try to integrate it into the next revision.

Regards,
Nicolas


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Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-26 14:02 [RFC 00/13] Generic way of dealing with broken 64-bit buses Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 01/13] dt-bindings: Introduce 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 02/13] driver core: Introduce MMIO configuration Nicolas Saenz Julienne
2021-03-02 11:29   ` Robin Murphy
2021-03-02 14:09     ` Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 03/13] of: device: Introduce of_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 04/13] driver core: plafrom: Introduce platform_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 05/13] pci: Introduce pci_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 06/13] device core: Introduce dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 07/13] arm64: Mark ARCH_MVEBU as needing broken 64bit MMIO support Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 08/13] arm64: dts: marvell: armada-ap80x: Mark config-space bus as 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 09/13] iommu/arm-smmu: Make use of dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-03-02  9:32   ` Arnd Bergmann
2021-03-02 12:42     ` Nicolas Saenz Julienne [this message]
2021-03-02 11:07   ` Robin Murphy
2021-03-02 13:38     ` Nicolas Saenz Julienne
2021-03-03  8:44     ` Arnd Bergmann
2021-02-26 14:03 ` [RFC 10/13] iommu/arm-smmu-impl: Get rid of Marvell's implementation details Nicolas Saenz Julienne
2021-03-02 11:40   ` Robin Murphy
2021-03-02 14:06     ` Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 11/13] arm64: Mark ARCH_BCM2835 as needing broken 64bit MMIO support Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 12/13] ARM: dts: bcm2711: Mark PCIe bus as 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 13/13] scsi: megaraid: Make use of dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-02-26 14:30   ` Arnd Bergmann
2021-02-26 18:06     ` Arnd Bergmann

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